Merge remote-tracking branch 'notes/main'

26 files changed, 1677 insertions, 0 deletions

diff --git a/users/fcuny/notes/.drone.yml b/users/fcuny/notes/.drone.yml
new file mode 100644
index 0000000..ee50017
--- /dev/null
+++ b/users/fcuny/notes/.drone.yml
@@ -0,0 +1,18 @@
+---
+kind: pipeline
+type: exec
+name: default
+
+trigger:
+  event:
+    - push
+  branch:
+    - main
+
+steps:
+  - name: deploy
+    environment:
+      FLY_API_TOKEN:
+        from_secret: FLY_API_TOKEN
+    commands:
+      - nix run .#deploy
diff --git a/users/fcuny/notes/.envrc b/users/fcuny/notes/.envrc
new file mode 100644
index 0000000..3550a30
--- /dev/null
+++ b/users/fcuny/notes/.envrc
@@ -0,0 +1 @@
+use flake
diff --git a/users/fcuny/notes/.gitignore b/users/fcuny/notes/.gitignore
new file mode 100644
index 0000000..a85694c
--- /dev/null
+++ b/users/fcuny/notes/.gitignore
@@ -0,0 +1,2 @@
+/docs/
+/.hugo_build.lock
diff --git a/users/fcuny/notes/Dockerfile b/users/fcuny/notes/Dockerfile
new file mode 100644
index 0000000..64c0f97
--- /dev/null
+++ b/users/fcuny/notes/Dockerfile
@@ -0,0 +1,7 @@
+FROM klakegg/hugo:0.91.2-ext-alpine-onbuild AS hugo
+
+FROM pierrezemb/gostatic
+
+COPY --from=hugo /target /srv/http/
+
+CMD ["-port", "8080" , "-https-promote"]
diff --git a/users/fcuny/notes/archetypes/default.md b/users/fcuny/notes/archetypes/default.md
new file mode 100644
index 0000000..7ce2f1a
--- /dev/null
+++ b/users/fcuny/notes/archetypes/default.md
@@ -0,0 +1,5 @@
+---
+title: "{{ replace .Name "-" " " | title }}"
+date: {{ .Date }}
+---
+
diff --git a/users/fcuny/notes/config.toml b/users/fcuny/notes/config.toml
new file mode 100644
index 0000000..4f335a9
--- /dev/null
+++ b/users/fcuny/notes/config.toml
@@ -0,0 +1,41 @@
+baseURL = "https://notes.fcuny.net/"
+languageCode = "en-us"
+title = "Franck's notes"
+publishDir = "docs"
+enableGitInfo = true
+
+[params]
+  homeText = "A collection of notes"
+  mainSections = ['notes']
+
+[author]
+  name = "Franck Cuny"
+  email = "franck@fcuny.net"
+
+[taxonomies]
+  tag = "tags"
+
+[permalinks]
+  notes = "/notes/:slug/"
+  tags = "/tags/:slug/"
+
+[markup]
+  [markup.tableOfContents]
+    startLevel = 1
+    endLevel = 3
+    ordered = true
+  [markup.highlight]
+    anchorLineNos = false
+    codeFences = false
+    guessSyntax = false
+    hl_Lines = ""
+    lineAnchors = ""
+    lineNoStart = 1
+    lineNos = false
+    lineNumbersInTable = false
+    noClasses = true
+    style = "emacs"
+    tabWidth = 4
+
+[outputs]
+  home = [ "HTML" ]
diff --git a/users/fcuny/notes/content/notes/containerd-to-firecracker.org b/users/fcuny/notes/content/notes/containerd-to-firecracker.org
new file mode 100644
index 0000000..554771d
--- /dev/null
+++ b/users/fcuny/notes/content/notes/containerd-to-firecracker.org
@@ -0,0 +1,568 @@
+#+TITLE: containerd to firecracker
+#+DATE: <2021-05-15 Sat>
+#+TAGS[]: linux firecracker containerd go
+#+toc: t
+
+fly.io had an [[https://fly.io/blog/docker-without-docker/][interesting article]] about how they use docker images to create VMs for =firecracker=.
+
+They describe the process as follow:
+
+1. Pull a container from a registry
+2. Create a loop device to store the container's filesystem on
+3. Unpack the container into the mounted loop device
+4. Create a second block device and inject init, kernel, configuration and other stuff
+5. Attach persistent volumes (if any)
+6. Create a TAP device and configure it
+7. Hand it off to Firecracker and boot that thing
+
+That's pretty detailed, and I'm curious how difficult it is to implement this. I've been meaning to look into Firecracker for a while and into containers'd API, so this is a perfect opportunity to get started. The code is available [[https://git.fcuny.net/fcuny/containerd-to-vm][here]].
+
+* #1 Pull a container from a registry with =containerd=
+=containerd= has a pretty [[https://pkg.go.dev/github.com/containerd/containerd][detailed documentation]]. From the main page we can see the following example to create a client.
+#+begin_src go
+import (
+  "github.com/containerd/containerd"
+  "github.com/containerd/containerd/cio"
+)
+
+
+func main() {
+	client, err := containerd.New("/run/containerd/containerd.sock")
+	defer client.Close()
+}
+#+end_src
+
+And pulling an image is also pretty straightforward:
+#+begin_src go
+image, err := client.Pull(context, "docker.io/library/redis:latest")
+#+end_src
+
+The =Pull= method returns an [[https://pkg.go.dev/github.com/containerd/containerd@v1.4.4/images#Image][=Image=]] and there's a few methods associated with it.
+
+As =containerd= has namespaces, it's possible to specify the namespace we want to use when working with the API:
+#+begin_src go
+ctx := namespaces.WithNamespace(context.Background(), "c2vm")
+image, err := client.Pull(ctx, "docker.io/library/redis:latest")
+#+end_src
+
+The image will now be stored in the =c2vm= namespace. We can verify this with:
+#+begin_src sh
+; sudo ctr -n c2vm images ls -q
+docker.io/library/redis:latest
+#+end_src
+
+* #2 Create a loop device to store the container's filesystem on
+This is going to be pretty straightforward. To create a loop device we need to:
+1. pre-allocate space to a file
+2. convert that file to some format
+3. mount it to some destination
+
+There's two commons ways to pre-allocate space to a file: =dd= and =fallocate= (there's likely way more ways to do this). I'll go with =fallocate= for this example.
+
+First, to be safe, we create a temporary file, and use =renameio= to handle the renaming (I recommend reading the doc of the module).
+
+#+begin_src go
+f, err := renameio.TempFile("", rawFile)
+if err != nil {
+	return err
+}
+defer f.Cleanup()
+#+end_src
+
+Now to do the pre-allocation (we're making an assumption here that 2GB is enough, we can likely check what's the size of the container before doing this):
+#+begin_src go
+command := exec.Command("fallocate", "-l", "2G", f.Name())
+if err := command.Run(); err != nil {
+	return fmt.Errorf("fallocate error: %s", err)
+}
+#+end_src
+
+We can now convert that file to ext4:
+#+begin_src go
+command = exec.Command("mkfs.ext4", "-F", f.Name())
+if err := command.Run(); err != nil {
+	return fmt.Errorf("mkfs.ext4 error: %s", err)
+}
+#+end_src
+
+Now we can rename safely the temporary file to the proper file we want:
+#+begin_src go
+f.CloseAtomicallyReplace()
+#+end_src
+
+And to mount that file
+#+begin_src go
+command = exec.Command("mount", "-o", "loop", rawFile, mntDir)
+if err := command.Run(); err != nil {
+	return fmt.Errorf("mount error: %s", err)
+}
+#+end_src
+* #3 Unpack the container into the mounted loop device
+Extracting the container using =containerd= is pretty simple. Here's the function that I use:
+#+begin_src go
+func extract(ctx context.Context, client *containerd.Client, image containerd.Image, mntDir string) error {
+	manifest, err := images.Manifest(ctx, client.ContentStore(), image.Target(), platform)
+	if err != nil {
+		log.Fatalf("failed to get the manifest: %v\n", err)
+	}
+
+	for _, desc := range manifest.Layers {
+		log.Printf("extracting layer %s\n", desc.Digest.String())
+		layer, err := client.ContentStore().ReaderAt(ctx, desc)
+		if err != nil {
+			return err
+		}
+		if err := archive.Untar(content.NewReader(layer), mntDir, &archive.TarOptions{NoLchown: true}); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+#+end_src
+
+Calling =images.Manifest= returns the [[https://github.com/opencontainers/image-spec/blob/master/manifest.md][manifest]] from the image. What we care here are the list of layers. Here I'm making a number of assumptions regarding their type (we should be checking the media type first). We read the layers and extract them to the mounted path.
+* #4 Create a second block device and inject other stuff
+Here I'm going to deviate a bit. I will not create a second loop device, and I will not inject a kernel. In their article, they provided a link to a snapshot of their =init= process (https://github.com/superfly/init-snapshot). In order to keep this simple, our init is going to be a shell script composed of the content of the entry point of the container. We're also going to add a few extra files to container (=/etc/hosts= and =/etc/resolv.conf=).
+
+Finally, since we've pre-allocated 2GB for that container, and we likely don't need that much, we're also going to resize the image.
+** Add init
+Let's refer to the [[https://github.com/opencontainers/image-spec/blob/master/config.md][specification for the config]]. The elements that are of interest to me are:
+- =Env=, which is array of strings. They contain the environment variables that likely we need to run the program
+- =Cmd=, which is also an array of strings. If there's no entry point provided, this is what is used.
+
+At this point, for this experiment, I'm going to ignore exposed ports, working directory, and the user.
+
+First we need to read the config from the container. This is easily done:
+#+begin_src go
+config, err := images.Config(ctx, client.ContentStore(), image.Target(), platform)
+if err != nil {
+	return err
+}
+#+end_src
+
+This needs to be read and decoded:
+#+begin_src go
+configBlob, err := content.ReadBlob(ctx, client.ContentStore(), config)
+var imageSpec ocispec.Image
+json.Unmarshal(configBlob, &imageSpec)
+#+end_src
+
+=init= is the first process started by Linux during boot. On a regular Linux desktop you likely have a symbolic link from =/usr/bin/init= to =/usr/lib/systemd/systemd=, since most distributions have switched to =systemd=. For my use case however, I want to run a single process, and I want it to be the one from the container. For this we can create a simple shell script inside the container (the location does not matter for now) with the environment variables and the command.
+
+Naively, this can be done like this:
+#+begin_src go
+initPath := filepath.Join(mntDir, "init.sh")
+f, err := renameio.TempFile("", initPath)
+if err != nil {
+	return err
+}
+defer f.Cleanup()
+
+writer := bufio.NewWriter(f)
+fmt.Fprintf(writer, "#!/bin/sh\n")
+for _, env := range initEnvs {
+	fmt.Fprintf(writer, "export %s\n", env)
+}
+fmt.Fprintf(writer, "%s\n", initCmd)
+writer.Flush()
+
+f.CloseAtomicallyReplace()
+
+mode := int(0755)
+os.Chmod(initPath, os.FileMode(mode))
+#+end_src
+
+We're once again creating a  temporary file with =renamio=, and we're writing our shell scripts, one line at a time. We only need to make sure this executable.
