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Platform Image

NOTICE: This is a work in progress. This document is terse to convey intent that exists at the time it was written. Things may change.

The platform image is based on Debian utilizing ZFS on Linux.

Build Machine Requirements

TLDR

  1. Install Debian 10 64-bit on a machine (e.g. in VMware)

  2. Install ZFS

  3. Create a zpool (warning - this will destroy the disk partition), e.g.

    zpool create data /dev/sdb
sudo touch /data/.system_pool

  4. Install Git

    apt install -y git

  5. Build the Image - clone this repo and run the debian-live image builder:

    git clone https://github.com/TritonDataCenter/linux-live
cd linux-live
./tools/debian-live

  6. Copy the resulting image (ISO or USB) out of the Debian machine and use that for the compute node boot (e.g. in a different VMware virtual machine, or on real hardware).

Image Contents

The root file system of the image will be a squashfs image that is mounted with a tmpfs overlay, allowing the root file system to be read-write. Since the overlay is backed by tmpfs, it is not persisted across reboots.

There are a small number of Triton-specific files that need to be delivered into the image. In general they fall into the following categories:

  • Things needed to bootstrap Triton. For instance, ur-agent and its dependencies (e.g. /usr/node) need to be present.
  • Things needed for sane operation. Currently this includes:
    • Setting the locale to quiet various warnings.
    • Fixing a very poor default setting for mouse in vim so that copy and paste will work.
    • Adding Triton paths to $PATH
    • Use of DHCP when booted as not part of Triton
    • SSH host key generation and preservation
    • Altering service dependencies so that service configuration stored in ZFS is respected.
    • Generate the same hostid every time to keep ZFS happy.
    • Utilities that SmartOS admins expect to have. This includes json and bunyan, among other things.

As much as possible, Triton components that are part of the image are installed under /usr/triton. When needed, symbolic links should be installed for compatibility. For instance, much of Triton software may assume that /usr/node/bin/node is the platform's node installation, so /usr/node is a symbolic link to the appropriate directory under /usr/triton.

Files used for configuring systemd (service files, drop-ins, etc.) are installed under /usr/lib/systemd.

Special effort is made to keep some directories empty so that ZFS file systems can be mounted over them. For instance, persistent network configuration is stored as drop-in files in /etc/systemd/network, which is mounted from <system pool>/platform/etc/systemd/network.

Several conventions from SmartOS have been carried forward to Linux. This includes, but is not limited to:

  • noimport=true boot parameter will skip importing pools
  • destroy_zpools=true will destroy the system pool at boot
  • marking zones/var for factory reset will destroy the system pool at boot
  • sdc-factoryreset will mark zones/var for reset
  • /opt/custom. This includes /opt/custom/systemd for custom unit files

Image Distribution

Initially images will be available via Manta. At a later time, these will be distributed via updates.tritondatacenter.com.

Platform Image Import

The layout of a Linux platform.tgz file will be:

platform/
platform/etc/
platform/etc/version/
platform/etc/version/platform
platform/etc/version/os-release
platform/etc/version/gitstatus
platform/x86_64/vmlinuz
platform/x86_64/initrd
platform/x86_64/initrd.hash
platform/x86_64/filesystem.squashfs
platform/x86_64/filesystem.squashfs.hash
platform/x86_64/filesystem.packages
platform/x86_64/filesystem.manifest
platform/x86_64/build.tgz
platform/x86_64/build.tgz.hash
platform/x86_64/build.tgz.packages
platform/x86_64/build.tgz.manifest

The existing sdcadm platform command is used to install Linux platform images.

sdcadm platform install /path/to/image.tar.gz

iPXE configuration

When a Linux platform is assigned to a CN, the following files will be configured in the dhcpd zone under /tftboot:

  • menu.lst.01<MAC>: grub configuration (legacy configuration)
  • boot.ipxe.01<MAC>: ipxe configuration
  • bootfs/<MAC>/networking.json: same as SmartOS

Note: Triton compute nodes will boot Loader from the USB first, then load iPXE and chain load the boot.ipxe file. Chain loading grub is legacy, but still supported. In most cases it is not needed and should not be used.

boot.ipxe.01<MAC> will resemble:

#!ipxe
kernel /os/20210731T223008Z/platform/x86_64/vmlinuz boot=live console=tty0 console=ttyS1,115200n8 <EXTRA OPTS> fetch=http://10.33.166.12/os/20210731T223008Z/platform/x86_64/filesystem.squashfs
initrd http://<booter>/os/20210731T223008Z/platform/x86_64/initrd
module http://<booter>/extra/joysetup/node.config /etc/node.config
module http://${next-server}/bootfs/<MAC>/networking.json /etc/triton-networking.json
module http://${next-server}/bootfs/<MAC>/networking.json.hash /etc/triton-networking.json.hash
boot

This example assumes that booter is configured to serve files via HTTP, not TFTP. The current Triton default is for HTTP boot, and can significantly speed up boot times. If you have an older Triton installation and would like to switch to HTTP boot, use the following commands:

dhcpd_svc=$(sdc-sapi /services?name=dhcpd | json -Ha uuid)
sapiadm update "$dhcpd_svc" metadata.http_pxe_boot=true

