From 434efcea2201ec30f0ccdb16322a598157e157f0 Mon Sep 17 00:00:00 2001 From: Breadway Date: Sat, 4 Jul 2026 19:00:15 +0800 Subject: [PATCH] Fix snapper create-config race: retry the whole dance, not just umount MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Confirmed on the test laptop's real install: /etc/snapper/configs/ was completely empty post-install — snapper create-config failed silently and BOS's advertised snapshot/rollback feature was entirely non-functional, despite snapper-cleanup.timer being enabled and grub-btrfsd active (both harmless no-ops with no config to act on). Root cause is the known chroot-specific busy-mount race already documented in this section's comments, but the existing recovery (retry umount 5x, then one lazy-unmount fallback) wasn't sufficient on this hardware — a lazy unmount detaches the mountpoint from the namespace immediately, but whatever was holding it busy can take a moment longer to actually release, and the immediately-following rmdir/create-config both fail if anything still references /.snapshots at that instant. Wrap the entire unmount → rmdir → create-config → cleanup → remount sequence in an outer retry loop (checking whether the config file actually exists before each attempt and after the loop), add a settle delay after the lazy-unmount fallback, and turn the final failure into a loud ERROR instead of a warning that's easy to miss — a system silently shipping without snapshots is worse than one that's slow to set them up. --- iso/airootfs/etc/calamares/post-install.sh | 60 ++++++++++++++-------- 1 file changed, 40 insertions(+), 20 deletions(-) diff --git a/iso/airootfs/etc/calamares/post-install.sh b/iso/airootfs/etc/calamares/post-install.sh index 9594719..025178e 100644 --- a/iso/airootfs/etc/calamares/post-install.sh +++ b/iso/airootfs/etc/calamares/post-install.sh @@ -272,30 +272,48 @@ fi # transiently fail inside the Calamares chroot (the same mount unmounts # cleanly moments later once booted normally — a chroot-specific busy-mount # race, not a logic error), which cascades into snapper create-config -# refusing because .snapshots "already exists". Retry a few times, then -# fall back to a lazy unmount (detaches the mountpoint immediately even if -# something still transiently references it) rather than give up. +# refusing because .snapshots "already exists". A single pass — retry the +# umount a few times, then fall back to a lazy unmount — was NOT enough on +# real hardware: also confirmed is a run where every umount attempt in that +# single pass failed (including the lazy fallback settling too slowly for +# the immediately-following rmdir/create-config), leaving +# /etc/snapper/configs/ completely empty and BOS's advertised snapshot/ +# rollback feature silently non-functional on that install. So retry the +# WHOLE dance, not just the umount substep, and verify at the end that the +# config file actually exists before declaring success. # --------------------------------------------------------------------------- if command -v snapper &>/dev/null; then - unmounted=0 - for _ in 1 2 3 4 5; do - if umount /.snapshots 2>/dev/null; then - unmounted=1 - break + for attempt in 1 2 3; do + [[ -f /etc/snapper/configs/root ]] && break + + unmounted=0 + for _ in 1 2 3 4 5; do + if umount /.snapshots 2>/dev/null; then + unmounted=1 + break + fi + sleep 1 + done + if [[ "$unmounted" != "1" ]]; then + echo "WARN: umount /.snapshots failed after retries (attempt $attempt), forcing lazy unmount" + umount -l /.snapshots || echo "WARN: lazy umount /.snapshots also failed (attempt $attempt)" + # Lazy unmount detaches the mountpoint from the namespace right + # away, but whatever was holding it busy may take a moment + # longer to actually let go — rmdir/create-config right after + # this both fail if anything still references /.snapshots. + sleep 2 fi - sleep 1 + rmdir /.snapshots 2>/dev/null || echo "WARN: rmdir /.snapshots failed (attempt $attempt)" + snapper -c root create-config / || echo "WARN: snapper create-config failed (attempt $attempt)" + if [[ -d /.snapshots ]]; then + btrfs subvolume delete /.snapshots || echo "WARN: deleting snapper's own .snapshots subvolume failed (attempt $attempt)" + fi + mkdir -p /.snapshots + mount /.snapshots || echo "WARN: remounting the real @snapshots subvolume failed (attempt $attempt)" + + [[ -f /etc/snapper/configs/root ]] || sleep 2 done - if [[ "$unmounted" != "1" ]]; then - echo "WARN: umount /.snapshots failed after retries, forcing lazy unmount" - umount -l /.snapshots || echo "WARN: lazy umount /.snapshots also failed" - fi - rmdir /.snapshots || echo "WARN: rmdir /.snapshots failed" - snapper -c root create-config / || echo "WARN: snapper create-config failed" - if [[ -d /.snapshots ]]; then - btrfs subvolume delete /.snapshots || echo "WARN: deleting snapper's own .snapshots subvolume failed" - fi - mkdir -p /.snapshots - mount /.snapshots || echo "WARN: remounting the real @snapshots subvolume failed" + if [[ -f /etc/snapper/configs/root ]]; then sed -i 's/TIMELINE_CREATE="yes"/TIMELINE_CREATE="no"/' /etc/snapper/configs/root sed -i 's/NUMBER_CLEANUP="no"/NUMBER_CLEANUP="yes"/' /etc/snapper/configs/root @@ -304,6 +322,8 @@ if command -v snapper &>/dev/null; then sed -i 's/NUMBER_LIMIT_IMPORTANT="[^"]*"/NUMBER_LIMIT_IMPORTANT="5"/' /etc/snapper/configs/root [[ -n "$MAIN_USER" ]] && \ sed -i "s/ALLOW_USERS=\"\"/ALLOW_USERS=\"$MAIN_USER\"/" /etc/snapper/configs/root + else + echo "ERROR: snapper config for root still missing after 3 attempts — snapshots/rollback will not work on this install" fi fi