Run garbage collection on a bootc composefs backend repo using a forked cfsctl. WARN: EXPERIMENTAL, DO NOT USE IN PRODUCTION

bootc-cfsctl-cleanup

#!/bin/bash
# binary dependencies outside bootc, coreutils and util-linux: cfsctl jq
# use together with cfsctl from https://github.com/chaserhkj/composefs-rs (PR underway)
#
# This script cleans up bootc composefs repository, leaving only booted, stage and rollback deployments,
# pinning their images and streams running garbage collection on everything else, and finally removes
# unused BLS entires
set -e
shopt -s extglob nullglob

program=$(basename $0)

progress() {
    echo "($program) $@"
}

log_and_run() {
    echo "(running) $@"
    "$@"
}

dry_run() {
    echo "(dry run) $@"
}

[ "$(readlink /proc/self/ns/mnt)" = "$(readlink /proc/1/ns/mnt)" ] && { progress "Entering private mntns" ; exec unshare -m "$0" "$@"; }

run_prefix=dry_run
while [ $# -gt 0 ]; do
    if [ $1 = -f ] || [ $1 = --force ]; then
        run_prefix=log_and_run
    fi
    shift
done

bootc_status="$(bootc status --format json)"

for type in booted rollback staged; do
    printf -v "${type}_digest" "%s" $(echo "$bootc_status" | jq -r ".status.$type.image.imageDigest // \"\" " | cut -d: -f2)
    printf -v "${type}_verity" "%s" $(echo "$bootc_status" | jq -r ".status.$type.composefs.verity // \"\" ")
    printf -v "${type}_boot_digest" "%s" $(echo "$bootc_status" | jq -r ".status.$type.composefs.bootDigest // \"\" ")
    printf -v "${type}_boot_type"  "%s" $(echo "$bootc_status" | jq -r ".status.$type.composefs.bootType // \"\" ")
    printf -v "${type}_bootloader" "%s" $(echo "$bootc_status" | jq -r ".status.$type.composefs.bootloader // \"\" ")
done

progress "Resolved GC roots:"

for type in booted rollback staged; do
    for item in digest verity boot_digest boot_type bootloader; do
        var=${type}_${item}
        echo "  $var: ${!var}"
    done
    echo
done


efi_device=$(lsblk -o PATH -nr -Q 'PARTTYPE == "c12a7328-f81f-11d2-ba4b-00a0c93ec93b"')
gc_root_flags=

for type in booted rollback staged; do
    digest_var=${type}_digest
    [ -n "${!digest_var}" ] && gc_root_flags="$gc_root_flags -s oci-config-sha256:${!digest_var}"
    verity_var=${type}_verity
    [ -n "${!verity_var}" ] && gc_root_flags="$gc_root_flags -i ${!verity_var}"
done

progress "Remounting /sysroot RW"

$run_prefix mount --make-private /sysroot
$run_prefix mount -o remount,rw /sysroot

progress "Pruning /sysroot/state/deploy"

stale_deployments=( /sysroot/state/deploy/!($booted_verity|$rollback_verity|$staged_verity) )
$run_prefix rm -rf "${stale_deployments[@]}"

force_flag=
[ "$run_prefix" != "dry_run" ] && force_flag=--force

gc_log=/tmp/bootc-cfsctl-cleanup.gc.log
progress "Performing GC $force_flag on /sysroot/composefs and writing GC logs to $gc_log"

cfsctl_cmdline="RUST_LOG=debug cfsctl --repo /sysroot/composefs gc $gc_root_flags $force_flag >$gc_log 2>&1"
echo "(cfsctl) $cfsctl_cmdline"
eval "$cfsctl_cmdline"

echo "(cfsctl) Garbage collected objects: $(grep -E '(dry run: )?rm ' $gc_log | wc -l)"

clean_esp=yes
for type in booted rollback staged; do
    var=${type}_boot_type
    # when boot_type is empty string, assume the current entry is empty and skip to next entry
    [ -z "${!var}" ] && continue
    [ "${!var}" != "Bls" ] && clean_esp=no
    var=${type}_bootloader
    [ "${!var}" != "Systemd" ] && clean_esp=no
done

if [ "$clean_esp" != "yes" ]; then
    progress "Unsupported bootloader/boot type is used, skip cleaning ESP"
    exit 0
fi

progress "Mounting ESP"

log_and_run mount --make-private $efi_device /sysroot/boot
boot_contents=( /sysroot/boot/EFI/Linux/* )

progress "Cleaning unused kernel files"

# /sysroot/boot/EFI/Linux entires may still refer to stale deployment ids
# Try to rename them to current deployment ids
# This is necessary to make "bootc upgrade" and "bootc switch" function correctly
stale_deployment_ids=()
for path in "${stale_deployments[@]}"; do
    stale_deployment_ids+=( "$(basename $path)" )
done

declare -A rename_map

for boot_content_dir in "${boot_contents[@]}"; do
    boot_content_id=$(basename $boot_content_dir)
    used=no
    boot_digest=$(cat $boot_content_dir/vmlinuz $boot_content_dir/initrd | sha256sum | cut -d" " -f1)
    echo "(ESP GC) Boot binary entry: $boot_content_id"
    echo "(ESP GC) Boot binary digest: $boot_digest"
    # This order decides which digest to use for rename when multiple entries share same boot binaries
    # Always prioritize staged > booted > rollback
    for entry_type in rollback booted staged; do

        digest_var_name=${entry_type}_boot_digest
        match_digest=${!digest_var_name}
        

        if [[ "$boot_digest" == "$match_digest" ]]; then
            used=yes
        else
            continue
        fi

        verity_var_name=${entry_type}_verity
        match_verity=${!verity_var_name}

        # Check if used boot binary is referring to stale deployment id
        for stale_id in "${stale_deployment_ids[@]}"; do
            [[ "$stale_id" != "$boot_content_id" ]] && continue
            rename_map[$stale_id]=$match_verity
            echo "  mark rename, from $stale_id"
            echo "  to $match_verity"
        done
    done
    [ "$used" != "yes" ] && $run_prefix rm -rf $boot_content_dir
done

progress "Renaming ESP references to stale entries"

for from in "${!rename_map[@]}"; do
    to=${rename_map[$from]}
    $run_prefix mv /sysroot/boot/EFI/Linux/$from /sysroot/boot/EFI/Linux/$to
    $run_prefix sed -i "s/\\/$from\\//\\/$to\\//g" /sysroot/boot/loader/entries/*.conf
done