Boot Procedure

The boot of a Linux CN via iPXE uses the following general procedure:

  1. ipxe downloads /os/<platform-timestamp>/platform/x86_64/vmlinuz as the kernel.
  2. ipxe downloads /os/<platform-timestamp>/platform/x86_64/initrd.img as the initial ramdisk.
  3. ipxe downloads /bootfs/<MAC>/network.json as /networking.json
  4. The kernel starts, loads initrd.img into a initramfs and mounts at /. /networking.json and /packages.tar are visible.
  5. The live-boot scripts download filesystem.squashfs and creates the required overlay mounts to make it writable.
  6. /networking.json is moved to a location that will be accessible in the new root. This is at a path that a systemd generator will find it to generate the appropriate networking configuration under /run/systemd.
  7. live-boot pivots root and transfers control to systemd.

Boot of a new CN

A new CN will boot the default image, which may be a SmartOS or a Linux image. The server may need to be explicitly assigned a linux platform image via sdcadm platform assign and rebooted to the desired operating system before proceeding with sdc-server setup.

Platform Image creation

As stated earlier in this document, in general the image creation process is roughly:

git clone https://github.com/TritonDataCenter/linux-live
cd linux-live
sudo tools/debian-live

If all goes well, the final few lines will tell you what the name of the generated .iso and .usb.gz files are.

Build machine installation

The debian-live image can be created on an existing debian-live system. The tools/debian-live script can install the necessary dependencies.

Build machine installation is Triton Linux

The build process is self-hosting. The first image needs to be created elsewhere - a Debian 10 (64 bit) box with the right packages well do. Once your organization has the first image, it is probably easiest to go with the self hosting route.

Build machine installation is not Triton Linux

If your organization has not yet built its own image, you will need to use a generic Debian 10 system to build the the first image. The procedure is as follows.

/bin/sh

Debian uses dash as the Bourne shell. It is less featureful than bash, which causes problems for some Triton Makefiles. To work around this:

Over time, each problematic Makefile should be changed to include:

SHELL = /bin/bash

Note that /bin/bash works across various Linux distros and SmartOS. /usr/bin/bash does not exist on at least some Linux distros.

Install ZFS

See https://wiki.debian.org/ZFS#Installation or some other "Getting Started" link found at https://zfsonlinux.org/. For licensing reasons, the installation will need to build ZFS, which will take several minutes.

First boot build machine setup

Once you have a Debian instance with ZFS, perform the following steps.

Create a zpool

For now, the image creation script assumes that there is a pool named triton where it can create images.

sudo zpool create data /dev/vdb

If you will be developing and testing agents on this box, you probably want to tell them that your pool is the system pool.

sudo touch /data/.system_pool

Install other dependencies

Note: This step assumes you you have a non-root user with a home directory on a persistent file system (ZFS, ext4, etc.) so that it survives reboots. If running on debian-live, see 4-zfs.md and look for sysusers.

Run the preflight check to see what other things you need. If it tells you to install other packages, do the needful.

$ git clone https://github.com/TritonDataCenter/linux-live
$ cd linux-live
$ ./tools/debian-live preflight_check
$ echo $?
0

Special steps for development on debian-live

If you are developing on debian-live, the additional software that you install to build the image or other software will not survive reboot. You will need to follow the advice given by debian-live preflight_check after each reboot.

Advanced debian-live use and development

This section talks a bit more about the structure of this repository and the use of the debian-live script.

Repository structure

The repository has the following directories that largely conform to what you would expect from a Triton repository.

  • doc: the directory containing the file you are reading now.
  • proto: extra files that are copied directly into the repository. In addition, each systemd service that is included in proto/usr/lib/systemd/system is enabled in the image. That is, the files are delivered into the image, then the appropriate systemd symbolic links are created.
  • tools: home to the debian-live script and perhaps other tools.

Iterative development

As stated above, the typical way that an image is built is with:

sudo tools/debian-live

That's great when things will be smooth sailing from start to finish. However, some of the early steps take several minutes to complete. When tweaking files in the proto directory, it is quite annoying to have to wait for a ZFS build to fix a typo in a file. For this reason, the build can be rolled back to the beginning of any stage so that stage (and presumably others) can be executed.

To list the available stages, use tools/debian-live -h:

$ ./tools/debian-live -h
./tools/debian-live: illegal option -- h
Usage:
Create a new image from scratch
    debian-live

Run just the specified steps on an existing image build
    debian-live -r release step [...]

Valid steps are:
    preflight_check
    create_bootstrap
    install_live
    build_zfs
    reduce_zfs
    install_usr_triton
    install_proto
    postinstall
    prepare_archive_bits
    create_iso
    create_usb
    ...

Literal ... may be used to specify all remaining steps.

If I only want to roll back to before install_proto and re-run that step:

$ zfs list -Ho name | grep debian-live | tail -1
triton/debian-live-20200105T222739Z

$ sudo tools/debian-live -r 20200105T222739Z install_proto

To inspect the outcome of that, you can chroot /data/debian-live/<platform_stamp>/chroot and poke around. More commonly you will want to run install_proto and all steps after it. You can use ... for that.

sudo tools/debian-live -r 20200105T222739Z install_proto ...