iankelling.org Git - distro-setup/blob - btrbk-run

   1 #!/bin/bash
   2 # Copyright (C) 2016 Ian Kelling
   3
   4 # Licensed under the Apache License, Version 2.0 (the "License");
   5 # you may not use this file except in compliance with the License.
   6 # You may obtain a copy of the License at
   7
   8 #     http://www.apache.org/licenses/LICENSE-2.0
   9
  10 # Unless required by applicable law or agreed to in writing, software
  11 # distributed under the License is distributed on an "AS IS" BASIS,
  12 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13 # See the License for the specific language governing permissions and
  14 # limitations under the License.
  15
  16
  17 # todo: if we cancel in the middle of a btrfs send, then run again
  18 # immediately, the received subvolume doesn't get a Received UUID:
  19 # field, and we won't mount it. Need to figure out a solution that will
  20 # fix this.
  21
  22
  23 [[ $EUID == 0 ]] || exec sudo -E "${BASH_SOURCE[0]}" "$@"
  24
  25 source /usr/local/lib/err
  26
  27 usage() {
  28   cat <<'EOF'
  29 btrbk-run [OPTIONS] [run|resume|archive]
  30 usually -t TARGET_HOST or -s SOURCE_HOST
  31
  32 Note, at source location, intentionally not executable, run and read
  33 install-my-scripts.
  34
  35 EOF
  36   echo "top of script file:"
  37   sed -n '1,/^[# ]*end command line/{p;b};q' "$0"
  38   exit $1
  39 }
  40
  41
  42
  43 script_name="${BASH_SOURCE[0]}"
  44 script_name="${script_name##*/}"
  45 pre="${SSH_CLIENT:+$HOSTNAME} $script_name:"
  46 m() { if $verbose; then printf "$pre%s\n"  "$*"; fi;  "$@"; }
  47 e() { printf "$pre%s\n"  "$*"; }
  48 die() { printf "$pre%s\n" "$*" >&2; echo "exiting with status 1" >&2; exit 1; }
  49 mexit() { echo "$pre: exiting with status $1"; exit $1; }
  50
  51 # latest $MAIL_HOST
  52 if [[ -e /b/bash_unpublished/source-state ]]; then
  53   source /b/bash_unpublished/source-state
  54 fi
  55
  56 # note q is owned by root:1000
  57
  58 mountpoints=()
  59
  60 rsync_mountpoint=/q
  61
  62 ret=0
  63 # default options
  64 conf_only=false
  65 dry_run=false # mostly for testing
  66 rate_limit=no
  67 verbose=true; verbose_arg=-v
  68 if [[ $INVOCATION_ID ]]; then
  69   # INVOCATION_ID means running as a systemd service. we cant show progress in this case,
  70   # but if we pass the arg, it will insert mbuffer into the command.
  71   progress_arg=
  72 else
  73   progress_arg="--progress"
  74 fi
  75 incremental_strict=false
  76 pull_reexec=false
  77
  78 default_args_file=/etc/btrbk-run.conf
  79 if [[ -s $default_args_file ]]; then
  80   # shellcheck disable=SC2046 # we want word splitting
  81   set -- $(< $default_args_file) "$@"
  82   # i havent used this feature yet, so warn about it
  83   echo "$0: warning: default btrbk-run options set in $default_args_file (sleeping 5 seconds):"
  84   cat $default_args_file
  85   sleep 5
  86 fi
  87
  88 targets=()
  89 early=false
  90 cron=false
  91 fast=false
  92 orig_args=("$@")
  93 temp=$(getopt -l cron,fast,pull-reexec,help 23ceil:m:npqrs:t:vh "$@") || usage 1
  94 eval set -- "$temp"
  95 while true; do
  96   case $1 in
  97     # some behaviors specific to running under cron:
  98     # - skip hosts where xprintidle haven't been idle recently
  99     # - if we can't ssh to 1 or more hosts, still do the rest
 100     # - if we aren't MAIL_HOST and no -m or -s, just exit
 101     --cron)
 102       cron=true
 103       pre=
 104       ;;
 105     # for the rare case we want to run multiple instances at the same time
 106     -2) conf_suf=2 ;;
 107     -3) conf_suf=3 ;;
 108     # only creates the config file, does not run btrbk
 109     -c) conf_only=true ;;
 110     # quit early, just btrbk, no extra remounting etc.
 111     -e) early=true ;;
 112     # skip various checks. when we run twice in a row for
 113     # switch mail-host, no need to repeat the same checks again.