+** extra files
+Once we have our init file, I also want to add a few extra files: =/etc/hosts= and =/etc/resolv.conf=. This files are not always present, since they can be injected by other systems. I also want to make sure that DNS resolutions are done using my own DNS server.
+** resize the image
+We've pre-allocated 2GB for the image, and it's likely we don't need as much space. We can do this by running =e2fsck= and =resize2fs= once we're done manipulating the image.
+
+Within a function, we can do the following:
+#+begin_src go
+command := exec.Command("/usr/bin/e2fsck", "-p", "-f", rawFile)
+if err := command.Run(); err != nil {
+	return fmt.Errorf("e2fsck error: %s", err)
+}
+
+command = exec.Command("resize2fs", "-M", rawFile)
+if err := command.Run(); err != nil {
+	return fmt.Errorf("resize2fs error: %s", err)
+}
+#+end_src
+
+I'm using =docker.io/library/redis:latest= for my test, and I end up with the following size for the image:
+#+begin_src bash
+-rw------- 1 root root 216M Apr 22 14:50 /tmp/fcuny.img
+#+end_src
+** Kernel
+We're going to need a kernel to run that VM. In my case I've decided to go with version 5.8, and build a custom kernel. If you are not familiar with the process, the firecracker team has [[https://github.com/firecracker-microvm/firecracker/blob/main/docs/rootfs-and-kernel-setup.md#creating-a-kernel-image][documented how to do this]]. In my case all I had to do was:
+#+begin_src sh
+git clone https://github.com/torvalds/linux.git linux.git
+cd linux.git
+git checkout v5.8
+curl -o .config -s https://github.com/firecracker-microvm/firecracker/blob/main/resources/microvm-kernel-x86_64.config
+make menuconfig
+make vmlinux -j8
+#+end_src
+
+Note that they also have a pretty [[https://github.com/firecracker-microvm/firecracker/blob/main/docs/prod-host-setup.md][good documentation for production]].
+* #5 Attach persistent volumes (if any)
+I'm going to skip that step for now.
+* #6 Create a TAP device and configure it
+We're going to need a network for that VM (otherwise it might be a bit boring).
+There's a few solutions that we can take:
+1. create the TAP device
+2. delegate all that work to a [[https://github.com/containernetworking/cni][CNI]]
+
+I've decided to use the CNI approach [[https://github.com/firecracker-microvm/firecracker-go-sdk#cni][documented in the Go's SDK]]. For this to work we need to install the =tc-redirect-tap= CNI plugin (available at https://github.com/awslabs/tc-redirect-tap).
+
+Based on that documentation, I'll start with the following configuration in =etc/cni/conf.d/50-c2vm.conflist=:
+#+begin_src json
+{
+  "name": "c2vm",
+  "cniVersion": "0.4.0",
+  "plugins": [
+    {
+      "type": "bridge",
+      "bridge": "c2vm-br",
+      "isDefaultGateway": true,
+      "forceAddress": false,
+      "ipMasq": true,
+      "hairpinMode": true,
+      "mtu": 1500,
+      "ipam": {
+        "type": "host-local",
+        "subnet": "192.168.128.0/24",
+        "resolvConf": "/etc/resolv.conf"
+      }
+    },
+    {
+      "type": "firewall"
+    },
+    {
+      "type": "tc-redirect-tap"
+    }
+  ]
+}
+#+end_src
+* #7 Hand it off to Firecracker and boot that thing
+Now that we have all the components, we need to boot that VM. Since I've been working with Go so far, I'll also use the [[https://github.com/firecracker-microvm/firecracker-go-sdk][Go SDK]] to manage and start the VM.
+
+For this we need the firecracker binary, which we can [[https://github.com/firecracker-microvm/firecracker/releases][find on GitHub]].
+
+The first thing is to configure the list of devices. In our case we will have a single device, the boot drive that we've created in the previous step.
+#+begin_src go
+devices := make([]models.Drive, 1)
+devices[0] = models.Drive{
+	DriveID:      firecracker.String("1"),
+	PathOnHost:   &rawImage,
+	IsRootDevice: firecracker.Bool(true),
+	IsReadOnly:   firecracker.Bool(false),
+}
+#+end_src
+
+The next step is to configure the VM:
+#+begin_src go
+fcCfg := firecracker.Config{
+	LogLevel:        "debug",
+	SocketPath:      firecrackerSock,
+	KernelImagePath: linuxKernel,
+	KernelArgs:      "console=ttyS0 reboot=k panic=1 acpi=off pci=off i8042.noaux i8042.nomux i8042.nopnp i8042.dumbkbd init=/init.sh random.trust_cpu=on",
+	Drives:          devices,
+	MachineCfg: models.MachineConfiguration{
+		VcpuCount:   firecracker.Int64(1),
+		CPUTemplate: models.CPUTemplate("C3"),
+		HtEnabled:   firecracker.Bool(true),
+		MemSizeMib:  firecracker.Int64(512),
+	},
+	NetworkInterfaces: []firecracker.NetworkInterface{
+		{
+			CNIConfiguration: &firecracker.CNIConfiguration{
+				NetworkName: "c2vm",
+				IfName:      "eth0",
+			},
+		},
+	},
+}
+#+end_src
+
+Finally we can create the command to start and run the VM:
+#+begin_src go
+command := firecracker.VMCommandBuilder{}.
+	WithBin(firecrackerBinary).
+	WithSocketPath(fcCfg.SocketPath).
+	WithStdin(os.Stdin).
+	WithStdout(os.Stdout).
+	WithStderr(os.Stderr).
+	Build(ctx)
+machineOpts = append(machineOpts, firecracker.WithProcessRunner(command))
+m, err := firecracker.NewMachine(vmmCtx, fcCfg, machineOpts...)
+if err != nil {
+	panic(err)
+}
+
+if err := m.Start(vmmCtx); err != nil {
+	panic(err)
+}
+defer m.StopVMM()
+
+if err := m.Wait(vmmCtx); err != nil {
+	panic(err)
+}
+#+end_src
+
+The end result:
+#+begin_src
+; sudo ./c2vm -container docker.io/library/redis:latest -firecracker-binary ./hack/firecracker/firecracker-v0.24.3-x86_64 -linux-kernel ./hack/linux/my-linux.bin -out /tmp/redis.img
+2021/05/15 14:12:59 pulled docker.io/library/redis:latest (38690247 bytes)
+2021/05/15 14:13:00 mounted /tmp/redis.img on /tmp/c2vm026771514
+2021/05/15 14:13:00 extracting layer sha256:69692152171afee1fd341febc390747cfca2ff302f2881d8b394e786af605696
+2021/05/15 14:13:00 extracting layer sha256:a4a46f2fd7e06fab84b4e78eb2d1b6d007351017f9b18dbeeef1a9e7cf194e00
+2021/05/15 14:13:00 extracting layer sha256:bcdf6fddc3bdaab696860eb0f4846895c53a3192c9d7bf8d2275770ea8073532
+2021/05/15 14:13:01 extracting layer sha256:b7e9b50900cc06838c44e0fc5cbebe5c0b3e7f70c02f32dd754e1aa6326ed566
+2021/05/15 14:13:01 extracting layer sha256:5f3030c50d85a9d2f70adb610b19b63290c6227c825639b227ddc586f86d1c76
+2021/05/15 14:13:01 extracting layer sha256:63dae8e0776cdbd63909fbd9c047c1615a01cb21b73efa87ae2feed680d3ffa1
+2021/05/15 14:13:01 init script created
+2021/05/15 14:13:01 umount /tmp/c2vm026771514
+INFO[0003] Called startVMM(), setting up a VMM on firecracker.sock
+INFO[0003] VMM logging disabled.
+INFO[0003] VMM metrics disabled.
+INFO[0003] refreshMachineConfiguration: [GET /machine-config][200] getMachineConfigurationOK  &{CPUTemplate:C3 HtEnabled:0xc0004e6753 MemSizeMib:0xc0004e6748 VcpuCount:0xc0004e6740}
+INFO[0003] PutGuestBootSource: [PUT /boot-source][204] putGuestBootSourceNoContent
+INFO[0003] Attaching drive /tmp/redis.img, slot 1, root true.
+INFO[0003] Attached drive /tmp/redis.img: [PUT /drives/{drive_id}][204] putGuestDriveByIdNoContent
+INFO[0003] Attaching NIC tap0 (hwaddr 9e:72:c7:04:6b:80) at index 1
+INFO[0003] startInstance successful: [PUT /actions][204] createSyncActionNoContent
+[    0.000000] Linux version 5.8.0 (fcuny@nas) (gcc (Debian 8.3.0-6) 8.3.0, GNU ld (GNU Binutils for Debian) 2.31.1) #1 SMP Mon Apr 12 20:07:40 PDT 2021
+[    0.000000] Command line: i8042.dumbkbd ip=192.168.128.9::192.168.128.1:255.255.255.0:::off::: console=ttyS0 reboot=k panic=1 acpi=off pci=off i8042.noaux i8042.nomux i8042.nopnp init=/init.sh random.trust_cpu=on root=/dev/vda rw virtio_mmio.device=4K@0xd0000000:5 virtio_mmio.device=4K@0xd0001000:6
+[    0.000000] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point registers'
+[    0.000000] x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers'
+[    0.000000] x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers'
+[    0.000000] x86/fpu: xstate_offset[2]:  576, xstate_sizes[2]:  256
+[    0.000000] x86/fpu: Enabled xstate features 0x7, context size is 832 bytes, using 'standard' format.
+[    0.000000] BIOS-provided physical RAM map:
+[    0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
+[    0.000000] BIOS-e820: [mem 0x0000000000100000-0x000000001fffffff] usable
+[    0.000000] NX (Execute Disable) protection: active
+[    0.000000] DMI not present or invalid.
+[    0.000000] Hypervisor detected: KVM
+[    0.000000] kvm-clock: Using msrs 4b564d01 and 4b564d00
+[    0.000000] kvm-clock: cpu 0, msr 2401001, primary cpu clock
+[    0.000000] kvm-clock: using sched offset of 11918596 cycles
+[    0.000005] clocksource: kvm-clock: mask: 0xffffffffffffffff max_cycles: 0x1cd42e4dffb, max_idle_ns: 881590591483 ns
+[    0.000011] tsc: Detected 1190.400 MHz processor
+[    0.000108] last_pfn = 0x20000 max_arch_pfn = 0x400000000
+[    0.000151] Disabled
+[    0.000156] x86/PAT: MTRRs disabled, skipping PAT initialization too.
+[    0.000166] CPU MTRRs all blank - virtualized system.
