Catalyst/Custom Media Image

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Catalyst can be used to make bootable ISOs.

This guide describes the process used to create an install ISO similar to ones created by project:RelEng. A basic understanding of Catalyst will help to follow this guide.

Important
References to stages are unique to this LiveCD build process, and reflect stages in the build process, and are not to be confused with stage files.

For this process, stage1 refers to the base image, which is the core of the LiveCD, while stage2 is the build/packaging process to make that into a bootable ISO.

Build Environment Setup

Installing Catalyst

Install dev-util/catalyst making sure the iso USE flag (enabled by default) is set:

root #emerge --ask dev-util/catalyst

Obtaining RelEng config

This build process is based on RelEng config which is available by git:

/home/larry/gitstuff $git clone -o upstream https://github.com/gentoo/releng.git
Important
The path of this config repo will be used to substitute @REPODIR@ for setting the portage_confdir within specs.

Generating a Portage Snapshot

From the Catalyst build directory, a new portage snapshot can be generated with:

/var/tmp/catalyst #catalyst -s stable
16 Sep 2024 19:04:57 CDT: NOTICE  : Loading configuration file: /etc/catalyst/catalyst.conf
NOTICE:catalyst:Loading configuration file: /etc/catalyst/catalyst.conf
16 Sep 2024 19:04:57 CDT: NOTICE  : conf_values[options] = ['autoresume', 'bindist', 'kerncache', 'pkgcache', 'seedcache']
NOTICE:catalyst:conf_values[options] = ['autoresume', 'bindist', 'kerncache', 'pkgcache', 'seedcache']
16 Sep 2024 19:04:57 CDT: NOTICE  : >>> /usr/sbin/git clone --quiet --depth=1 --bare -c gc.reflogExpire=0 -c gc.reflogExpireUnreachable=0 -c gc.rerereresolved=0 -c gc.rerereunresolved=0 -c gc.pruneExpire=now --branch=stable https://anongit.gentoo.org/git/repo/sync/gentoo.git /var/tmp/catalyst/repos/gentoo.git
NOTICE:catalyst:>>> /usr/sbin/git clone --quiet --depth=1 --bare -c gc.reflogExpire=0 -c gc.reflogExpireUnreachable=0 -c gc.rerereresolved=0 -c gc.rerereunresolved=0 -c gc.pruneExpire=now --branch=stable https://anongit.gentoo.org/git/repo/sync/gentoo.git /var/tmp/catalyst/repos/gentoo.git
16 Sep 2024 19:05:21 CDT: NOTICE  : Creating gentoo tree snapshot 3e5f2241174dbb89608c4766ca949e77cdca7b70 from /var/tmp/catalyst/repos/gentoo.git
NOTICE:catalyst:Creating gentoo tree snapshot 3e5f2241174dbb89608c4766ca949e77cdca7b70 from /var/tmp/catalyst/repos/gentoo.git
16 Sep 2024 19:05:21 CDT: NOTICE  : >>> /usr/sbin/git -C /var/tmp/catalyst/repos/gentoo.git archive --format=tar 3e5f2241174dbb89608c4766ca949e77cdca7b70 |
NOTICE:catalyst:>>> /usr/sbin/git -C /var/tmp/catalyst/repos/gentoo.git archive --format=tar 3e5f2241174dbb89608c4766ca949e77cdca7b70 |
16 Sep 2024 19:05:21 CDT: NOTICE  :     /usr/sbin/tar2sqfs /var/tmp/catalyst/snapshots/gentoo-3e5f2241174dbb89608c4766ca949e77cdca7b70.sqfs -q -f -j1 -c gzip
NOTICE:catalyst:    /usr/sbin/tar2sqfs /var/tmp/catalyst/snapshots/gentoo-3e5f2241174dbb89608c4766ca949e77cdca7b70.sqfs -q -f -j1 -c gzip
16 Sep 2024 19:05:25 CDT: NOTICE  : Wrote snapshot to /var/tmp/catalyst/snapshots/gentoo-3e5f2241174dbb89608c4766ca949e77cdca7b70.sqfs
NOTICE:catalyst:Wrote snapshot to /var/tmp/catalyst/snapshots/gentoo-3e5f2241174dbb89608c4766ca949e77cdca7b70.sqfs
Important
Pay close attention to the output of this command, looking for Wrote snapshot to: . This line contains the snapshot_treeish which is required for the stage1 spec.

