---
title: "TOOCON - bootc, a kind of bootable container"
pubDatetime: 2024-11-05 20:20:00
slug: bootc
tags:
- meetup
- TOOCON
author: shawn
description: bootc, a kind of bootable container
hackmd: oBZXg0-RRyi86LZ1Y0S-_w

---
# bootc, a kind of bootable container

> 本頁為共筆 歡迎大家一起維護
> [](https://hackmd.io/oBZXg0-RRyi86LZ1Y0S-_w)

## bootc
bootc: Generating an ecosystem around bootable OCI containers
https://cfp.all-systems-go.io/all-systems-go-2024/talk/LA9LXV/

## live demo

* bootc status
* bootc switch
* centos stream to fedora
* systemcl status bootc-fetch-apply-updates

## What is bootable container?
- yes, container image as storage
- no, not a container or container engine; more like a deployer

## What is Container?

### An isolation Linux application.

- Open Container Initiative (oci)
- docker
- podman
- systemd-nspawn
- lxc

### Extensions
- kubernetes - CRI (Container runtime interface)
- containerd
- cri-o

## OCI Image
### registry - https://github.com/opencontainers/distribution-spec
- hub.docker.io
- quay.io
- ghcr.io
### image manifest / tar
- image
- list manifest
- type

### backend storage
layers, images, and containers

- docker
- overlay2 / fuse-overlayfs / btrfs and zfs / vfs
- podman / [containers/storage](https://github.com/containers/storage/)

## How it did?

----

Notes from 南部大聚

Note from Johnny Sung

https://www.facebook.com/share/p/129wP88YHmb/

ostree
https://github.com/ostreedev/ostree
Composefs
https://github.com/containers/composefs
怎麼用

mount -t composefs /path/to/image.cfs -o basedir=/path/to/datafiles /mnt

EROFS: Enhanced Read-Only File System
https://erofs.docs.kernel.org/en/latest/
bootc: Transactional, in-place operating system updates using OCI/Docker container images.
https://github.com/containers/bootc
Squashfs: compressed read-only filesystem for Linux
https://zh.m.wikipedia.org/zh-tw/SquashFS
https://docs.kernel.org/filesystems/squashfs.html
bootc image builder
https://docs.redhat.com/.../chap-anaconda-boot-options

---

# Immutable solutions

Upgrade system always is a pain point for me, especially with package manager systems.
They could work just sometime accident might happen, then need a lot of human operation to fix it.

There are lots of immutable solutions for os upgrade.

## solution concepts:
- A/B switch
- systemd usr-merge
- file system snapshot
- oci image

## solutions:
- ubuntu snap
- nixos
- talos
- bootc/ostree
- elemental-toolkit

## OCI ecosystem

- container engine - podman
- build / pull images

# bootc - bootable container

- ostree
- composefs

bootc as a bootable container runtime but it not really a runtime, more like a deployer.

https://github.com/containers/bootc

I really like bootc concept and thought it would the next `docker`.

## podman with composefs as storage backend

[Composefs state of the union](https://blogs.gnome.org/alexl/2023/07/11/composefs-state-of-the-union/)

https://github.com/containers/storage/pull/1646

https://github.com/containers/storage/blob/main/docs/containers-storage-composefs.md

containers-storage.conf /etc/containers/storage.conf

pull_options = {enable_partial_images = "true", use_hard_links = "true", ostree_repos="",  convert_images = "true"}

[storage.options.overlay]
use_composefs = "true"

[storage.options.pull_options]
convert_images = "true"

* [mount-cfs-oci.sh](/assets/mount-cfs-oci.sh)

#!/bin/bash

TAG=${TAG:=docker.io/library/alpine:latest} 
MNT=${MNT:=/mnt}

BASEDIR=/var/lib/containers/storage/overlay
INDEX_FN=$BASEDIR/../overlay-images/images.json


LAYER=$(cat ${INDEX_FN} | jq -r '.[] | select( .names |  any( "$TAG" ) )  | .layer')

mount -t composefs ${BASEDIR}/${LAYER}/composefs-data/composefs.blob -o basedir=${BASEDIR} $MNT

$ podman pull quay.io/centos-bootc/centos-bootc:stream9
$ podman image save quay.io/centos-bootc/centos-bootc:stream9 -o stream9.tar #(oci)

# podman image mount  quay.io/centos-bootc/centos-bootc:stream9
/var/lib/containers/storage/overlay/98cf94224120f2355d5efc4df25632f6789c3b251f52cc0893562f959d72a7f6/merged
# mkcomposefs /var/lib/containers/storage/overlay/98cf94224120f2355d5efc4df25632f6789c3b251f52cc0893562f959d72a7f6/merged --digest-store=/sysroot/composefs/repo /sysroot/composefs/images/bootc-cs9.cfs

# mount -o rw,remount /sysroot/
# initrd
#mount --bind /sysroot /sysroot.tmp

Containerfile `ln -s sysroot/composefs composefs`


mkdir /sysroot.tmp
mount /dev/vda3 /sysroot.tmp

mount -t composefs /sysroot.tmp/composefs/images/bootc-cs9.cfs -o basedir=/sysroot/composefs/repo /sysroot

mount --bind /sysroot.tmp/ostree/deploy/default/deploy/37595a2f96fc23131eef6af87920858e6eecc4de5540ef3278aa7e184c7d4d5c.0/etc /sysroot/etc
mount --bind /sysroot.tmp/ostree/deploy/default/var /sysroot/var

modprobe zram
modprobe xfs