+[    0.000170] x86/PAT: Configuration [0-7]: WB  WT  UC- UC  WB  WT  UC- UC
+[    0.000201] found SMP MP-table at [mem 0x0009fc00-0x0009fc0f]
+[    0.000257] check: Scanning 1 areas for low memory corruption
+[    0.000364] No NUMA configuration found
+[    0.000365] Faking a node at [mem 0x0000000000000000-0x000000001fffffff]
+[    0.000370] NODE_DATA(0) allocated [mem 0x1ffde000-0x1fffffff]
+[    0.000490] Zone ranges:
+[    0.000493]   DMA      [mem 0x0000000000001000-0x0000000000ffffff]
+[    0.000494]   DMA32    [mem 0x0000000001000000-0x000000001fffffff]
+[    0.000495]   Normal   empty
+[    0.000497] Movable zone start for each node
+[    0.000500] Early memory node ranges
+[    0.000501]   node   0: [mem 0x0000000000001000-0x000000000009efff]
+[    0.000502]   node   0: [mem 0x0000000000100000-0x000000001fffffff]
+[    0.000510] Zeroed struct page in unavailable ranges: 98 pages
+[    0.000511] Initmem setup node 0 [mem 0x0000000000001000-0x000000001fffffff]
+[    0.004990] Intel MultiProcessor Specification v1.4
+[    0.004995] MPTABLE: OEM ID: FC
+[    0.004995] MPTABLE: Product ID: 000000000000
+[    0.004996] MPTABLE: APIC at: 0xFEE00000
+[    0.005007] Processor #0 (Bootup-CPU)
+[    0.005039] IOAPIC[0]: apic_id 2, version 17, address 0xfec00000, GSI 0-23
+[    0.005041] Processors: 1
+[    0.005042] TSC deadline timer available
+[    0.005044] smpboot: Allowing 1 CPUs, 0 hotplug CPUs
+[    0.005060] KVM setup pv remote TLB flush
+[    0.005072] KVM setup pv sched yield
+[    0.005078] PM: hibernation: Registered nosave memory: [mem 0x00000000-0x00000fff]
+[    0.005079] PM: hibernation: Registered nosave memory: [mem 0x0009f000-0x000fffff]
+[    0.005081] [mem 0x20000000-0xffffffff] available for PCI devices
+[    0.005082] Booting paravirtualized kernel on KVM
+[    0.005084] clocksource: refined-jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 7645519600211568 ns
+[    0.005087] setup_percpu: NR_CPUS:128 nr_cpumask_bits:128 nr_cpu_ids:1 nr_node_ids:1
+[    0.006381] percpu: Embedded 44 pages/cpu s143360 r8192 d28672 u2097152
+[    0.006404] KVM setup async PF for cpu 0
+[    0.006410] kvm-stealtime: cpu 0, msr 1f422080
+[    0.006420] Built 1 zonelists, mobility grouping on.  Total pages: 128905
+[    0.006420] Policy zone: DMA32
+[    0.006422] Kernel command line: i8042.dumbkbd ip=192.168.128.9::192.168.128.1:255.255.255.0:::off::: console=ttyS0 reboot=k panic=1 acpi=off pci=off i8042.noaux i8042.nomux i8042.nopnp init=/init.sh random.trust_cpu=on root=/dev/vda rw virtio_mmio.device=4K@0xd0000000:5 virtio_mmio.device=4K@0xd0001000:6
+[    0.006858] Dentry cache hash table entries: 65536 (order: 7, 524288 bytes, linear)
+[    0.007003] Inode-cache hash table entries: 32768 (order: 6, 262144 bytes, linear)
+[    0.007047] mem auto-init: stack:off, heap alloc:off, heap free:off
+[    0.007947] Memory: 491940K/523896K available (10243K kernel code, 629K rwdata, 1860K rodata, 1408K init, 6048K bss, 31956K reserved, 0K cma-reserved)
+[    0.007980] random: get_random_u64 called from __kmem_cache_create+0x3d/0x540 with crng_init=0
+[    0.008053] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
+[    0.008146] rcu: Hierarchical RCU implementation.
+[    0.008147] rcu:     RCU restricting CPUs from NR_CPUS=128 to nr_cpu_ids=1.
+[    0.008151] rcu: RCU calculated value of scheduler-enlistment delay is 25 jiffies.
+[    0.008152] rcu: Adjusting geometry for rcu_fanout_leaf=16, nr_cpu_ids=1
+[    0.008170] NR_IRQS: 4352, nr_irqs: 48, preallocated irqs: 16
+[    0.008373] random: crng done (trusting CPU's manufacturer)
+[    0.008430] Console: colour dummy device 80x25
+[    0.052276] printk: console [ttyS0] enabled
+[    0.052685] APIC: Switch to symmetric I/O mode setup
+[    0.053288] x2apic enabled
+[    0.053705] Switched APIC routing to physical x2apic.
+[    0.054213] KVM setup pv IPIs
+[    0.055559] clocksource: tsc-early: mask: 0xffffffffffffffff max_cycles: 0x1128af0325d, max_idle_ns: 440795261011 ns
+[    0.056516] Calibrating delay loop (skipped) preset value.. 2380.80 BogoMIPS (lpj=4761600)
+[    0.057259] pid_max: default: 32768 minimum: 301
+[    0.057726] LSM: Security Framework initializing
+[    0.058176] SELinux:  Initializing.
+[    0.058556] Mount-cache hash table entries: 1024 (order: 1, 8192 bytes, linear)
+[    0.059221] Mountpoint-cache hash table entries: 1024 (order: 1, 8192 bytes, linear)
+[    0.060382] x86/cpu: User Mode Instruction Prevention (UMIP) activated
+[    0.060510] Last level iTLB entries: 4KB 0, 2MB 0, 4MB 0
+[    0.060510] Last level dTLB entries: 4KB 0, 2MB 0, 4MB 0, 1GB 0
+[    0.060510] Spectre V1 : Mitigation: usercopy/swapgs barriers and __user pointer sanitization
+[    0.060510] Spectre V2 : Mitigation: Enhanced IBRS
+[    0.060510] Spectre V2 : Spectre v2 / SpectreRSB mitigation: Filling RSB on context switch
+[    0.060510] Spectre V2 : mitigation: Enabling conditional Indirect Branch Prediction Barrier
+[    0.060510] Speculative Store Bypass: Mitigation: Speculative Store Bypass disabled via prctl and seccomp
+[    0.060510] Freeing SMP alternatives memory: 32K
+[    0.060510] smpboot: CPU0: Intel(R) Xeon(R) Processor @ 1.20GHz (family: 0x6, model: 0x3e, stepping: 0x4)
+[    0.060510] Performance Events: unsupported p6 CPU model 62 no PMU driver, software events only.
+[    0.060510] rcu: Hierarchical SRCU implementation.
+[    0.060510] smp: Bringing up secondary CPUs ...
+[    0.060510] smp: Brought up 1 node, 1 CPU
+[    0.060510] smpboot: Max logical packages: 1
+[    0.060523] smpboot: Total of 1 processors activated (2380.80 BogoMIPS)
+[    0.061338] devtmpfs: initialized
+[    0.061710] x86/mm: Memory block size: 128MB
+[    0.062341] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 7645041785100000 ns
+[    0.063245] futex hash table entries: 256 (order: 2, 16384 bytes, linear)
+[    0.063946] thermal_sys: Registered thermal governor 'fair_share'
+[    0.063946] thermal_sys: Registered thermal governor 'step_wise'
+[    0.064522] thermal_sys: Registered thermal governor 'user_space'
+[    0.065313] NET: Registered protocol family 16
+[    0.066398] DMA: preallocated 128 KiB GFP_KERNEL pool for atomic allocations
+[    0.067057] DMA: preallocated 128 KiB GFP_KERNEL|GFP_DMA pool for atomic allocations
+[    0.067778] DMA: preallocated 128 KiB GFP_KERNEL|GFP_DMA32 pool for atomic allocations
+[    0.068506] audit: initializing netlink subsys (disabled)
+[    0.068708] cpuidle: using governor ladder
+[    0.069097] cpuidle: using governor menu
+[    0.070636] audit: type=2000 audit(1621113181.800:1): state=initialized audit_enabled=0 res=1
+[    0.076346] HugeTLB registered 2.00 MiB page size, pre-allocated 0 pages
+[    0.077007] ACPI: Interpreter disabled.
+[    0.077445] SCSI subsystem initialized
+[    0.077812] pps_core: LinuxPPS API ver. 1 registered
+[    0.078277] pps_core: Software ver. 5.3.6 - Copyright 2005-2007 Rodolfo Giometti <giometti@linux.it>
+[    0.079206] PTP clock support registered
+[    0.079741] NetLabel: Initializing
+[    0.080111] NetLabel:  domain hash size = 128
+[    0.080529] NetLabel:  protocols = UNLABELED CIPSOv4 CALIPSO
+[    0.081113] NetLabel:  unlabeled traffic allowed by default
+[    0.082072] clocksource: Switched to clocksource kvm-clock
+[    0.082715] VFS: Disk quotas dquot_6.6.0
+[    0.083123] VFS: Dquot-cache hash table entries: 512 (order 0, 4096 bytes)
+[    0.083855] pnp: PnP ACPI: disabled
+[    0.084510] NET: Registered protocol family 2
+[    0.084718] tcp_listen_portaddr_hash hash table entries: 256 (order: 0, 4096 bytes, linear)
+[    0.085602] TCP established hash table entries: 4096 (order: 3, 32768 bytes, linear)
+[    0.086365] TCP bind hash table entries: 4096 (order: 4, 65536 bytes, linear)
+[    0.087025] TCP: Hash tables configured (established 4096 bind 4096)
+[    0.087749] UDP hash table entries: 256 (order: 1, 8192 bytes, linear)
+[    0.088481] UDP-Lite hash table entries: 256 (order: 1, 8192 bytes, linear)
+[    0.089261] NET: Registered protocol family 1
+[    0.090395] virtio-mmio: Registering device virtio-mmio.0 at 0xd0000000-0xd0000fff, IRQ 5.
+[    0.091388] virtio-mmio: Registering device virtio-mmio.1 at 0xd0001000-0xd0001fff, IRQ 6.
+[    0.092222] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: 0x1128af0325d, max_idle_ns: 440795261011 ns
+[    0.093322] clocksource: Switched to clocksource tsc
+[    0.093824] platform rtc_cmos: registered platform RTC device (no PNP device found)
+[    0.094618] check: Scanning for low memory corruption every 60 seconds
+[    0.095394] Initialise system trusted keyrings
+[    0.095836] Key type blacklist registered
+[    0.096427] workingset: timestamp_bits=36 max_order=17 bucket_order=0
+[    0.097849] squashfs: version 4.0 (2009/01/31) Phillip Lougher
+[    0.107488] Key type asymmetric registered
+[    0.107905] Asymmetric key parser 'x509' registered
+[    0.108409] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 252)
+[    0.109435] Serial: 8250/16550 driver, 1 ports, IRQ sharing disabled
+[    0.110116] serial8250: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A
+[    0.111877] loop: module loaded
+[    0.112426] virtio_blk virtio0: [vda] 441152 512-byte logical blocks (226 MB/215 MiB)
+[    0.113229] vda: detected capacity change from 0 to 225869824
+[    0.114143] Loading iSCSI transport class v2.0-870.