In this case, the snapshot_treeish is 3e5f2241174dbb89608c4766ca949e77cdca7b70

Obtaining a stage3 seed

Catalyst looks for seed files under /var/tmp/catalyst/builds/<stage3>, a directory must be created for these if not already present:

root #mkdir -p /var/tmp/catalyst/builds/23.0-default
Tip
The actual subpath under builds can be set arbitrarily, but is set to 23.0-default to match the one defined in the RelEng spec.

A seed stage3 is needed to build the LiveCD, stage files can be found on the downloads page or from mirrors:

Note
In this example stage3-amd64-openrc-20240915T163400Z.tar.xz is used, but a new release will likely exist. The timestamp 20240915T163400Z will be used later for stage 1 spec config.
Tip
If building a LiveGUI, using a desktop profile image is preferred.

Staging the LiveCD spec files

Specs for the stage 1 and stage 2 are provided in the previously cloned git repo. Specs should be available in the cloned git repo, under releases/specs/<arch>:

releng $ls releases/specs/amd64/installcd*
releases/specs/amd64/installcd-stage1.spec  releases/specs/amd64/installcd-stage2-minimal.spec

These spec files can be copied to /var/tmp/catalyst with:

releng #cp releases/specs/amd64/installcd* /var/tmp/catalyst

Optional: Staging the LiveGUI spec files

To use the larger LiveGUI specs, available under releases/specs/<arch>/livegui:

releng #cp releases/specs/amd64/livegui/*.spec /var/tmp/catalyst

Template vars

Before being used, RelEng specs must be edited, as a few template vars are present, enclosed in @'s:

  • TIMESTAMP - The release timestamp used in the version_stamp and source_subpath, e.g. 20240915T163400Z.
  • DATESTAMP - The release date, used for the LiveCD volume label, e.g. 2024-09-15.
  • TREEISH - The snapshot_treeish hash, e.g. 3e5f2241174dbb89608c4766ca949e77cdca7b70.
  • REPO_DIR - The base path to the releng config for portage_confdir, e.g. /home/larry/gitstuff/releng.
Note
These variables would typically be substituted by catalyst-auto.

Stage1

The first build step is to create the stage 1 which is built off of the selected seed stage 3 and based on the provided spec.

Preparing the Stage1 Spec File

When used manually, a few key fields must be edited to make RelEng provided spec files usable, these include:

  • version_stamp - The version string used for the catalyst build, can be set arbitrarily.
  • rel_type - The release type, used to set the sub-directory under /var/tmp/catalyst/builds.
  • snapshot_treeish - The treeish for the portage snapshot.
  • source_subpath - The source for the stage3 seed.
  • portage_confdir - The config dir for the build environment.
FILE /var/tmp/catalyst/installcd-stage1.specLiveCD stage 1 base template.
subarch: amd64
version_stamp: @TIMESTAMP@
target: livecd-stage1
rel_type: 23.0-default
profile: default/linux/amd64/23.0/no-multilib
snapshot_treeish: @TREEISH@
source_subpath: 23.0-default/stage3-amd64-openrc-@TIMESTAMP@
compression_mode: pixz
portage_confdir: @REPO_DIR@/releases/portage/isos
FILE /var/tmp/catalyst/installcd-stage1.specLiveCD stage 1 filled template.
subarch: amd64
version_stamp: custom_livecd
target: livecd-stage1
rel_type: 23.0-default
profile: default/linux/amd64/23.0/no-multilib
snapshot_treeish: 3e5f2241174dbb89608c4766ca949e77cdca7b70
source_subpath: 23.0-default/stage3-amd64-openrc-20240915T163400Z
compression_mode: pixz
portage_confdir: /home/larry/gitstuff/releng/releases/portage/isos
Tip
Remember to use a desktop profile stage3 for source_subpath when building a LiveGUI ISO.
Note
custom_livecd is used as the version_stamp here, but any unique build identifier can be used.

