scripts to initiate a backup from a source Synology NAS

do_backup.sh

#!/bin/sh
# this script will initiate a backup from a source Synology NAS
# 'challenges'
# - there's no blocking means to run a backup task (i.e. a command to start a
#   backup task and not return until it's complete); instead we only have
#   asynchronous actions to start a task and then later check state
# - it takes some period of time to actually start the task, i.e. starting a
#   backup and immediately checking backup state will likely (incorrectly)
#   return "not running"
# - there appears to be no way to actually tell if the backup succeeded or not,
#   other than inspecting the log file (sigh)
#   - root (sudo) is required to read journal logs; the user this script runs as
#     needs to be in the `wheel` group so as to be able to sudo without a password
#     (ref. /etc/sudoers), e.g. for the user `offsite`:
#     synogroup --memberadd wheel offsite
#     (will also need to be in `administrators` in order to ssh)
#
# - the synobackup utility requires the 'task id', however there is no simple
#   way of determining the task ID for a task created via the UI
#   - prior to Hyperbackup 4.1.0 the task ID was listed in
#     /usr/syno/etc/synobackup.conf ('ini' format, unparseable)
#     however that file no longer exists and the task ID appears to be
#     indeterminable.
#     - fortunately it appears to be simply an index starting from 1,
#       incremented whenever a new task is created; moreover passing an invalid
#       task id appears to have no harm
#       i.e. invoke synobackup with a task ID of 1, increment until you see
#       (in the UI) the job you want to run actually start

TASK_ID="$1"

HOSTNAME="$(hostname)"

log () {
  echo "$(date) [${HOSTNAME}] $*"
}

if [ $# -eq 0 ]; then
  echo "usage: $0 <task id>" >&2
  exit 1
fi

# synobackup does not provide any means to check whether a backup worked (e.g.
# result of last backup); have to resort to monitoring the log...
# examples:
# - partial failure (source folder not mounted):
# Jan 20 10:28:19 bd synobackupd[6784]: launch job [3] on pid [23763]
# Jan 20 10:56:24 bd img_backup[23763]: (23763) [err] backup_progress.cpp:501 Backup task [offsite - general] completes with result [2] and errorcode [3004]. Time spent: [1684 sec].
# - success
# Jan 20 10:58:39 bd synobackupd[6784]: launch job [4] on pid [28621]
# Jan 20 11:00:54 bd img_backup[28621]: (28621) [err] backup_progress.cpp:504 Backup task [offsite - photo] completes with result [1]. Time spent: [132 sec].


# - don't want the whole log, only what's added during our run
now=$(date +%s)

getsynolog () {
  sudo journalctl --no-pager --unit synobackupd.service --since "@$now"
}

_exit() {
  log "exiting"
  getsynolog | grep --quiet --fixed-strings 'completes with result [1]'
  rc=$?
  if [ $rc -ne 0 ]; then
    log "failed?"
  fi

  log "synobackupd log:"
  getsynolog
  exit "$rc"
}
trap _exit EXIT

# no sudo, plain ol' admins can kick off a backup...
/usr/syno/bin/synobackup --backup "${TASK_ID}" --type image
case $? in
  0)
    log "backup task ID ${TASK_ID} started"
	;;
  153)
    log "backup task  ID ${TASK_ID} already running?"
    exit 1
    ;;
  *)
    log "failed to start backup task  ID ${TASK_ID}"
    exit 1
    ;;
esac

is_backup_running() {
  # synobackup's exit status is backwards:
  #   0 (i.e. success/true) if not running
  #   1 (i.e. error/false) if running
  if /usr/syno/bin/synobackup --is-backup-restore-running; then
    return 1
  fi
  return 0
}

# can take a moment before synobackup reports the task state, so sleep up front
# "give up" logic: things don't always go to plan:
#   - wait till the backup ends; increasing intervals, to a total of ~30 hrs
for s in $(seq 90 15 1800) -1; do 
  if [ "${s}" -lt 0 ]; then
    log "timed out: backup still running??"
    exit 2
  fi
  log "waiting ${s}s"
  sleep "$s"
  if ! is_backup_running; then
    log "backup finished running"
    break
  fi
done

pull_backup.sh

#!/bin/sh
# this script will initiate a backup from a source Synology NAS
# - before deploying this script via the Synology task scheduler: the backup
#   source's ssh host key needs to be recorded in ~/.ssh/known_hosts - to do
#   so, as the user that will run this script in the Synology task scheduler,
#   invoke this script with only the user@host argument, e.g.
#   sudo ./pull_backup.sh [email protected]
# - if running via the 'Boot-up' Task Scheduler event it will be beneficial to precede
#   invocation of this script with a `sleep 180` otherwise you may get spurious
#   networking errors
# - this script needs to be run as root so as to be able to call shutdown
# - invoke with arg1 as target username@host; arg2 as the backup script on the target
#   - in turn, the backup script requires the synobackup task ID
#   e.g.
#   sudo $0 [email protected] ./do_backup.sh 3

HOSTNAME="$(hostname)"

log () {
  echo "$(date) [${HOSTNAME}] $*"
}


ssh_with_args() {
  # adjust as needed
  ssh "$SSH_TARGET" \
    -o ControlMaster=auto -o ControlPersist=5m -o ControlPath=~/.ssh/cm-%r@%h:%p \
    "$@"
}

if [ $# -eq 0 ]; then
  echo "usage: $0 user@host dobackup_script [dobackup_script args]" >&2
  exit 1
fi

SSH_TARGET="$1"
shift

# if invoked with just one argument, do a "ssh host key scan" and exit
# note: synology doesn't provide ssh-keyscan...
if [ $# -eq 0 ]; then
  ssh_with_args -o StrictHostKeyChecking=no exit
  exit
fi

# shutdown will be suppressed if, when the backup ends:
# - anyone is logged in via ssh
# - this file is present:
NOSHUTDOWN="$0.noshutdown"

do_shutdown() {
  # return true if shutdown should proceed
  [  -e "${NOSHUTDOWN}" ] && return 1
  who --short | grep -q '.' && return 1
  return 0
}

# can take a moment for ssh to get going (e.g. VPN/tunnel to establish)
for s in $(seq 30 15 90) -1; do
  if [ "${s}" -lt 0 ]; then
    log "failed to connect to $SSH_TARGET"
    exit 1
  fi
  if ssh_with_args true; then
    log "connected to $SSH_TARGET"
    break
  fi
  log "waiting to connect"
  sleep "$s"
done

log "executing $@"
if ! ssh_with_args "$@"; then
  log "failed"
  exit 1
fi

log "success"
# shutdown ignores arguments; certainly time; so DIY
# this is important: need to provide opportunity to fix things
if do_shutdown; then
  log "shutting down"
  # leave the pending shutdown run in the background, so as to let any email report/etc go out
  nohup sh -c 'sleep 300 && shutdown --poweroff' >/dev/null &
fi