 114     --fast) fast=true ;;
 115     -i) incremental_strict=true ;;
 116     # bytes per second, suffix k m g
 117     -l) rate_limit=$2; shift ;;
 118     # Comma separated mountpoints to backup. This has defaults set below.
 119     -m) IFS=, mountpoints=($2); unset IFS; shift ;;
 120     -n) dry_run=true ;;
 121     # hide progress
 122     -p) progress_arg= ;;
 123     # internal option for rerunning under newer SOURCE_HOST version.
 124     --pull-reexec) pull_reexec=true;;
 125     # quiet
 126     -q) verbose=false; verbose_arg=; progress_arg= ;;
 127     # source host to receive a backup from
 128     -s)
 129       source=$2
 130       bbksource=$source
 131       if [[ $source == *:* ]]; then
 132         bbksource="[$source]"
 133       fi
 134       shift
 135       ;;
 136     # target hosts to send to. empty is valid for just doing local
 137     # snapshot. we have default hosts we will populate.
 138     -t) IFS=, targets=($2); unset IFS; shift ;;
 139     # verbose.
 140     -v) verbose=true; verbose_arg=-v ;;
 141     -h|--help) usage ;;
 142     --) shift; break ;;
 143     *) die "Internal error!" ;;
 144   esac
 145   shift
 146 done
 147
 148 cmd_arg=${1:-run}
 149
 150
 151 std_preserve="36h 14d 8w 24m"
 152 q_preserve="18h 14d 8w"
 153
 154 case $cmd_arg in
 155   run|resume) : ;;
 156
 157   # This works better than the normal archive command. We have to
 158   # specify the mount points, but that is what we are used to doing and
 159   # we prefer it. Another difference is that archive works recursively
 160   # and we don't care about that. Sometimes we may still want to run
 161   # btrbk archive, but it doesn't even use the config file, so just
 162   # run it directly, eg:
 163   # time s btrbk -v archive /mnt/r7/amy/boot/btrbk ssh://bo/mnt/boot2/btrbk
 164   archive)
 165     cmd_arg=resume
 166     std_preserve="999h 999d 999w 999m"
 167     q_preserve="$std_preserve"
 168     preserve_arg=-p
 169     ;;
 170   *) die "untested command arg" ;;
 171 esac
 172
 173 if (( $# > 1 )); then
 174   die: "only 1 nonoption arg is supported"
 175 fi
 176
 177 if [[ -v targets && $source ]]; then
 178   # note, this doesnt need to be the case, but
 179   # we would need to think about it.
 180   die "error: -t and -s are mutually exclusive"
 181 fi
 182
 183 if $verbose; then
 184   printf "$pre options: conf_only=%s\ndry_run=%s\nrate_limit=%s\nverbose=%s\ncmd_arg=%s" "$conf_only" "$dry_run" "$rate_limit" "$verbose" "$cmd_arg"
 185 fi
 186 ### end options parsing
 187
 188 # remove path from earlier version of btrbk
 189 rm -f /usr/sbin/btrbk
 190 # note, this still works as intended if there is no /usr/bin/btrbk
 191 if [[ /a/opt/btrbk/btrbk -nt /usr/bin/btrbk ]]; then
 192   if [[ -e /b/distro-functions/src/package-manager-abstractions ]]; then
 193     . /b/distro-functions/src/package-manager-abstractions
 194     pi asciidoctor
 195   fi
 196   cd /a/opt/btrbk
 197   m make install
 198 fi
 199
 200 # TODO: i wonder if there should be an option to send to the default
 201 # targets, plus any given on the command line.