+[    0.114753] iscsi: registered transport (tcp)
+[    0.115162] tun: Universal TUN/TAP device driver, 1.6
+[    0.115955] i8042: PNP detection disabled
+[    0.116498] serio: i8042 KBD port at 0x60,0x64 irq 1
+[    0.117089] input: AT Raw Set 2 keyboard as /devices/platform/i8042/serio0/input/input0
+[    0.117932] intel_pstate: CPU model not supported
+[    0.118448] hid: raw HID events driver (C) Jiri Kosina
+[    0.119090] Initializing XFRM netlink socket
+[    0.119555] NET: Registered protocol family 10
+[    0.120285] Segment Routing with IPv6
+[    0.120812] NET: Registered protocol family 17
+[    0.121350] Bridge firewalling registered
+[    0.122026] NET: Registered protocol family 40
+[    0.122515] IPI shorthand broadcast: enabled
+[    0.122961] sched_clock: Marking stable (72512224, 48198862)->(137683636, -16972550)
+[    0.123796] registered taskstats version 1
+[    0.124203] Loading compiled-in X.509 certificates
+[    0.125355] Loaded X.509 cert 'Build time autogenerated kernel key: 6203e6adc37b712d3b220a26b38f3d31311d5966'
+[    0.126355] Key type ._fscrypt registered
+[    0.126736] Key type .fscrypt registered
+[    0.127109] Key type fscrypt-provisioning registered
+[    0.127657] Key type encrypted registered
+[    0.144629] IP-Config: Complete:
+[    0.144968]      device=eth0, hwaddr=9e:72:c7:04:6b:80, ipaddr=192.168.128.9, mask=255.255.255.0, gw=192.168.128.1
+[    0.146044]      host=192.168.128.9, domain=, nis-domain=(none)
+[    0.146604]      bootserver=255.255.255.255, rootserver=255.255.255.255, rootpath=
+[    0.148347] EXT4-fs (vda): mounted filesystem with ordered data mode. Opts: (null)
+[    0.149098] VFS: Mounted root (ext4 filesystem) on device 254:0.
+[    0.149761] devtmpfs: mounted
+[    0.150340] Freeing unused decrypted memory: 2040K
+[    0.151148] Freeing unused kernel image (initmem) memory: 1408K
+[    0.156621] Write protecting the kernel read-only data: 14336k
+[    0.158657] Freeing unused kernel image (text/rodata gap) memory: 2044K
+[    0.159490] Freeing unused kernel image (rodata/data gap) memory: 188K
+[    0.160150] Run /init.sh as init process
+462:C 15 May 2021 21:13:01.903 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
+462:C 15 May 2021 21:13:01.904 # Redis version=6.2.3, bits=64, commit=00000000, modified=0, pid=462, just started
+462:C 15 May 2021 21:13:01.905 # Warning: no config file specified, using the default config. In order to specify a config file use redis-server /path/to/redis.conf
+462:M 15 May 2021 21:13:01.907 * Increased maximum number of open files to 10032 (it was originally set to 1024).
+462:M 15 May 2021 21:13:01.909 * monotonic clock: POSIX clock_gettime
+                _._
+           _.-``__ ''-._
+      _.-``    `.  `_.  ''-._           Redis 6.2.3 (00000000/0) 64 bit
+  .-`` .-```.  ```\/    _.,_ ''-._
+ (    '      ,       .-`  | `,    )     Running in standalone mode
+ |`-._`-...-` __...-.``-._|'` _.-'|     Port: 6379
+ |    `-._   `._    /     _.-'    |     PID: 462
+  `-._    `-._  `-./  _.-'    _.-'
+ |`-._`-._    `-.__.-'    _.-'_.-'|
+ |    `-._`-._        _.-'_.-'    |           https://redis.io
+  `-._    `-._`-.__.-'_.-'    _.-'
+ |`-._`-._    `-.__.-'    _.-'_.-'|
+ |    `-._`-._        _.-'_.-'    |
+  `-._    `-._`-.__.-'_.-'    _.-'
+      `-._    `-.__.-'    _.-'
+          `-._        _.-'
+              `-.__.-'
+
+462:M 15 May 2021 21:13:01.922 # Server initialized
+462:M 15 May 2021 21:13:01.923 * Ready to accept connections
+#+end_src
+
+We can do a quick test with the following:
+#+begin_src sh
+; sudo docker run -it --rm redis redis-cli -h 192.168.128.9
+192.168.128.9:6379> get foo
+(nil)
+192.168.128.9:6379> set foo 1
+OK
+192.168.128.9:6379> get foo
+"1"
+192.168.128.9:6379>
+#+end_src
diff --git a/users/fcuny/notes/content/notes/making-sense-intel-amd-cpus.org b/users/fcuny/notes/content/notes/making-sense-intel-amd-cpus.org
new file mode 100644
index 0000000..60b433f
--- /dev/null
+++ b/users/fcuny/notes/content/notes/making-sense-intel-amd-cpus.org
@@ -0,0 +1,131 @@
+#+TITLE: Making sense of Intel and AMD CPUs naming
+#+DATE: <2021-12-29 Wed>
+#+TAGS[]: amd intel cpu
+#+toc: headlines 1
+
+* Intel
+** Core
+The line up for the core family is i3, i5, i7 and i9. As of December 2021, the current generation is Alder Lake (12th generation).
+
+The brand modifiers are:
+- *i3*: laptops/low-end desktop
+- *i5*: mainstream users
+- *i7*: high-end users
+- *i9*: enthusiast users
+
+How to read a SKU ? Let's use the [[https://ark.intel.com/content/www/us/en/ark/products/134594/intel-core-i712700k-processor-25m-cache-up-to-5-00-ghz.html][i7-12700K]] processor:
+- *i7*: high end users
+- *12*: 12th generation
+- *700*: SKU digits, usually assigned in the order the processors are developed
+- *K*: unlocked
+
+List of suffixes:
+| suffix | meaning                                |
+|--------+----------------------------------------|
+| G..    | integrated graphics                    |
+| E      | embedded                               |
+| F      | require discrete graphic card          |
+| H      | high performance for mobile            |
+| HK     | high performance for mobile / unlocked |
+| K      | unlocked                               |
+| S      | special edition                        |
+| T      | power optimized lifestyle              |
+| U      | mobile power efficient                 |
+| Y      | mobile low power                       |
+| X/XE   | unlocked, high end                     |
+
+#+begin_quote
+*Unlocked,* what does that means ?
+A processor with the *K* suffix is made with the an unlocked clock multiplier. When used with some specific chipset, it's possible to overclock the processor.
+#+end_quote
+*** Sockets/Chipsets
+For the Alder Lake generation, the supported socket is the [[https://en.wikipedia.org/wiki/LGA_1700][LGA_1700]].
+
+For now only supported chipset for Alder Lake are:
+| feature                     | [[https://ark.intel.com/content/www/us/en/ark/products/218833/intel-z690-chipset.html][z690]]     | [[https://www.intel.com/content/www/us/en/products/sku/218831/intel-h670-chipset/specifications.html][h670]]     | [[https://ark.intel.com/content/www/us/en/ark/products/218832/intel-b660-chipset.html][b660]]    | [[https://www.intel.com/content/www/us/en/products/sku/218829/intel-h610-chipset/specifications.html][h610]] |
+|-----------------------------+----------+----------+---------+------|
+| P and E cores over clocking | yes      | no       | no      | no   |
+| memory over clocking        | yes      | yes      | yes     | no   |
+| DMI 4 lanes                 | 8        | 8        | 4       | 4    |
+| chipset PCIe 4.0 lanes      | up to 12 | up to 12 | up to 6 | none |
+| chipset PCIe 3.0 lanes      | up to 16 | up to 12 | up to 8 | 8    |
+| SATA 3.0 ports              | up to 8  | up to 8  | 4       | 4    |
+
+*** Alder Lake (12th generation)
+| model      | p-cores | e-cores | GHz (base) | GHz (boosted) | TDP  |
+|------------+---------+---------+------------+---------------+------|
+| i9-12900K  | 8 (16)  |       8 | 3.2/2.4    | 5.1/3.9       | 241W |
+| i9-12900KF | 8 (16)  |       8 | 3.2/2.4    | 5.1/3.9       | 241W |
+| i7-12700K  | 8 (16)  |       4 | 3.6/2.7    | 4.9/3.8       | 190W |
+| i7-12700KF | 8 (16)  |       4 | 3.6/2.7    | 4.9/3.8       | 190W |
+| i5-12600K  | 6 (12)  |       4 | 3.7/2.8    | 4.9/3.6       | 150W |
+| i5-12600KF | 6 (12)  |       4 | 3.7/2.8    | 4.9/3.6       | 150W |
+
+- support DDR4 and DDR5 (up to DDR5-4800)
+- support PCIe 4.0 and 5.0 (16 PCIe 5.0 and 4 PCIe 4.0)
+
+The socket used is the [[https://en.wikipedia.org/wiki/LGA_1700][LGA 1700]].
+
+Alder lake is an hybrid architecture, featuring both P-cores (performance cores) and E-cores (efficient cores). P-cores are based on the [[https://en.wikipedia.org/wiki/Golden_Cove][Golden Cove]] architecture, while the E-cores are based on the [[https://en.wikipedia.org/wiki/Gracemont_(microarchitecture)][Gracemont]] architecture.
+
+This is a [[https://www.anandtech.com/show/16881/a-deep-dive-into-intels-alder-lake-microarchitectures/2][good article]] to read about this model. Inside the processor there's a microcontroller that monitors what each thread is doing. This can be used by the OS scheduler to hint on which core a thread should be scheduled on (between performance or efficiency).
+
+As of December 2021 this is not yet properly supported by the Linux kernel.
+** Xeon
+Xeon is the brand of Intel processor designed for non-consumer servers and workstations.
+The most recent generations are:
+- Skylake (2017)
+- Cascade lake (2019)
+- Cooper lake (2020)
+
+The following brand identifiers are used:
+- platinium
+- gold
+- silver
+- bronze
+* AMD
+** Ryzen
+There are multiple generation for this brand of processors. They are based on the [[https://en.wikipedia.org/wiki/Zen_(microarchitecture)][zen micro architecture]]. The current (as of December 2021) generation is Ryzen 5000.
+
+The brand modifiers are:
+- ryzen 3: entry level
+- ryzen 5: mainstream
+- ryzen 9: high end performance
+- ryzen 9:enthusiast
+
+List of suffixes:
+| suffix | meaning                                    |
+|--------+--------------------------------------------|
+| X      | high performance                           |
+| G      | integrated graphics                        |
+| T      | power optimized lifecycle                  |
+| S      | low power desktop with integrated graphics |
+| H      | high performance mobile                    |
+| U      | standard mobile                            |
+| M      | low power mobile                           |
+
+** EPYC
+EPYC is the AMD brand of processors for the server market, based on the zen architecture. They use the [[https://en.wikipedia.org/wiki/Socket_SP3][SP3]] socket. The EPYC processor is chipset free.
+** Threadripper
+The threadripper is for high performance desktop. It uses the [[https://en.wikipedia.org/wiki/Socket_TR4][TR4]] socket. At the moment there's only one chipset that supports this process, the [[https://en.wikipedia.org/wiki/List_of_AMD_chipsets#TR4_chipsets][X399]].
+
+The threadripper based on zen3 architecture is not yet released, but it's expected to hit the market in the first half of Q1 2022.
+** Sockets/Chipsets
+The majority of these processors use the [[https://en.wikipedia.org/wiki/Socket_AM4][AM4 socket]]. The threadripper line uses different sockets.
+
+There are multiple [[https://en.wikipedia.org/wiki/Socket_AM4#Chipsets][chipset]] for the AM4 socket. The more advanced ones are the B550 and the X570.
