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#!/bin/bash
#
# This script can be used as a workaround for systemd autofs mount migration.
# The problem is that systemd is a clever guy: before mounting of actual file
# system on top of autofs mount, it first checks that device number of autofs
# mount is equal to the one, stored in sytemd internals. If they do not match,
# systemd ignores kernel request.
# The problem happens each time autofs is restored (new device number for
# autofs superblock) and can't be properly solved without some kind of "device
# namespaces", where device number can be preseved.
# But some of systemd services can be painlessly restarted. Like
# proc-sys-fs-binfmt_misc.
#
# Usage:
# criu restore <options> --action-script $(pwd)/scripts/systemd-autofs-restart.sh
#
[ "$CRTOOLS_SCRIPT_ACTION" == "post-resume" ] || exit 0
if [ ! -n "$CRTOOLS_INIT_PID" ]; then
echo "CRTOOLS_INIT_PID environment variable is not set"
exit 1
fi
if [ ! -d "/proc/$CRTOOLS_INIT_PID" ]; then
echo "Process with CRTOOLS_INIT_PID=$CRTOOLS_INIT_PID doesn't exist"
exit 1
fi
NS_ENTER=/bin/nsenter
[ ! -x $NS_ENTER ] || NS_ENTER=/usr/bin/nsenter
if [ ! -x $NS_ENTER ]; then
echo "$NS_ENTER binary not found"
exit 2
fi
JOIN_CT="$NS_ENTER -t $CRTOOLS_INIT_PID -m -u -p"
# Skip container, if it's not systemd based
[ "$($JOIN_CT basename -- $($JOIN_CT readlink /proc/1/exe))" == "systemd" ] || exit 0
AUTOFS_SERVICES="proc-sys-fs-binfmt_misc.automount"
bindmount=""
function remove_bindmount {
if [ -n "$bindmount" ]; then
$JOIN_CT umount $bindmount
$JOIN_CT rm -rf $bindmount
bindmount=""
fi
}
trap remove_bindmount EXIT
function get_fs_type {
local mountpoint=$1
local top_mount_id=""
local top_mount_fs_type=""
while IFS='' read -r line; do
# Skip those entries which do not match the mountpoint
[ "$(echo $line | awk '{print $5;}')" = "$mountpoint" ] || continue
local mnt_id=$(echo $line | awk '{print $1;}')
local mnt_parent_id=$(echo $line | awk '{print $2;}')
local mnt_fs_type=$(echo $line | sed 's/.* - //g' | awk '{print $1;}')
# Skip mount entry, if not the first one and not a child
[ -n "$top_mount_id" ] && [ "$mnt_parent_id" != "$top_mount_id" ] && continue
top_mount_id=$mnt_id
top_mount_fs_type=$mnt_fs_type
done < "/proc/$CRTOOLS_INIT_PID/mountinfo"
if [ -z "$top_mount_fs_type" ]; then
echo "Failed to find $mountpoint mountpoint"
return 1
fi
echo $top_mount_fs_type
return 0
}
function bind_mount {
local from=$1
local to=$2
$JOIN_CT mount --bind $from $to && return 0
echo "Failed to bind mount $from to $to"
return 1
}
function save_mountpoint {
local mountpoint=$1
local top_mount_fs_type=""
top_mount_fs_type=$(get_fs_type $mountpoint)
if [ $? -ne 0 ]; then
echo "$top_mount_fs_type"
return
fi
# Nothing to do, if no file system is on top of autofs
[ "$top_mount_fs_type" = "autofs" ] && return
bindmount=$($JOIN_CT mktemp -d)
if [ -z "$bindmount" ]; then
echo "Failed to create temporary directory"
return 1
fi
# No need to unmount fs on top of autofs:
# systemd will does it for us on service restart
bind_mount $mountpoint $bindmount || $JOIN_CT rm -rf $bindmount
}
function restore_mountpoint {
local mountpoint=$1
[ -n "$bindmount" ] || return
# Umount file system, remounted by systemd, if any
top_mount_fs_type=$(get_fs_type $mountpoint)
if [ $? -ne 0 ]; then
echo "$top_mount_fs_type"
return
fi
# Nothing to do, if no file system is on top of autofs
if [ "$top_mount_fs_type" != "autofs" ]; then
$JOIN_CT umount $mountpoint || echo "Failed to umount $mountpoint"
fi
# Restore origin file system even if we failed to unmount the new one
bind_mount $bindmount $mountpoint
remove_bindmount
}
function restart_service {
local service=$1
local mountpoint=$($JOIN_CT systemctl show $service -p Where | sed 's/.*=//g')
if [ -z "$mountpoint" ]; then
echo "Failed to discover $service mountpoint"
return
fi
# Try to move restored bind-mount aside and exit if Failed
# Nothing to do, if we Failed
save_mountpoint $mountpoint || return
$JOIN_CT systemctl restart $service
if [ $? -ne 0 ]; then
echo "Failed to restart $service service"
return
fi
echo "$service restarted"
# Try to move saved monutpoint back on top of autofs
restore_mountpoint $mountpoint
}
for service in $AUTOFS_SERVICES; do
status=$($JOIN_CT systemctl is-active $service)
if [ $status == "active" ]; then
restart_service $service
else
echo "$service skipped ($status)"
fi
done
exit 0
|