 202
 203
 204
 205 kd_spread=false
 206 # set default targets
 207 if [[ ! -v targets && ! $source ]]; then
 208   if $cron; then
 209     if [[ $HOSTNAME != "$MAIL_HOST" ]]; then
 210       if [[ $HOSTNAME == kd && $MAIL_HOST == x3 ]]; then
 211         if ping -q -c1 -w1 x3.office.fsf.org &>/dev/null; then
 212           work_host=x3.office.fsf.org
 213         elif ping -q -c1 -w1 x3wg.b8.nz &>/dev/null; then
 214           work_host=x3wg.b8.nz
 215         fi
 216         if [[ $work_host ]]; then
 217           source_state="$(ssh $work_host cat /a/bin/bash_unpublished/source-state)"
 218           eval "$source_state"
 219           if [[ $MAIL_HOST == x3 ]]; then
 220             kd_spread=true
 221           else
 222             echo "MAIL_HOST=$MAIL_HOST, nothing to do"
 223             mexit 0
 224           fi
 225         else
 226           echo "MAIL_HOST=$MAIL_HOST, nothing to do"
 227           mexit 0
 228         fi
 229       else
 230         echo "MAIL_HOST=$MAIL_HOST, nothing to do"
 231         mexit 0
 232       fi
 233     fi
 234   fi
 235
 236   at_work=false
 237   at_home=false
 238
 239   case $HOSTNAME in
 240     kw|kd|frodo|x2|x3|sy) : ;;
 241     *)
 242       die "error: no default targets for this host, use -t"
 243       ;;
 244   esac
 245
 246   case $HOSTNAME in
 247     kw)
 248       at_work=true
 249       ;;&
 250     kd|frodo)
 251       at_home=true
 252       ;;&
 253     x2|x3|sy)
 254       if [[ $(dig +short @10.2.0.1 -x 10.2.0.2 2>&1 ||:) == kd.b8.nz. ]] \
 255            && ip n show 10.2.0.1 | grep . &>/dev/null; then
 256         at_home=true
 257       elif ping -q -c1 -w1 hal.office.fsf.org &>/dev/null \
 258           && ip n show 192.168.0.26 | grep . &>/dev/null; then
 259         at_work=true
 260       fi
 261       ;;&
 262     *)
 263       if $at_home; then
 264         if ! $kd_spread; then
 265           # main work machine
 266           if ping -q -c1 -w1 x3.office.fsf.org &>/dev/null; then
 267             targets+=(x3.office.fsf.org)
 268           else
 269             targets+=(x3wg.b8.nz)
 270           fi
 271         fi
 272         # temporarily disabled while doing recovery
 273 #        for h in frodo kd; do
 274         for h in kd; do
 275           if [[ $HOSTNAME == "$h" ]]; then
 276             continue
 277           fi
 278           targets+=($h.b8.nz)
 279         done
 280         for h in x2 x3 sy; do
 281           if [[ $HOSTNAME == "$h" ]]; then
 282             continue
 283           fi
 284           if ping -q -c1 -w1 $h.b8.nz &>/dev/null; then
 285             targets+=($h.b8.nz)
 286           elif ping -q -c1 -w1 ${h}w.b8.nz &>/dev/null; then
 287             targets+=(${h}w.b8.nz)
 288           fi
 289         done
 290       elif $at_work; then
 291         if ping -q -c1 -w1 iank.vpn.office.fsf.org &>/dev/null; then
 292           targets+=(iank.vpn.office.fsf.org)
 293         else
 294           targets+=(i.b8.nz)
 295         fi
 296         for h in x2 x3 kw; do
 297           if [[ $HOSTNAME == "$h" ]]; then
 298             continue
 299           fi
 300           if ping -q -c1 -w1 $h.office.fsf.org &>/dev/null; then
 301             targets+=($h.office.fsf.org)
 302           fi
 303         done
 304       else
 305         targets+=(i.b8.nz)
 306       fi
 307       ;;
 308   esac
 309 fi
 310
 311 if [[ -v targets ]]; then
 312   echo "targets: ${targets[*]}"
 313 fi
 314
 315 if [[ $source ]]; then
 316   echo "source: $source"
 317 fi
 318
 319 if [[ ${mountpoints[0]} ]]; then
 320   for mp in ${mountpoints[@]}; do
 321     if [[ -e /nocow/btrfs-stale/$mp ]]; then
 322       die "error: $mp is stale, mount-latest-subvol first"
 323     fi
 324   done
 325 else
 326   # set default mountpoints
 327   if [[ ${targets[0]} == tp ]]; then
 328     prospective_mps=(/a)
 329   else
 330     case $HOSTNAME in
 331       *)
 332         prospective_mps=()
 333         if [[ $source ]]; then
 334           source_state="$(ssh $source cat /a/bin/bash_unpublished/source-state)"
 335           eval "$source_state"
 336           source_host="$(ssh $source cat /etc/hostname)"
 337           if [[ $source_host == "$MAIL_HOST" ]]; then
 338             prospective_mps+=(/o)
 339           fi
 340           if [[ $source_host == "$HOST2" ]]; then
 341             prospective_mps+=(/a /ar /qr /q)
 342           fi
 343         else
 344           if [[ $HOSTNAME == "$MAIL_HOST" ]]; then
 345             prospective_mps+=(/o)
 346           fi
 347           if [[ $HOSTNAME == "$HOST2" ]]; then
 348             prospective_mps+=(/a /ar /qr /q)
 349           fi
 350         fi
 351         # note: put q last just in case its specific retention options were to
 352         # affect other config sections. I havent tested if that is the case.