+
+The threadripper processors use the TR4, sTRX4 and sWRX8 sockets.
+** Zen 3
+Zen 3 was released in November 2020.
+| model         | cores   | GHz (base) | GHz (boosted) | PCIe lanes | TDP  |
+|---------------+---------+------------+---------------+------------+------|
+| ryzen 5 5600x | 6 (12)  |        3.7 |           4.6 |         24 | 65W  |
+| ryzen 7 5800  | 8 (16)  |        3.4 |           4.6 |         24 | 65W  |
+| ryzen 7 5800x | 8 (16)  |        3.8 |           4.7 |         24 | 105W |
+| ryzen 9 5900  | 12 (24) |        3.0 |           4.7 |         24 | 65W  |
+| ryzen 9 5900x | 12 (24) |        3.7 |           4.8 |         24 | 105W |
+| ryzen 9 5950x | 16 (32) |        3.4 |           4.9 |         24 | 105W |
+
+- support PCIe 3.0 and PCIe 4.0 (except for the G series)
+- only support DDR4 (up to DDR4-3200)
diff --git a/users/fcuny/notes/content/notes/stuff-about-pcie.org b/users/fcuny/notes/content/notes/stuff-about-pcie.org
new file mode 100644
index 0000000..eeb0b16
--- /dev/null
+++ b/users/fcuny/notes/content/notes/stuff-about-pcie.org
@@ -0,0 +1,199 @@
+#+TITLE: Stuff about PCIe
+#+DATE: <2022-01-03 Mon>
+#+TAGS[]: linux hardware
+#+toc: t
+
+* Speed
+The most common versions are 3 and 4, while 5 is starting to be available with newer Intel processors.
+
+| ver | encoding  | transfer rate | x1         | x2          | x4         | x8         | x16         |
+|-----+-----------+---------------+------------+-------------+------------+------------+-------------|
+|   1 | 8b/10b    | 2.5GT/s       | 250MB/s    | 500MB/s     | 1GB/s      | 2GB/s      | 4GB/s       |
+|   2 | 8b/10b    | 5.0GT/s       | 500MB/s    | 1GB/s       | 2GB/s      | 4GB/s      | 8GB/s       |
+|   3 | 128b/130b | 8.0GT/s       | 984.6 MB/s | 1.969 GB/s  | 3.94 GB/s  | 7.88 GB/s  | 15.75 GB/s  |
+|   4 | 128b/130b | 16.0GT/s      | 1969 MB/s  | 3.938 GB/s  | 7.88 GB/s  | 15.75 GB/s | 31.51 GB/s  |
+|   5 | 128b/130b | 32.0GT/s      | 3938 MB/s  | 7.877 GB/s  | 15.75 GB/s | 31.51 GB/s | 63.02 GB/s  |
+|   6 | 128b/130  | 64.0 GT/s     | 7877 MB/s  | 15.754 GB/s | 31.51 GB/s | 63.02 GB/s | 126.03 GB/s |
+
+This is a [[https://community.mellanox.com/s/article/understanding-pcie-configuration-for-maximum-performance][useful]] link to understand the formula:
+#+begin_quote
+Maximum PCIe Bandwidth = *SPEED* * *WIDTH* * (1 - ENCODING) - 1Gb/s.
+#+end_quote
+
+We remove 1Gb/s for protocol overhead and error corrections. The main difference between the generations besides the supported speed is the encoding overhead of the packet. For generations 1 and 2, each packet sent on the PCIe has 20% PCIe headers overhead. This was improved in generation 3, where the overhead was reduced to 1.5% (2/130) - see [[https://en.wikipedia.org/wiki/8b/10b_encoding][8b/10b encoding]] and [[https://en.wikipedia.org/wiki/64b/66b_encoding][128b/130b encoding]].
+
+If we apply the formula, for a PCIe version 3 device we can expect 3.7GB/s of data transfer rate:
+#+begin_src
+8GT/s * 4 lanes * (1 - 2/130) - 1G = 32G * 0.985 - 1G = ~30Gb/s -> 3750MB/s
+#+end_src
+* Topology
+The easiest way to see the PCIe topology is with =lspci=:
+#+begin_src
+$ lspci -tv
+-[0000:00]-+-00.0  Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-0fh) Root Complex
+           +-01.0  Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-1fh) PCIe Dummy Host Bridge
+           +-01.1-[01]----00.0  OCZ Technology Group, Inc. RD400/400A SSD
+           +-01.3-[02-03]----00.0-[03]----00.0  ASPEED Technology, Inc. ASPEED Graphics Family
+           +-01.5-[04]--+-00.0  Intel Corporation I350 Gigabit Network Connection
+           |            +-00.1  Intel Corporation I350 Gigabit Network Connection
+           |            +-00.2  Intel Corporation I350 Gigabit Network Connection
+           |            \-00.3  Intel Corporation I350 Gigabit Network Connection
+           +-02.0  Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-1fh) PCIe Dummy Host Bridge
+           +-03.0  Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-1fh) PCIe Dummy Host Bridge
+           +-04.0  Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-1fh) PCIe Dummy Host Bridge
+           +-07.0  Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-1fh) PCIe Dummy Host Bridge
+           +-07.1-[05]--+-00.0  Advanced Micro Devices, Inc. [AMD] Zeppelin/Raven/Raven2 PCIe Dummy Function
+           |            +-00.2  Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-0fh) Platform Security Processor
+           |            \-00.3  Advanced Micro Devices, Inc. [AMD] Zeppelin USB 3.0 Host controller
+           +-08.0  Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-1fh) PCIe Dummy Host Bridge
+           +-08.1-[06]--+-00.0  Advanced Micro Devices, Inc. [AMD] Zeppelin/Renoir PCIe Dummy Function
+           |            +-00.1  Advanced Micro Devices, Inc. [AMD] Zeppelin Cryptographic Coprocessor NTBCCP
+           |            +-00.2  Advanced Micro Devices, Inc. [AMD] FCH SATA Controller [AHCI mode]
+           |            \-00.3  Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-0fh) HD Audio Controller
+           +-14.0  Advanced Micro Devices, Inc. [AMD] FCH SMBus Controller
+           +-14.3  Advanced Micro Devices, Inc. [AMD] FCH LPC Bridge
+           +-18.0  Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-0fh) Data Fabric: Device 18h; Function 0
+           +-18.1  Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-0fh) Data Fabric: Device 18h; Function 1
+           +-18.2  Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-0fh) Data Fabric: Device 18h; Function 2
+           +-18.3  Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-0fh) Data Fabric: Device 18h; Function 3
+           +-18.4  Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-0fh) Data Fabric: Device 18h; Function 4
+           +-18.5  Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-0fh) Data Fabric: Device 18h; Function 5
+           +-18.6  Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-0fh) Data Fabric: Device 18h; Function 6
+           \-18.7  Advanced Micro Devices, Inc. [AMD] Family 17h (Models 00h-0fh) Data Fabric: Device 18h; Function 7
+#+end_src
+* View a single device
+#+begin_src
+$ lspci -s 0000:01:00.0
+01:00.0 Non-Volatile memory controller: OCZ Technology Group, Inc. RD400/400A SSD (rev 01)
+#+end_src
+* Reading =lspci= output
+#+begin_src
+$ sudo lspci -vvv -s 0000:01:00.0
+01:00.0 Non-Volatile memory controller: OCZ Technology Group, Inc. RD400/400A SSD (rev 01) (prog-if 02 [NVM Express])
+	Subsystem: OCZ Technology Group, Inc. RD400/400A SSD
+	Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
+	Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
+	Latency: 0, Cache Line Size: 64 bytes
+	Interrupt: pin A routed to IRQ 41
+	NUMA node: 0
+	Region 0: Memory at ef800000 (64-bit, non-prefetchable) [size=16K]
+	Capabilities: [40] Power Management version 3
+		Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
+		Status: D0 NoSoftRst+ PME-Enable- DSel=0 DScale=0 PME-
+	Capabilities: [50] MSI: Enable- Count=1/8 Maskable- 64bit+
+		Address: 0000000000000000  Data: 0000
+	Capabilities: [70] Express (v2) Endpoint, MSI 00
+		DevCap:	MaxPayload 128 bytes, PhantFunc 0, Latency L0s unlimited, L1 unlimited
+			ExtTag+ AttnBtn- AttnInd- PwrInd- RBE+ FLReset+ SlotPowerLimit 0.000W
+		DevCtl:	CorrErr- NonFatalErr- FatalErr- UnsupReq-
+			RlxdOrd+ ExtTag+ PhantFunc- AuxPwr- NoSnoop- FLReset-
+			MaxPayload 128 bytes, MaxReadReq 512 bytes
+		DevSta:	CorrErr+ NonFatalErr- FatalErr- UnsupReq+ AuxPwr+ TransPend-
+		LnkCap:	Port #0, Speed 8GT/s, Width x4, ASPM L1, Exit Latency L1 <4us
+			ClockPM- Surprise- LLActRep- BwNot- ASPMOptComp+
+		LnkCtl:	ASPM L1 Enabled; RCB 64 bytes, Disabled- CommClk+
+			ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
+		LnkSta:	Speed 8GT/s (ok), Width x4 (ok)
+			TrErr- Train- SlotClk+ DLActive- BWMgmt- ABWMgmt-
+		DevCap2: Completion Timeout: Range ABCD, TimeoutDis+ NROPrPrP- LTR+
+			 10BitTagComp- 10BitTagReq- OBFF Not Supported, ExtFmt- EETLPPrefix-
+			 EmergencyPowerReduction Not Supported, EmergencyPowerReductionInit-
+			 FRS- TPHComp- ExtTPHComp-
+			 AtomicOpsCap: 32bit- 64bit- 128bitCAS-
+		DevCtl2: Completion Timeout: 50us to 50ms, TimeoutDis- LTR- OBFF Disabled,
+			 AtomicOpsCtl: ReqEn-
+		LnkCap2: Supported Link Speeds: 2.5-8GT/s, Crosslink- Retimer- 2Retimers- DRS-
+		LnkCtl2: Target Link Speed: 8GT/s, EnterCompliance- SpeedDis-
+			 Transmit Margin: Normal Operating Range, EnterModifiedCompliance- ComplianceSOS-
+			 Compliance De-emphasis: -6dB
+		LnkSta2: Current De-emphasis Level: -3.5dB, EqualizationComplete+ EqualizationPhase1+
+			 EqualizationPhase2+ EqualizationPhase3+ LinkEqualizationRequest-
+			 Retimer- 2Retimers- CrosslinkRes: unsupported
+	Capabilities: [b0] MSI-X: Enable+ Count=8 Masked-
+		Vector table: BAR=0 offset=00002000
+		PBA: BAR=0 offset=00003000
+	Capabilities: [100 v2] Advanced Error Reporting
+		UESta:	DLP- SDES- TLP- FCP- CmpltTO- CmpltAbrt- UnxCmplt- RxOF- MalfTLP- ECRC- UnsupReq+ ACSViol-
+		UEMsk:	DLP- SDES- TLP- FCP- CmpltTO- CmpltAbrt- UnxCmplt- RxOF- MalfTLP- ECRC- UnsupReq- ACSViol-
+		UESvrt:	DLP+ SDES+ TLP- FCP+ CmpltTO- CmpltAbrt- UnxCmplt- RxOF+ MalfTLP+ ECRC- UnsupReq- ACSViol-
+		CESta:	RxErr- BadTLP- BadDLLP- Rollover- Timeout- AdvNonFatalErr+
+		CEMsk:	RxErr- BadTLP- BadDLLP- Rollover- Timeout- AdvNonFatalErr-
+		AERCap:	First Error Pointer: 14, ECRCGenCap+ ECRCGenEn- ECRCChkCap+ ECRCChkEn-
+			MultHdrRecCap- MultHdrRecEn- TLPPfxPres- HdrLogCap-
+		HeaderLog: 05000001 0000010f 02000010 0f86d1a0
+	Capabilities: [178 v1] Secondary PCI Express
+		LnkCtl3: LnkEquIntrruptEn- PerformEqu-
+		LaneErrStat: 0
+	Capabilities: [198 v1] Latency Tolerance Reporting
+		Max snoop latency: 0ns
+		Max no snoop latency: 0ns
+	Capabilities: [1a0 v1] L1 PM Substates
+		L1SubCap: PCI-PM_L1.2+ PCI-PM_L1.1- ASPM_L1.2+ ASPM_L1.1- L1_PM_Substates+
+			  PortCommonModeRestoreTime=255us PortTPowerOnTime=400us
+		L1SubCtl1: PCI-PM_L1.2- PCI-PM_L1.1- ASPM_L1.2- ASPM_L1.1-
+			   T_CommonMode=0us LTR1.2_Threshold=0ns
+		L1SubCtl2: T_PwrOn=10us
+	Kernel driver in use: nvme
+	Kernel modules: nvme
+
+#+end_src
+
+A few things to note from this output:
++ *GT/s* is the number of transactions supported (here, 8 billion transactions / second). This is gen3 controller (gen1 is 2.5 and gen2 is 5)xs
++ *LNKCAP* is the capabilities which were communicated, and *LNKSTAT* is the current status. You want them to report the same values. If they don't, you are not using the hardware as it is intended (here I'm assuming the hardware is intended to work as a gen3 controller). In case the device is downgraded, the output will be like this: =LnkSta: Speed 2.5GT/s (downgraded), Width x16 (ok)=
++ *width* is the number of lanes that can be used by the device (here, we can use 4 lanes)
++ *MaxPayload* is the maximum size of a PCIe packet
+* Debugging
+PCI configuration registers can be used to debug various PCI bus issues.
