Regular → Executable
+186
-15
@@ -1,22 +1,193 @@
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#!/bin/sh
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set -e
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# Planner for periodic backups.
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#
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# busybox crond is deliberately not used here: when the container runs under a
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# non-root uid (a very common k8s securityContext) crond loads no crontab at
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# all and never says why - it just keeps printing "wakeup dt=60" forever while
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# no backup is ever made. This loop does the same job, works under any uid and
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# fails loudly on a bad schedule.
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# crond runs jobs with a bare environment (HOME/PATH/SHELL only), so the
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# container env is dumped here and sourced back by backup.sh on every run.
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ENV_FILE=/tmp/container.env
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export -p | grep -v -E "^export (PWD|SHLVL|OLDPWD|_)=" > "$ENV_FILE"
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chmod 600 "$ENV_FILE"
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# -f matters: the schedule is full of '*' and word splitting would otherwise
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# expand them against the files in the working directory.
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set -euf
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# Create crontab in a writable location and set proper permissions
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mkdir -p /tmp/crontabs
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echo "${CRONTAB:-"0 * * * *"} /scripts/backup.sh --from-cron >> /proc/1/fd/1 2>&1" > /tmp/crontabs/root
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chmod 644 /tmp/crontabs/root
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SCHEDULE_RAW="${CRONTAB:-0 * * * *}"
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POLL_INTERVAL="${POLL_INTERVAL:-20}"
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echo "[entrypoint] schedule: ${CRONTAB:-"0 * * * *"} (TZ=${TZ:-UTC})"
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log() { echo "[scheduler] $*"; }
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die() { echo "[scheduler] FATAL: $*" >&2; exit 1; }
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# Run initial backup (do not abort the container if it fails)
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/scripts/backup.sh || echo "[entrypoint] initial backup failed, continuing to crond"
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# A value coming from .env, a configmap or a helm chart may carry quotes or a
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# trailing CR; both silently break the schedule, so strip them up front.
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SCHEDULE=$(printf '%s' "$SCHEDULE_RAW" | tr -d '\r' \
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| sed -e 's/^"\(.*\)"$/\1/' -e "s/^'\(.*\)'\$/\1/")
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# Start crond in foreground with debug output
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exec crond -f -c /tmp/crontabs -d 0
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MONTH_NAMES="jan feb mar apr may jun jul aug sep oct nov dec"
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DOW_NAMES="sun mon tue wed thu fri sat"
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# Resolve a three-letter month/weekday name to its number, echo the input back
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# when it is not a name.
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resolve_name() { # $1=token $2=names $3=base
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_tok=$(echo "$1" | tr '[:upper:]' '[:lower:]')
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_n=0
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for _w in $2; do
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if [ "$_tok" = "$_w" ]; then
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echo $((_n + $3))
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return 0
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fi
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_n=$((_n + 1))
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done
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echo "$1"
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}
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# Drop a leading zero so that "07" is not read as an invalid octal number.
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strip_zero() {
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_v=${1#0}
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[ -n "$_v" ] || _v=0
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echo "$_v"
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}
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# Expand one crontab field into the explicit list of values it matches.
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# Supports *, N, a-b, a,b, */n, a-b/n and N/n.
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expand_field() { # $1=spec $2=lo $3=hi $4=field name $5=names $6=names base
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_spec=$1; _lo=$2; _hi=$3; _name=$4; _names=$5; _base=$6
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_out=''
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_oifs=$IFS
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IFS=,
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for _part in $_spec; do
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IFS=$_oifs
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_step=1
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case $_part in
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*/*)
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_step=${_part##*/}
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_part=${_part%%/*}
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;;
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esac
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case $_step in
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''|*[!0-9]*) die "$_name: bad step in '$_spec'" ;;
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esac
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_step=$(strip_zero "$_step")
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[ "$_step" -ge 1 ] || die "$_name: step must be >= 1 in '$_spec'"
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case $_part in
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'*')
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_s=$_lo; _e=$_hi
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;;
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*-*)
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_s=$(resolve_name "${_part%%-*}" "$_names" "$_base")
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_e=$(resolve_name "${_part##*-}" "$_names" "$_base")
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;;
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*)
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_s=$(resolve_name "$_part" "$_names" "$_base")
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# "N/step" means "from N to the end of the range", like vixie cron.