Adding custom packages

To add a package, such as app-misc/neofetch, it can be added to the livecd/packages list:

FILE /var/tmp/catalyst/installcd-stage1.specAdding netofetch to the livecd
livecd/packages:
	app-accessibility/brltty
	app-accessibility/espeakup
	app-admin/hddtemp
...
	sys-libs/glibc
	sys-libs/gpm
	sys-power/acpid
	www-client/links
	#Custom programs
	app-misc/neofetch

Build Stage1

With the stage1 spec configured, it can be built with:

/var/tmp/catalyst #catalyst -f installcd-stage1.spec

Stage2

The stage2 image is built using the stage1 as a base. This stage adds a kernel and bootloader, then wraps the root environment into a single bootable package.

Preparing the Stage2 Spec File

Similar to the stage1, several portions of the RelEng provided spec require edits:

  • version_stamp - The version string used for the catalyst build, can be set arbitrarily.
  • snapshot_treeish - The treeish for the portage snapshot.
  • source_subpath - The stage1 path, sourcing the stage3.
  • portage_confdir - The config dir for the build environment.
  • livecd/iso The filename for the output ISO.
  • livecd/volid The volume label for the output ISO.
  • boot/kernel/gentoo/config .config changed for the output kernel.
Important
Be sure to set the source_subpath to the path to the built stage 1, e.g. 23.0-default/custom_livecd.
FILE installcd-stage2-minimal.specLiveCD stage 2 base template.
subarch: amd64
version_stamp: @TIMESTAMP@
target: livecd-stage2
rel_type: 23.0-default
profile: default/linux/amd64/23.0/no-multilib
snapshot_treeish: @TREEISH@
source_subpath: 23.0-default/livecd-stage1-amd64-@TIMESTAMP@
portage_confdir: @REPO_DIR@/releases/portage/isos

livecd/bootargs: dokeymap
livecd/fstype: squashfs
livecd/iso: install-amd64-minimal-@TIMESTAMP@.iso
livecd/type: gentoo-release-minimal
livecd/volid: Gentoo-amd64-@DATESTAMP@

boot/kernel: gentoo

boot/kernel/gentoo/distkernel: yes
boot/kernel/gentoo/dracut_args: --xz --no-hostonly -a dmsquash-live -a mdraid -o btrfs -o crypt -o i18n -o usrmount -o lunmask -o qemu -o qemu-net -o nvdimm -o multipath -i /lib/keymaps /lib/keymaps -I busybox
boot/kernel/gentoo/config: @REPO_DIR@/releases/kconfig/amd64/dist-amd64-livecd.config
boot/kernel/gentoo/packages: net-wireless/broadcom-sta
FILE installcd-stage2-minimal.specLiveCD stage 2 filled template.
subarch: amd64
version_stamp: custom_livecd
target: livecd-stage2
rel_type: 23.0-default
profile: default/linux/amd64/23.0/no-multilib
snapshot_treeish: 3e5f2241174dbb89608c4766ca949e77cdca7b70
source_subpath: 23.0-default/livecd-stage1-amd64-custom_livecd
portage_confdir: /home/larry/gitstuff/releng/releases/portage/isos

livecd/bootargs: dokeymap
livecd/fstype: squashfs
livecd/iso: install-amd64-minimal-custom_livecd.iso
livecd/type: gentoo-release-minimal
livecd/volid: Gentoo-amd64-custom_livecd

boot/kernel: gentoo

boot/kernel/gentoo/distkernel: yes
boot/kernel/gentoo/dracut_args: --xz --no-hostonly -a dmsquash-live -a mdraid -o btrfs -o crypt -o i18n -o usrmount -o lunmask -o qemu -o qemu-net -o nvdimm -o multipath -i /lib/keymaps /lib/keymaps -I busybox
boot/kernel/gentoo/config: /home/larry/gitstuff/releng/releases/kconfig/amd64/dist-amd64-livecd.config
boot/kernel/gentoo/packages: net-wireless/broadcom-sta

Build Stage2

The ISO can be built with:

/var/tmp/catalyst #catalyst -f installcd-stage2-minimal.spec

ISO File

The ISO will be located in /var/tmp/catalyst/builds/default which can be written to a CD, USB or just tested directly in a VM.

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