+
+The various registers define bits that are either set (indicated with a '+') or unset (indicated with a '-'). These bits typically have attributes of 'RW1C' meaning you can read and write them and need to write a '1' to clear them. Because these are status bits, if you wanted to 'count' the occurrences of them you would need to write some software that detected the bits getting set, incremented counters, and cleared them over time.
+
+The 'Device Status Register' (DevSta) shows at a high level if there have been correctable errors detected (CorrErr), non-fatal errors detected (UncorrErr), fata errors detected (FataErr), unsupported requests detected (UnsuppReq), if the device requires auxillary power (AuxPwr), and if there are transactions pending (non posted requests that have not been completed).
+
+#+begin_src
+10000:01:00.0 Non-Volatile memory controller: Intel Corporation NVMe Datacenter SSD [3DNAND, Beta Rock Controller] (prog-if 02 [NVM Express])
+...
+        Capabilities: [100 v1] Advanced Error Reporting
+                UESta:  DLP- SDES- TLP- FCP- CmpltTO- CmpltAbrt- UnxCmplt- RxOF- MalfTLP- ECRC- UnsupReq- ACSViol-
+                UEMsk:  DLP- SDES- TLP- FCP- CmpltTO- CmpltAbrt- UnxCmplt- RxOF- MalfTLP- ECRC- UnsupReq- ACSViol-
+                UESvrt: DLP+ SDES+ TLP- FCP+ CmpltTO- CmpltAbrt- UnxCmplt- RxOF+ MalfTLP+ ECRC- UnsupReq- ACSViol-
+                CESta:  RxErr- BadTLP- BadDLLP- Rollover- Timeout- NonFatalErr-
+                CEMsk:  RxErr- BadTLP- BadDLLP- Rollover- Timeout- NonFatalErr+
+                AERCap: First Error Pointer: 00, GenCap+ CGenEn- ChkCap+ ChkEn-
+#+end_src
+
++ The Uncorrectable Error Status (UESta) reports error status of individual uncorrectable error sources (no bits are set
+  above):
+  + Data Link Protocol Error (DLP)
+  + Surprise Down Error (SDES)
+  + Poisoned TLP (TLP)
+  + Flow Control Protocol Error (FCP)
+  + Completion Timeout (CmpltTO)
+  + Completer Abort (CmpltAbrt)
+  + Unexpected Completion (UnxCmplt)
+  + Receiver Overflow (RxOF)
+  + Malformed TLP (MalfTLP)
+  + ECRC Error (ECRC)
+  + Unsupported Request Error (UnsupReq)
+  + ACS Violation (ACSViol)
++ The Uncorrectable Error Mask (UEMsk) controls reporting of individual errors by the device to the PCIe root complex. A
+  masked error (bit set) is not recorded or reported. Above shows no errors are being masked)
++ The Uncorrectable Severity controls whether an individual error is reported as a Non-fatal (clear) or Fatal error
+  (set).
++ The Correctable Error Status reports error status of individual correctable error sources: (no bits are set above)
+  + Receiver Error (RXErr)
+  + Bad TLP status (BadTLP)
+  + Bad DLLP status (BadDLLP)
+  + Replay Timer Timeout status (Timeout)
+  + REPLAY NUM Rollover status (Rollover)
+  + Advisory Non-Fatal Error (NonFatalIErr)
++ The Correctable Erro Mask (CEMsk) controls reporting of individual errors by the device to the PCIe root complex. A
+  masked error (bit set) is not reported to the RC. Above shows that Advisory Non-Fatal Errors are being masked - this
+  bit is set by default to enable compatibility with software that does not comprehend Role-Based error reporting.
++ The Advanced Error Capabilities and Control Register (AERCap) enables various capabilities (The above indicates the
+  device capable of generating ECRC errors but they are not enabled):
+  + First Error Pointer identifies the bit position of the first error reported in the Uncorrectable Error Status register
+  + ECRC Generation Capable (GenCap) indicates if set that the function is capable of generating ECRC
+  + ECRC Generation Enable (GenEn) indicates if ECRC generation is enabled (set)
+  + ECRC Check Capable (ChkCap) indicates if set that the function is capable of checking ECRC
+  + ECRC Check Enable (ChkEn) indicates if ECRC checking is enabled
diff --git a/users/fcuny/notes/content/notes/working-with-go.org b/users/fcuny/notes/content/notes/working-with-go.org
new file mode 100644
index 0000000..fd39d26
--- /dev/null
+++ b/users/fcuny/notes/content/notes/working-with-go.org
@@ -0,0 +1,213 @@
+#+TITLE: Working with Go
+#+DATE: <2021-08-05 Thu>
+#+TAGS[]: go emacs
+#+toc: t
+
+/This document assumes go version >= 1.16/.
+
+* Go Modules
+[[https://blog.golang.org/using-go-modules][Go modules]] have been added in 2019 with Go 1.11. A number of changes were introduced with [[https://blog.golang.org/go116-module-changes][Go 1.16]]. This document is a reference for me so that I can find answers to things I keep forgetting.
+** Creating a new module
+To create a new module, run =go mod init golang.fcuny.net/m=. This will create two files: =go.mod= and =go.sum=.
+
+In the =go.mod= file you'll find:
+- the module import path (prefixed with =module=)
+- the list of dependencies (within =require=)
+- the version of go to use for the module
+** Versioning
+To bump the version of a module:
+#+begin_src sh
+$ git tag v1.2.3
+$ git push --tags
+#+end_src
+
+Then as a user:
+#+begin_src sh
+$ go get -d golang.fcuny.net/m@v1.2.3
+#+end_src
+** Updating dependencies
+To update the dependencies, run =go mod tidy=
+** Editing a module
+If you need to modify a module, you can check out the module in your workspace (=git clone <module URL>=).
+
+Edit the =go.mod= file to add
+#+begin_src go
+replace <module URL> => <path of the local checkout>
+#+end_src
+
+Then modify the code of the module and the next time you compile the project, the cloned module will be used.
+
+This is particularly useful when trying to debug an issue with an external module.
+** Vendor-ing modules
+It's still possible to vendor modules by running =go mod vendor=. This can be useful in the case of a CI setup that does not have access to internet.
+** Proxy
+As of version 1.13, the variable =GOPROXY= defaults to =https://proxy.golang.org,direct= (see [[https://github.com/golang/go/blob/c95464f0ea3f87232b1f3937d1b37da6f335f336/src/cmd/go/internal/cfg/cfg.go#L269][here]]). As a result, when running something like =go get golang.org/x/tools/gopls@latest=, the request goes through the proxy.
+
+There's a number of ways to control the behavior, they are documented [[https://golang.org/ref/mod#private-modules][here]].
+
+There's a few interesting things that can be done when using the proxy. There's a few special URLs (better documentation [[https://golang.org/ref/mod#goproxy-protocol][here]]):
+| path                  | description                                                                              |
+|-----------------------+------------------------------------------------------------------------------------------|
+| $mod/@v/list          | Returns the list of known versions - there's one version per line and it's in plain text |
+| $mod/@v/$version.info | Returns metadata about a version in JSON format                                          |
+| $mod/@v/$version.mod  | Returns the =go.mod= file for that version                                                 |
+
+For example, looking at the most recent versions for =gopls=:
+#+begin_src sh
+; curl -s -L https://proxy.golang.org/golang.org/x/tools/gopls/@v/list|sort -r|head
+v0.7.1-pre.2
+v0.7.1-pre.1
+v0.7.1
+v0.7.0-pre.3
+v0.7.0-pre.2
+v0.7.0-pre.1
+v0.7.0
+v0.6.9-pre.1
+v0.6.9
+v0.6.8-pre.1
+#+end_src
+
+Let's check the details for the most recent version
+#+begin_src sh
+; curl -s -L https://proxy.golang.org/golang.org/x/tools/gopls/@v/list|sort -r|head
+v0.7.1-pre.2
+v0.7.1-pre.1
+v0.7.1
+v0.7.0-pre.3
+v0.7.0-pre.2
+v0.7.0-pre.1
+v0.7.0
+v0.6.9-pre.1
+v0.6.9
+v0.6.8-pre.1
+#+end_src
+
+And let's look at the content of the =go.mod= for that version too:
+#+begin_src sh
+; curl -s -L https://proxy.golang.org/golang.org/x/tools/gopls/@v/v0.7.1-pre.2.mod
+module golang.org/x/tools/gopls
+
+go 1.17
+
+require (
+        github.com/BurntSushi/toml v0.3.1 // indirect
+        github.com/google/go-cmp v0.5.5
+        github.com/google/safehtml v0.0.2 // indirect
+        github.com/jba/templatecheck v0.6.0
+        github.com/sanity-io/litter v1.5.0
+        github.com/sergi/go-diff v1.1.0
+        golang.org/x/mod v0.4.2
+        golang.org/x/sync v0.0.0-20210220032951-036812b2e83c // indirect
+        golang.org/x/sys v0.0.0-20210510120138-977fb7262007
+        golang.org/x/text v0.3.6 // indirect
+        golang.org/x/tools v0.1.6-0.20210802203754-9b21a8868e16
+        golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 // indirect
+        honnef.co/go/tools v0.2.0
+        mvdan.cc/gofumpt v0.1.1
+        mvdan.cc/xurls/v2 v2.2.0
+)
+#+end_src
+* Tooling
+** LSP
+=gopls= is the default implementation of the language server protocol maintained by the Go team. To install the latest version, run =go install golang.org/x/tools/gopls@latest=
+** =staticcheck=
+[[https://staticcheck.io/][=staticcheck=]] is a great tool to run against your code to find issues. To install the latest version, run =go install honnef.co/go/tools/cmd/staticcheck@latest=.