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if [ "$_step" -gt 1 ]; then _e=$_hi; else _e=$_s; fi
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;;
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esac
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for _v in "$_s" "$_e"; do
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case $_v in
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''|*[!0-9]*) die "$_name: '$_part' is not a number or a known name" ;;
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esac
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done
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_s=$(strip_zero "$_s")
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_e=$(strip_zero "$_e")
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[ "$_s" -ge "$_lo" ] && [ "$_e" -le "$_hi" ] \
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|| die "$_name: '$_part' is outside ${_lo}-${_hi}"
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[ "$_s" -le "$_e" ] || die "$_name: reversed range '$_part'"
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_i=$_s
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while [ "$_i" -le "$_e" ]; do
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_out="$_out $_i"
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_i=$((_i + _step))
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done
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IFS=,
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done
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IFS=$_oifs
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[ -n "$_out" ] || die "$_name: empty field"
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echo "$_out"
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}
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in_list() { # $1=list $2=value
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case " $1 " in
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*" $2 "*) return 0 ;;
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esac
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return 1
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}
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# Word splitting is the point here, and globbing is off (set -f).
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# shellcheck disable=SC2086
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set -- $SCHEDULE
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[ $# -eq 5 ] || die "CRONTAB must have 5 fields, got $#: '$SCHEDULE_RAW'"
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SPEC_MIN=$1 SPEC_HOUR=$2 SPEC_DOM=$3 SPEC_MON=$4 SPEC_DOW=$5
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LIST_MIN=$(expand_field "$SPEC_MIN" 0 59 minute '' 0)
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LIST_HOUR=$(expand_field "$SPEC_HOUR" 0 23 hour '' 0)
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LIST_DOM=$(expand_field "$SPEC_DOM" 1 31 day '' 0)
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LIST_MON=$(expand_field "$SPEC_MON" 1 12 month "$MONTH_NAMES" 1)
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LIST_DOW=$(expand_field "$SPEC_DOW" 0 7 weekday "$DOW_NAMES" 0)
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# Sunday is both 0 and 7.
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if in_list "$LIST_DOW" 7 && ! in_list "$LIST_DOW" 0; then
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LIST_DOW="$LIST_DOW 0"
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fi
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# crontab(5): when both day-of-month and day-of-week are restricted, a run
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# happens if either of them matches, not both.
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if [ "$SPEC_DOM" != '*' ] && [ "$SPEC_DOW" != '*' ]; then
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DAY_MATCH=or
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else
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DAY_MATCH=and
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fi
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log "schedule: $SCHEDULE (TZ=${TZ:-UTC}, now $(date '+%F %T %z'))"
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log "expanded: min=[${LIST_MIN# }] hour=[${LIST_HOUR# }] dom=[${LIST_DOM# }] mon=[${LIST_MON# }] dow=[${LIST_DOW# }] day-match=$DAY_MATCH"
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matches_now() { # $1=minute $2=hour $3=dom $4=month $5=dow
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in_list "$LIST_MIN" "$1" || return 1
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in_list "$LIST_HOUR" "$2" || return 1
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in_list "$LIST_MON" "$4" || return 1
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if [ "$DAY_MATCH" = or ]; then
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in_list "$LIST_DOM" "$3" || in_list "$LIST_DOW" "$5" || return 1
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else
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in_list "$LIST_DOM" "$3" || return 1
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in_list "$LIST_DOW" "$5" || return 1
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fi
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return 0
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}
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TERMINATE=0
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trap 'TERMINATE=1' TERM INT
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# Initial backup: do not abort the container if it fails, the schedule matters
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# more than this one run.
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/scripts/backup.sh || log "initial backup failed, continuing to the schedule"
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# The startup backup counts as this minute's run, otherwise a schedule that
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# matches the minute the container came up would immediately back up twice.
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LAST_RUN=$(date '+%Y-%m-%dT%H:%M')
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while [ "$TERMINATE" -eq 0 ]; do
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# Polling instead of sleeping to the minute boundary: a backup can take
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# minutes and the clock can jump, LAST_RUN is what keeps a minute from
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# firing twice.
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# shellcheck disable=SC2046
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set -- $(date '+%Y-%m-%dT%H:%M %M %H %d %m %w')
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KEY=$1
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MIN=$(strip_zero "$2"); HOUR=$(strip_zero "$3")
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DOM=$(strip_zero "$4"); MON=$(strip_zero "$5"); DOW=$(strip_zero "$6")
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if [ "$KEY" != "$LAST_RUN" ] && matches_now "$MIN" "$HOUR" "$DOM" "$MON" "$DOW"; then
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LAST_RUN=$KEY
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log "triggered at $KEY"
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/scripts/backup.sh || log "backup failed, waiting for the next run"
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fi
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# Backgrounded so that SIGTERM is handled right away instead of after the
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# whole interval.
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sleep "$POLL_INTERVAL" &
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wait $! || true
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done
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log "terminating"
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Reference in New Issue
Block a user