 353         ;;
 354     esac
 355   fi
 356   for mp in ${prospective_mps[@]}; do # default mountpoints to sync
 357     if [[ -e /nocow/btrfs-stale/$mp ]]; then
 358       e "warning: $mp stale, not adding to default mountpoints"
 359       continue
 360     fi
 361     if awk '{print $2}' /etc/fstab | grep -xF $mp &>/dev/null; then
 362       mountpoints+=($mp)
 363     fi
 364   done
 365 fi
 366
 367 echo "mountpoints: ${mountpoints[*]}"
 368
 369 ##### end command line parsing ########
 370
 371 # todo: this has a timing problem, since btrbk.timer could activate the service after this check.
 372 if ! $fast && [[ $source ]]; then
 373   if [[ $(ssh $source ps --no-headers -o comm 1) == systemd ]]; then
 374     status=$(ssh $source systemctl is-active btrbk.service) || : # normally returns 3
 375     case $status in
 376       inactive|failed) : ;;
 377       *)
 378         echo "$0: error: cron btrbk is running on source. exiting out of caution"
 379         mexit 1
 380     esac
 381   fi
 382 fi
 383
 384 # pull_reexec stops us from getting into an infinite loop if there is some
 385 # kind of weird problem
 386 pulla=false
 387 for m in "${mountpoints[@]}"; do
 388   if [[ $m == /a ]]; then
 389     pulla=true
 390     break
 391   fi
 392 done
 393 if ! $pull_reexec && [[ $source ]] && $pulla ; then
 394   tmpf=$(mktemp)
 395   m rsync -ra $source:/usr/local/bin/{mount-latest-subvol,check-subvol-stale} /usr/local/bin
 396   m rsync -ra $source:/usr/local/lib/err /usr/local/lib
 397   m scp $source:/a/bin/distro-setup/btrbk-run $tmpf
 398   if ! diff -q $tmpf ${BASH_SOURCE[0]}; then
 399     e "found different version on host $source. reexecing"
 400     install -T $tmpf /usr/local/bin/btrbk-run
 401     m /usr/local/bin/btrbk-run --pull-reexec "${orig_args[@]}"
 402     mexit 0
 403   fi
 404 fi
 405
 406
 407 if ! command -v btrbk &>/dev/null; then
 408   die "error: no btrbk binary found"
 409 fi
 410
 411 if ! $fast; then
 412   # if our mountpoints are from stale snapshots,
 413   # it doesn't make sense to do a backup.
 414   m check-subvol-stale ${mountpoints[@]} || die "found stale mountpoints in ${mountpoints[*]}"
 415
 416   # for an initial run, btrbk requires the dir to exist.
 417   mkdir -p /mnt/{root,o}/btrbk
 418 fi
 419 local_zone=$(date +%z)
 420
 421 if [[ $source ]]; then
 422   if $fast; then
 423     zone=$local_zone
 424   else
 425     if ! zone=$(ssh root@$source date +%z); then
 426       if $conf_only; then
 427         echo "$0: warning: failed to ssh to root@$source"
 428       else
 429         die failed to ssh to root@$source
 430       fi
 431     fi
 432     if [[ $zone != "$local_zone" ]]; then
 433       die "error: dont confuse yourself with multiple time zones. $h has different timezone than localhost"
 434     fi
 435   fi
 436 else
 437
 438   sshable=()
 439   sshfail=()
 440   min_idle_ms=$((1000 * 60 * 15))
 441   for h in ${targets[@]}; do
 442     if $fast || $conf_only; then
 443       # Use some typical values in this case
 444       root_size=$(( 1024 * 1024 * 2000 )) #2tb
 445       percent_used=10
 446       zone=$(date +%z)
 447     elif remote_str=$(timeout -s 9 6 ssh root@$h "mkdir -p /mnt/root/btrbk /mnt/o/btrbk && date +%z && df --output=size,pcent / | tail -n1"); then
 448       mapfile -t tmp_array <<<"$remote_str"
 449       zone="${tmp_array[0]}"
 450       IFS=" " read -r root_size percent_used <<<"${tmp_array[1]}"
 451       percent_used=${percent_used%%%}
 452
 453       if (( ${#tmp_array[@]} != 2 )); then
 454         die "error: didnt get 2 lines in test ssh to target $h. investigate"
 455       fi
 456       case $percent_used in
 457         [0-9]|[1-9][0-9]) : ;;
 458         *)
 459           die "error: didnt get percent disk use in test ssh to target $h. investigate"
 460           ;;
 461       esac
 462     else
 463       sshfail+=($h)
 464       continue
 465     fi
 466
 467     # we may be booted into a bootstrap fs or something
 468     min_root_kb=$(( 1024 * 1024 * 200 )) # 200 gb
 469     if (( root_size < min_root_kb )); then
 470       continue
 471     fi
 472
 473     if (( percent_used >= 98 )); then
 474       die "error: filesystem on target $h is $percent_used % full"
 475     fi
 476
 477     # This is a separate ssh because xprintidle can fail and thats ok.