+* Emacs integration
+** =go-mode=
+[[https://github.com/dominikh/go-mode.el][This is the mode]] to install to get syntax highlighting (mostly).
+** Integration with LSP
+Emacs has a pretty good integration with LSP, and [[https://whatacold.io/blog/2022-01-22-emacs-eglot-lsp/]["Eglot for better programming experience in Emacs"]] is a good starting point.
+*** eglot
+[[https://github.com/joaotavora/eglot][This is the main mode to install]].
+
+The configuration is straightforward, this is what I use:
+#+begin_src elisp
+;; for go's LSP I want to use staticcheck and placeholders for completion
+(customize-set-variable 'eglot-workspace-configuration
+                        '((:gopls .
+                                  ((staticcheck     . t)
+                                   (matcher         . "CaseSensitive")
+                                   (usePlaceholders . t)))))
+
+;; ensure we load eglot for some specific modes
+(dolist (hook '(go-mode-hook nix-mode-hook))
+  (add-hook hook 'eglot-ensure))
+#+end_src
+
+=eglot= integrates well with existing modes for Emacs, mainly xref, flymake, eldoc.
+* Profiling
+** pprof
+[[https://github.com/google/pprof][pprof]] is a tool to visualize performance data. Let's start with the following test:
+#+begin_src go
+package main
+
+import (
+	"strings"
+	"testing"
+)
+
+func BenchmarkStringJoin(b *testing.B) {
+	input := []string{"a", "b"}
+	for i := 0; i <= b.N; i++ {
+		r := strings.Join(input, " ")
+		if r != "a b" {
+			b.Errorf("want a b got %s", r)
+		}
+	}
+}
+#+end_src
+
+Let's run a benchmark with ~go test . -bench=. -cpuprofile cpu_profile.out~:
+#+begin_src go
+goos: linux
+goarch: amd64
+pkg: golang.fcuny.net/m
+cpu: Intel(R) Core(TM) i3-1005G1 CPU @ 1.20GHz
+BenchmarkStringJoin-4           41833486                26.85 ns/op            3 B/op          1 allocs/op
+PASS
+ok      golang.fcuny.net/m      1.327s
+#+end_src
+
+And let's take a look at the profile with =go tool pprof cpu_profile.out=
+#+begin_src sh
+File: m.test
+Type: cpu
+Time: Aug 15, 2021 at 3:01pm (PDT)
+Duration: 1.31s, Total samples = 1.17s (89.61%)
+Entering interactive mode (type "help" for commands, "o" for options)
+(pprof) top
+Showing nodes accounting for 1100ms, 94.02% of 1170ms total
+Showing top 10 nodes out of 41
+      flat  flat%   sum%        cum   cum%
+     240ms 20.51% 20.51%      240ms 20.51%  runtime.memmove
+     220ms 18.80% 39.32%      320ms 27.35%  runtime.mallocgc
+     130ms 11.11% 50.43%      450ms 38.46%  runtime.makeslice
+     110ms  9.40% 59.83%     1150ms 98.29%  golang.fcuny.net/m.BenchmarkStringJoin
+     110ms  9.40% 69.23%      580ms 49.57%  strings.(*Builder).grow (inline)
+     110ms  9.40% 78.63%     1040ms 88.89%  strings.Join
+      70ms  5.98% 84.62%      300ms 25.64%  strings.(*Builder).WriteString
+      50ms  4.27% 88.89%      630ms 53.85%  strings.(*Builder).Grow (inline)
+      40ms  3.42% 92.31%       40ms  3.42%  runtime.nextFreeFast (inline)
+      20ms  1.71% 94.02%       20ms  1.71%  runtime.getMCache (inline)
+#+end_src
+
+We can get a breakdown of the data for our module:
+#+begin_src sh
+(pprof) list golang.fcuny.net
+Total: 1.17s
+ROUTINE ======================== golang.fcuny.net/m.BenchmarkStringJoin in /home/fcuny/workspace/gobench/app_test.go
+     110ms      1.15s (flat, cum) 98.29% of Total
+         .          .      5:   "testing"
+         .          .      6:)
+         .          .      7:
+         .          .      8:func BenchmarkStringJoin(b *testing.B) {
+         .          .      9:   b.ReportAllocs()
+      10ms       10ms     10:   input := []string{"a", "b"}
+         .          .     11:   for i := 0; i <= b.N; i++ {
+      20ms      1.06s     12:           r := strings.Join(input, " ")
+      80ms       80ms     13:           if r != "a b" {
+         .          .     14:                   b.Errorf("want a b got %s", r)
+         .          .     15:           }
+         .          .     16:   }
+         .          .     17:}
+#+end_src
diff --git a/users/fcuny/notes/content/notes/working-with-nix.org b/users/fcuny/notes/content/notes/working-with-nix.org
new file mode 100644
index 0000000..105d025
--- /dev/null
+++ b/users/fcuny/notes/content/notes/working-with-nix.org
@@ -0,0 +1,26 @@
+#+TITLE: Working with nix
+#+DATE: <2022-05-10 Tue>
+#+TAGS[]: linux nix
+
+* the =nix develop= command
+The =nix develop= command is for working on a repository. If our repository contains a =Makefile=, it will be used by the various sub-commands.
+
+=nix develop= supports multiple [[https://nixos.org/manual/nixpkgs/stable/#sec-stdenv-phases][phases]] and they map as follow:
+
+| phase          | default to   | command                 | note |
+|----------------+--------------+-------------------------+------|
+| configurePhase | =./configure=  | =nix develop --configure= |      |
+| buildPhase     | =make=         | =nix develop --build=     |      |
+| checkPhase     | =make check=   | =nix develop --check=     |      |
+| installPhase   | =make install= | =nix develop --install=   |      |
+
+In the repository, running =nix develop --build= will build the binary *using the Makefile*. This is different from running =nix build=.
+
+* the =nix build= and =nix run= commands
+** for Go
+For Go, there's the =buildGoModule=. Looking at the [[https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/go-modules/generic/default.nix][source]] we can see there's a definition of what will be done for each phases. As a result, we don't have to define them ourselves.
+
+If we run =nix build= in the repository, it will run the default [[https://github.com/NixOS/nixpkgs/blob/fb7287e6d2d2684520f756639846ee07f6287caa/pkgs/development/go-modules/generic/default.nix#L171][build phase]].
+* =buildInputs= or =nativeBuildInputs=
++ =nativeBuildInputs= is intended for architecture-dependent build-time-only dependencies
++ =buildInputs= is intended for architecture-independent build-time-only dependencies
diff --git a/users/fcuny/notes/flake.lock b/users/fcuny/notes/flake.lock
new file mode 100644
index 0000000..afaae62
--- /dev/null
+++ b/users/fcuny/notes/flake.lock
@@ -0,0 +1,42 @@
+{
+  "nodes": {
+    "flake-utils": {
+      "locked": {
+        "lastModified": 1649676176,
+        "narHash": "sha256-OWKJratjt2RW151VUlJPRALb7OU2S5s+f0vLj4o1bHM=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "a4b154ebbdc88c8498a5c7b01589addc9e9cb678",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1652295142,
+        "narHash": "sha256-vqvZa2xoNPhkpAhAbtUCA2wyga1qv6QeuGH2C8IVnus=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "174c43d7d17b27e50074fe3c970a5659a4d8e39b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/users/fcuny/notes/flake.nix b/users/fcuny/notes/flake.nix
new file mode 100644
index 0000000..52e25c1
--- /dev/null
+++ b/users/fcuny/notes/flake.nix
@@ -0,0 +1,46 @@
+{
+  description = "Franck Cuny's notes.";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let pkgs = nixpkgs.legacyPackages.${system};
+      in {
+        defaultPackage = with pkgs;
+          stdenv.mkDerivation {
+            pname = "notes.fcuny.net";
+            version = self.lastModifiedDate;
+            src = ./.;
+            buildInputs = [ hugo git ];
+            buildPhase = ''
+              mkdir -p $out
+              hugo --minify --destination $out
+            '';
+            dontInstall = true;
+          };
+
+        defaultApp = pkgs.writers.writeBashBin "run-hugo" ''
+          set -e
+          set -o pipefail
+          export PATH=${pkgs.lib.makeBinPath [ pkgs.hugo pkgs.git ]}
+          hugo server -D
+        '';
+
+        apps = {
+          deploy = pkgs.pkgs.writeShellScriptBin "run-deploy" ''
+            set -euxo pipefail
+            export PATH=${
+              pkgs.lib.makeBinPath [ pkgs.hugo pkgs.git pkgs.jq pkgs.flyctl ]
+            }:$PATH
+            bash ./scripts/deploy.sh
+          '';
+        };
+
+        devShell =
+          pkgs.mkShell { buildInputs = with pkgs; [ hugo flyctl git jq ]; };
+      });
+}
diff --git a/users/fcuny/notes/fly.toml b/users/fcuny/notes/fly.toml
new file mode 100644
index 0000000..4db1311
--- /dev/null
+++ b/users/fcuny/notes/fly.toml
@@ -0,0 +1,37 @@
+# fly.toml file generated for notes-fcunynet on 2022-03-28T19:44:54-07:00
+
+app = "notes-fcunynet"
+
+kill_signal = "SIGINT"
+kill_timeout = 5
+
+[env]
+
+[experimental]
+  allowed_public_ports = []
+  auto_rollback = true
+
+[[services]]
+  http_checks = []
+  internal_port = 8080
+  protocol = "tcp"
+  script_checks = []
+
+  [services.concurrency]
+    hard_limit = 25
+    soft_limit = 20
+    type = "connections"
+
+  [[services.ports]]
+    handlers = ["http"]
+    port = 80
+
+  [[services.ports]]
+    handlers = ["tls", "http"]
+    port = 443
+
+  [[services.tcp_checks]]
+    grace_period = "1s"
+    interval = "15s"
+    restart_limit = 6
+    timeout = "2s"
diff --git a/users/fcuny/notes/layouts/_default/baseof.html b/users/fcuny/notes/layouts/_default/baseof.html
new file mode 100644
index 0000000..0c72fb1
--- /dev/null
+++ b/users/fcuny/notes/layouts/_default/baseof.html
@@ -0,0 +1,10 @@
+<!doctype html>
+<html lang="en">
+  {{ partial "head.html" . }}
+  <body>
+    {{- partial "header.html" . -}}
+    <main>
+     {{ block "main" . }}{{ end }}
+    </main>
+  </body>
+</html>
diff --git a/users/fcuny/notes/layouts/_default/list.html b/users/fcuny/notes/layouts/_default/list.html
new file mode 100644
index 0000000..d2c59a7
--- /dev/null
+++ b/users/fcuny/notes/layouts/_default/list.html
@@ -0,0 +1,10 @@
+{{ define "main" }}
+
+<article>
+
+  {{ $pgs := where .Data.Pages "Params.hidden" "ne" "true" }}
+  {{ partial "postlist" $pgs }}
+
+</article>
+
+{{ end }}
diff --git a/users/fcuny/notes/layouts/_default/single.html b/users/fcuny/notes/layouts/_default/single.html
new file mode 100644
index 0000000..7f594ad
--- /dev/null
+++ b/users/fcuny/notes/layouts/_default/single.html
@@ -0,0 +1,40 @@
+{{ define "main" }}
+
+<div>
+
+<h1>{{ .Title }}</h1>
+
+<div id="meta">
+  {{- $pub := .Date.Format "Jan 2, 2006" -}}
+  {{- $mod := "" -}}
+  {{- if (not .GitInfo) }}
+  {{- $mod = .Lastmod.Format "Jan 2, 2006" -}}
+  {{ else }}
+  {{- $mod = .Page.GitInfo.CommitDate.Format "Jan 2, 2006" -}}
+  {{ end -}}
+  {{ if eq $pub $mod }}
+  <div id="meta_date">published {{ $pub }}</div>
+  {{ else }}
+  <div id="meta_date">published {{ $pub }} - last modified {{ $mod }}</div>
+  {{ end }}
+  {{ if .Params.tags }}
+  <div>
+  {{ if eq (len .Params.tags) 1 }}
+  tag:
+  {{ else }}
+  tags:
+  {{ end }}
+  {{ range $idx, $tag := .Params.tags }}
+  <span id="meta_tags"><a href="/tags/{{ $tag | urlize }}/">{{ $tag }}</a></span>
+  {{ end }}
+  </div>
+  {{ end }}
+</div>
+
+<article>
+{{ .Content }}
+</article>
+
+</div>
+
+{{ end }}
diff --git a/users/fcuny/notes/layouts/index.html b/users/fcuny/notes/layouts/index.html
new file mode 100644
index 0000000..8ddc67d
--- /dev/null
+++ b/users/fcuny/notes/layouts/index.html
@@ -0,0 +1,22 @@
+{{ define "main" }}
+
+<article>
+
+  A place to collect random notes.
