#!/bin/sh
if [ $PPID -eq 1 ]; then
# This code snippet runs inside of the initramfs, right after the kernel
# has mounted the ZFS root file system.
# If there is a file telling us that a rollback was previously requested,
# attempt to do so now.
# N.B.: This code runs in a BusyBox environment. Don't expect to get all of
# the same powerful commands that a full Linux system has access to. Tread
# with care when writing shell scripts.
if [ -r "${rootmnt}/.rollback-zfs" ]; then
rollback() {
local label="$1"
# We only ever attempt to roll back the root filesystem, as it is the only
# one that is a little tricky to do. Snapshots for other mountpoints
# should be handled with the tools that Linux and/or PVE provide for this
# purpose.
local root="$(awk "/ ${rootmnt////\\/} zfs /"'{ print $1 }' /proc/mounts)"
# While ZFS has the option to roll back multiple generations of snapshots,
# we aim to be conservative and will only ever roll back the most recent
# snapshot. If you need to roll back to an earlier snapshot, you should
# explicitly destroy the ones that you no longer need.
local snapshots="$(zfs list -t snapshot "${root}" 2>/dev/null |
awk "/^${root////\\/}/"'{ print $1 }')"
local last="$(echo "${snapshots}" | sed -n 's/[^@]*@//;$p')"
[ -n "${last}" -a "x${last}" = "x${label}" ] || return
# Remove the file telling us to perform a rollback operation. This should
# help avoid boot loops if the rollback is not successful.
rm -f "${rootmnt}/.rollback-zfs"
zfs rollback "${root}@${label}" || :
}
rollback "$(cat "${rootmnt}/.rollback-zfs")"
# Again, remove the file telling us to perform rollbacks. This prevents
# nasty surprises if this file made it into the snapshot.
rm -f "${rootmnt}/.rollback-zfs"
fi
elif [ "x$*" = "xprereqs" ]; then
# Our script can get invoked for several different reasons; one of them
# would be when the initramfs gets assembled. Don't do anything in that
# case.
exit 0
else
# This is our entry-point into this script, when a user invokes us to
# manage their snapshots. Perform the required sanity checking and print
# appropriate messages.
usage() {
echo "${0##*/}: [--cancel] <snapshot>" >&2
}
# Check for root permissions
[ "$(id -u)" = 0 ] || { echo "Must run as root user" >&2; exit 1; }
[ $# = 1 ] || { usage; exit 1; }
# If invoked with the "--cancel" option, delete the file that controls
# rollbacks.
if [ "x$1" = "x--cancel" ]; then
rm -f /.rollback-zfs
exit 0
fi
# Sanity check that the caller is asking us to remove the most recent
# snapshot. This information can of course still change several times
# before the system has actually rebooted, and we will double-check again
# before performing the actual rollback. But an early check at this
# place allows us to print helpful messages to the user.
root="$(awk "/ \/ zfs /"'{ print $1 }' /proc/mounts)"
[ -n "${root}" ] || {
echo "Cannot find a root ZFS filesystem" >&2
exit 1
}
r_="$(echo "${root}" | sed 's,/,\/,g')"
snapshots="$(zfs list -t snapshot "${root}" 2>/dev/null |
awk "/^${r}/"'{ print $1 }')"
echo "${snapshots}" | egrep @"$1"'([[:space:]]|$)' >/dev/null 2>&1 || {
echo "Root filesystem on ${root} does not have a snapshot called $1" >&2
exit 1
}
last="$(echo "${snapshots}" | sed -n 's/[^@]*@//;$p')"
[ "x$1" = "x${last}" ] || {
echo "Will only roll back to most recent snapshot. Delete any uneeded" >&2
echo "snapshots, if you want to roll back to an older one instead." >&2
exit 1
}
# Make sure our script is part of the initramfs for the current kernel.
if ! [ -r /usr/share/initramfs-tools/scripts/local-bottom/rollback-zfs ] ||
! cmp "$0" /usr/share/initramfs-tools/scripts/local-bottom/rollback-zfs \
>/dev/null 2>&1; then
cp "$0" /usr/share/initramfs-tools/scripts/local-bottom/rollback-zfs
update-initramfs -u
# proxmox-boot-tool refresh
echo
fi
# Explain the next steps that the user needs to take.
echo "$1" >/.rollback-zfs
cat <<EOF
The system will roll back to "$1" upon the next reboot.
You must initiate this reboot yourself (e.g. by running "/usr/sbin/reboot").
After the system has booted again, the snapshot will NOT be removed
automatically. If you no longer need it, you must execute
"zfs destroy ${root}@$1" yourself.
EOF
fi