 478     if $cron && idle_ms=$(timeout -s 9 6 ssh $h DISPLAY=:0 xprintidle); then
 479       if (( idle_ms < min_idle_ms )); then
 480
 481         # Ignore this host. i sometimes use a non-main machine for
 482         # testing or web browsing, knowing that everything will be wiped
 483         # by the next backup, but I dont want it to happen as Im using
 484         # it from cronjob.
 485         e "warning: $h: active X session in the last 15 minutes, skipping for now"
 486         continue
 487       fi
 488     fi
 489     sshable+=($h)
 490     if [[ $zone != "$local_zone" ]]; then
 491       die "error: dont confuse yourself with multiple time zones. $h has different timezone than localhost"
 492     fi
 493   done
 494   if [[ ! ${sshable[*]} ]] || { ! $cron && [[ ${sshfail[*]} ]]; }; then
 495     die "failed to ssh to hosts: ${sshfail[*]}"
 496   else
 497     if [[ ${sshfail[*]} ]]; then
 498       ret=1
 499       e "error: failed to ssh to ${sshfail[*]} but continuing with other hosts"
 500     fi
 501     targets=(${sshable[@]})
 502   fi
 503 fi
 504
 505
 506 cat >/etc/btrbk$conf_suf.conf <<EOF
 507 ssh_identity /q/root/h
 508 #ssh_identity /root/.ssh/home
 509
 510 # Just a guess that local7 is a good facility to pick.
 511 # It's a bit odd that the transaction log has to be logged to
 512 # a file or syslog, while other output is sent to std out.
 513 # The man does not mention a way for them to be together, but
 514 # I dunno if setting a log level like warn might also output
 515 # transaction info.
 516 transaction_syslog local7
 517
 518 # trying this out
 519 #stream_compress zstd
 520
 521 # so we only run one at a time
 522 lockfile                   /var/lock/btrbk$conf_suf.lock
 523
 524 # default format of short does not accomidate hourly preservation setting
 525 timestamp_format long-iso
 526
 527 # only make a snapshot if things have changed
 528 snapshot_create onchange
 529 # I could make this different from target_preserve,
 530 # if one disk had less space.
 531 # for now, keeping them equal.
 532 snapshot_preserve $std_preserve
 533 snapshot_preserve_min 2h
 534 snapshot_dir btrbk
 535 # so, total backups = ~58
 536 target_preserve $std_preserve
 537 target_preserve_min 2h
 538
 539 # i tried this when investigating: clone no source subvolume found error
 540 #incremental_prefs sro:1 srn:1 sao san:1 aro:1 arn:1
 541
 542 # if something fails and it's not obvious, try doing
 543 # btrbk -l debug -v dryrun
 544
 545 rate_limit $rate_limit
 546 EOF
 547
 548 if $incremental_strict; then
 549   cat >>/etc/btrbk$conf_suf.conf <<EOF
 550 incremental strict
 551 EOF
 552 fi
 553
 554 qconf() {
 555   case $sub in
 556     q)
 557       # q has sensitive data i dont want to backup for so long
 558       cat >>/etc/btrbk$conf_suf.conf <<EOF
 559 snapshot_preserve $q_preserve
 560 snapshot_preserve_min 2h
 561 snapshot_dir btrbk
 562 target_preserve $q_preserve
 563 target_preserve_min 2h
 564 EOF
 565       ;;
 566   esac
 567
 568 }
 569
 570 # make /q be last
 571 mp_count=${#mountpoints[@]}
 572 for (( i=0; i < mp_count - 1 ; i++ )); do
 573   if [[ ${mountpoints[i]} == /q ]]; then
 574     unset "mountpoints[i]"
 575     mountpoints+=(/q)
 576   fi
 577 done
 578
 579 for m in ${mountpoints[@]}; do
 580   case $m in
 581     /o)
 582       vol=/mnt/o
 583       ;;
 584     *)
 585       vol=/mnt/root
 586       ;;
 587   esac
 588
 589   sub=${m#/}
 590   if [[ $source ]]; then