+
+  <ul id="post-permalink">
+  {{- $pages := where site.RegularPages "Type" "in" site.Params.mainSections }}
+  {{ range $pages }}
+  <li>
+    <a href="{{ .Permalink }}">{{ .Title }}</a>
+    {{ range $idx, $tag := .Params.tags }}
+    <span id="meta_tags"><a href="/tags/{{ $tag | urlize }}/">{{ $tag }}</a></span>
+  {{ end }}
+  </li>
+
+  {{ end }}
+  </ul>
+
+</article>
+
+{{ end }}
diff --git a/users/fcuny/notes/layouts/partials/head.html b/users/fcuny/notes/layouts/partials/head.html
new file mode 100644
index 0000000..6e5a6fb
--- /dev/null
+++ b/users/fcuny/notes/layouts/partials/head.html
@@ -0,0 +1,17 @@
+<head>
+  <meta charset="utf-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+
+  <link rel="canonical" href="{{ .Permalink }}">
+
+  {{ $css := "/css/custom.css"  }}
+  <link rel="stylesheet" href="{{ $css }}">
+  <link rel="author" href="humans.txt" />
+
+  <link rel="icon" href="data:image/svg+xml,<svg xmlns=%22http://www.w3.org/2000/svg%22 viewBox=%220 0 100 100%22><text y=%22.9em%22 font-size=%2290%22>🖥️</text></svg>">
+
+  <meta name="description" content="Franck's notes.">
+  <meta name="author" content="Franck Cuny">
+
+  <title>{{ .Title }}</title>
+</head>
diff --git a/users/fcuny/notes/layouts/partials/header.html b/users/fcuny/notes/layouts/partials/header.html
new file mode 100644
index 0000000..798463c
--- /dev/null
+++ b/users/fcuny/notes/layouts/partials/header.html
@@ -0,0 +1,5 @@
+<header>
+  <nav class="navbar">
+    <a class="nav-bold" href="{{ .Site.BaseURL }}">~/notes</a>
+  </nav>
+</header>
diff --git a/users/fcuny/notes/layouts/partials/postlist.html b/users/fcuny/notes/layouts/partials/postlist.html
new file mode 100644
index 0000000..3d5cf04
--- /dev/null
+++ b/users/fcuny/notes/layouts/partials/postlist.html
@@ -0,0 +1,12 @@
+{{ range .GroupByDate "2006" }}
+  <h2>{{ .Key }}</h2>
+  <ul>
+    {{ range .Pages.ByDate.Reverse }}
+    <li>
+      <div>
+        <a href="{{ .Permalink }}">{{ .Title }}</a>
+      </div>
+    </li>
+    {{ end }}
+  </ul>
+{{ end }}
diff --git a/users/fcuny/notes/layouts/taxonomy/tag.html b/users/fcuny/notes/layouts/taxonomy/tag.html
new file mode 100644
index 0000000..2b7d98a
--- /dev/null
+++ b/users/fcuny/notes/layouts/taxonomy/tag.html
@@ -0,0 +1,6 @@
+{{ define "main" }}
+
+  {{ $pgs := where .Data.Pages "Params.hidden" "ne" "true" }}
+  {{ partial "postlist" $pgs }}
+
+{{ end }}
diff --git a/users/fcuny/notes/scripts/deploy.sh b/users/fcuny/notes/scripts/deploy.sh
new file mode 100755
index 0000000..4075f08
--- /dev/null
+++ b/users/fcuny/notes/scripts/deploy.sh
@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+
+git diff --exit-code
+git diff --staged --exit-code
+
+flyctl deploy
+
+VERSION=$(flyctl info -j |jq -r '.App | "notes.fcuny.net/v\(.Version)"')
+
+git tag -a --message ${VERSION} ${VERSION}
+git push origin --all
+git push origin --tags
+
+flyctl agent stop
diff --git a/users/fcuny/notes/static/CNAME b/users/fcuny/notes/static/CNAME
new file mode 100644
index 0000000..5f43d63
--- /dev/null
+++ b/users/fcuny/notes/static/CNAME
@@ -0,0 +1 @@
+notes.fcuny.net
diff --git a/users/fcuny/notes/static/css/custom.css b/users/fcuny/notes/static/css/custom.css
new file mode 100644
index 0000000..e02631a
--- /dev/null
+++ b/users/fcuny/notes/static/css/custom.css
@@ -0,0 +1,194 @@
+html {
+  margin-left: 2em;
+  margin-right: 0em;
+  margin-top: 1em;
+}
+
+body {
+  font-family: monospace;
+  font-size: 1.15em;
+  line-height: 1.5em;
+  color: #0e0e0b;
+  padding: 0 0.55em;
+  max-width: 60rem;
+}
+
+h1 {
+  color: #0e0e0b;
+  font-size: 2rem;
+  margin-top: 1em;
+  margin-bottom: 0.34em;
+}
+
+h2, h3 {
+  border-bottom: 1px solid #eee;
+  font-style: italic;
+}
+h2 {
+  margin-top: 1.25em;
+  margin-bottom: 0.41em;
+  font-size: 1.4rem;
+}
+h3 {
+  margin-top: 1.5em;
+  margin-bottom: 0.5em;
+  font-size: 1.2rem;
+}
+
+hr{
+  color:#000111;
+  background-color:#000111;
+  border:none;
+  height:1px
+}
+
+a {
+  color:#047bc2;
+  transition:color .1s ease-in-out;
+}
+
+a:link,
+a:hover,
+a:focus,
+a:active {
+  color:#047bc2;
+  text-decoration: underline;
+  text-underline-offset:.2rem
+}
+
+span.published, span.updated {
+  display: center;
+  font-style: oblique;
+}
+
+code {
+  font-family: monospace;
+  padding-left: 0.2em;
+  padding-right: 0.2em;
+  border-radius: 4px;
+}
+
+p code {
+  color: black;
+  background-color: #eee;
+  padding: 0 0.2rem;
+  font-size: 1.1em;
+}
+
+pre {
+  font-family: monospace;
+  font-size: 1.1em;
+  margin: 0;
+  word-wrap: normal;
+  padding: 0.8em;
+  overflow-x: auto;
+  border: 1px solid #eee;
+  border-radius: 3px;
+  background-color: #fafafa;
+}
+
+#meta {
+  display: row;
+}
+
+#meta_tags {
+  padding: 0 .5rem;
+  font-size: 0.8rem;
+  border: 2px solid #eee;
+  background-color: #eee;
+}
+
+#meta_tags a {
+  text-decoration: none;
+  border-bottom: none;
+  color: #005a9c;
+}
+
+#meta_date {
+  font-style: italic;
+  font-size: 0.8rem;
+}
+
+table {
+  width: 100%;
+  border-spacing: px;
+  outline: none;
+}
+
+td{
+  padding-left: 0.4em;
+  padding-top: 0.4em;
+  padding-bottom: 0.4em;
+}
+thead {
+  color: #000;
+  font-style: bold;
+  text-align: left;
+}
+table, th, td {
+  font-family: monospace;
+  border: 1px solid;
+  border-collapse: collapse;
+  color: #000;
+}
+
+blockquote {
+  font-size: 0.95rem;
+  font-style: italic;
+  margin: 0 0 1.5em;
+  padding-left: 1em;
+  border-left: .2em solid #bdbdbd
+}
+
+nav {
+  padding-right: 10px;
+  font-size: 1.4em;
+  display: flex;
+  font-family: monospace;
+  justify-content: space-between;
+  align-items: center;
+  padding-top: 0.5rem;
+}
+
+.nav-links {
+  list-style: none;
+  display: flex;
+}
+
+.navbar a {
+  display: inline-block;
+  text-decoration: none;
+}
+
+.navbar a:hover {
+  background-color: #b72d2d;
+  color: #fafafa;
+  text-decoration: none;
+}
+
+.nav-bold {
+  font-weight: 700;
+  color: #b72d2d;
+  text-decoration: none;
+}
+
+article {
+  text-align: justify;
+  padding-top: 2em;
+}
+
+#post-permalink {
+  list-style-type: none;
+  padding-left: 0;
+}
+
+#post-permalink>li {
+ line-height:1.2rem;
+ margin:.6rem 0
+}
+
+.post-date {
+  font-family: monospace;
+  font-weight: 400;
+  font-size: 1.1em;
+}
diff --git a/users/fcuny/notes/static/humans.txt b/users/fcuny/notes/static/humans.txt
new file mode 100644
index 0000000..d2c9d47
--- /dev/null
+++ b/users/fcuny/notes/static/humans.txt
@@ -0,0 +1,10 @@
+/* TEAM */
+Author: Franck Cuny
+Contact: franck [at] fcuny.net
+Twitter: @franckcuny
+Location: Berkeley, CA
+
+/* SITE */
+CA: Let's Encrypt
+Host: Fly.io
+Serving: Linux, Go