 591     cat >>/etc/btrbk$conf_suf.conf <<EOF
 592 volume ssh://$bbksource$vol
 593 subvolume $sub
 594 EOF
 595     qconf
 596     cat >>/etc/btrbk$conf_suf.conf <<EOF
 597 target send-receive $vol/btrbk
 598 EOF
 599   fi
 600   if (( ${#targets[@]} )); then
 601     cat >>/etc/btrbk$conf_suf.conf <<EOF
 602 volume $vol
 603 subvolume $sub
 604 EOF
 605     qconf
 606     for tg in ${targets[@]}; do
 607       # handle ipv6
 608       if [[ $tg == *:* ]]; then
 609         tg="[$tg]"
 610       fi
 611       cat >>/etc/btrbk$conf_suf.conf <<EOF
 612 target send-receive ssh://$tg$vol/btrbk
 613 EOF
 614     done
 615   fi
 616 done
 617
 618 # todo: umount first to ensure we don't have any errors
 619 # todo: do some kill fuser stuff to make umount more reliable
 620
 621
 622 if $conf_only; then
 623   mexit 0
 624 fi
 625
 626
 627
 628 if $dry_run; then
 629   m btrbk -c /etc/btrbk$conf_suf.conf -v -n $cmd_arg
 630   mexit 0
 631 fi
 632 # -q and just using the syslog option seemed nice,
 633 # but it doesn't show when a send has a parent and when it doesn't.
 634 m btrbk -c /etc/btrbk$conf_suf.conf $preserve_arg $verbose_arg $progress_arg $cmd_arg
 635
 636 if $early; then
 637   exit 0
 638 fi
 639
 640 # todo: tp not valid anymore.
 641 # if we have it, sync to systems which don't
 642 if mountpoint $rsync_mountpoint >/dev/null; then
 643   for tg in ${targets[@]}; do
 644     case $tg in
 645       tp)
 646         dirs=(/p/c/machine_specific/tp)
 647         for x in /p/c/machine_specific/*.hosts; do
 648           if grep -qxF $tg $x; then
 649             dirs+=(${x%.hosts})
 650           fi
 651         done
 652         m rsync -aSAXPH --specials --devices --delete --relative ${dirs[@]} root@$tg:/
 653         ;;
 654     esac
 655   done
 656 fi
 657
 658 subvols=()
 659 for mp in "${mountpoints[@]}"; do
 660   subvols+=("${mp##*/}")
 661 done
 662 if [[ $source ]]; then
 663   m mount-latest-subvol "${subvols[@]}"
 664 else
 665   for tg in ${targets[@]}; do
 666     m /a/exe/mount-latest-remote "$tg" "${subvols[@]}" || ret=$?
 667   done
 668 fi
 669
 670 if [[ $ret == 0 ]]; then
 671   for tg in ${targets[@]}; do
 672     :
 673     #ssh root@$tg /a/exe/mail-backup-clean
 674   done
 675 fi
 676
 677 mexit $ret
 678
 679 # todo: move variable data we don't care about backing up
 680 # to /nocow and symlink it.
 681
 682
 683 # background on btrbk timezones. with short/long, timestamps use local time.
 684 # for long, if your local time moves backwards, by moving timezones or
 685 # for an hour when daylight savings changes it, you will temporarily get
 686 # a more aggressive retention policy for the overlapping period, and
 687 # vice versa for the opposite timezone move. The alternative is using
 688 # long-iso, which puts timezone info into the timestamp, which means
 689 # that instead of shifting time, you shift the start of day/week/month
 690 # which is used for retention to your new local time, which means for
 691 # example, if you moved forward by 8 hours, the daily/weekly/monthly
 692 # retention will be 8 hours more aggressive since midnight is at a new
 693 # time, unless you fake the timzeone using the TZ env variable.
 694 # However, in the short term, there will be no inconsistencies.
 695 # I don't see any problem with shifting when the day starts for
 696 # retention, so I'm using long-iso.
 697
 698 # note to create a long-iso timestamp: date +%Y%m%dT%H%M%S%z