Prevent multiple restic backups from running at once

Dockerfile

@@ -16,7 +16,7 @@ ENV RESTIC_TAG=latest
 RUN apk add --update --no-cache ca-certificates fuse openssh-client bash tzdata
 WORKDIR /root
 COPY --from=build /usr/local/src/restic/restic /usr/local/bin
-COPY entrypoint.sh backup.sh prune.sh forget.sh ./
+COPY entrypoint.sh backup.sh do_backup.sh prune.sh forget.sh ./
 ENV PATH="./:${PATH}"
 RUN chmod a+x ./*.sh
 RUN mkdir -p /var/spool/cron/crontabs \

backup.sh

@@ -8,51 +8,9 @@ log() {
     echo "[$(date +"%Y-%m-%d %H:%M:%S")]$1" | tee -a "$logFile"
 }
 
-showTime() {
-    num=$1
-    min=0
-    hour=0
-    day=0
-    if((num>59));then
-        ((sec=num%60))
-        ((num=num/60))
-        if((num>59));then
-            ((min=num%60))
-            ((num=num/60))
-            if((num>23));then
-                ((hour=num%24))
-                ((day=num/24))
-            else
-                ((hour=num))
-            fi
-        else
-            ((min=num))
-        fi
-    else
-        ((sec=num))
-    fi
-    time="${day}d ${hour}h ${min}m ${sec}s"
-    log "[INFO] Total backup time: ${time}"
-}
-
-start=$(date +%s)
-log "[INFO] Starting backup"
-log "[INFO] Log filename: ${logFile}"
-
-if [ -n "${RESTIC_BACKUP_ARGS}" ]; then
-    log "[INFO] RESTIC_BACKUP_ARGS: ${RESTIC_BACKUP_ARGS}"
-fi
-
-restic backup /data ${RESTIC_BACKUP_ARGS} --tag="${RESTIC_TAG}" | tee -a "$logFile"
+flock -xn /root/restic.lock /root/do_backup.sh
 rc=$?
-if [[ $rc == 0 ]]; then
-    log "[INFO] Backup succeeded"
-else
-    log "[ERROR] Backup failed with status ${rc}"
-    restic unlock
-    copyErrorLog
-    kill 1
+if [[ $rc != 0 ]]; then
+	log "[INFO] Backup already running. Exiting"
 fi
-end=$(date +%s)
-log "[INFO] Finished backup at $(date)"
-showTime $((end-start))
+

do_backup.sh

@@ -0,0 +1,58 @@
+#!/bin/bash
+set -e
+# credit: some of the code for this script inspired by https://github.com/lobaro/restic-backup-docker
+
+logFile="/var/log/restic/backup/$(date +"%Y-%m-%d-%H-%M-%S").log"
+
+log() {
+    echo "[$(date +"%Y-%m-%d %H:%M:%S")]$1" | tee -a "$logFile"
+}
+
+showTime() {
+    num=$1
+    min=0
+    hour=0
+    day=0
+    if((num>59));then
+        ((sec=num%60))
+        ((num=num/60))
+        if((num>59));then
+            ((min=num%60))
+            ((num=num/60))
+            if((num>23));then
+                ((hour=num%24))
+                ((day=num/24))
+            else
+                ((hour=num))
+            fi
+        else
+            ((min=num))
+        fi
+    else
+        ((sec=num))
+    fi
+    time="${day}d ${hour}h ${min}m ${sec}s"
+    log "[INFO] Total backup time: ${time}"
+}
+
+start=$(date +%s)
+log "[INFO] Starting backup"
+log "[INFO] Log filename: ${logFile}"
+
+if [ -n "${RESTIC_BACKUP_ARGS}" ]; then
+    log "[INFO] RESTIC_BACKUP_ARGS: ${RESTIC_BACKUP_ARGS}"
+fi
+
+restic backup /data ${RESTIC_BACKUP_ARGS} --tag="${RESTIC_TAG}" | tee -a "$logFile"
+rc=$?
+if [[ $rc == 0 ]]; then
+    log "[INFO] Backup succeeded"
+else
+    log "[ERROR] Backup failed with status ${rc}"
+    restic unlock
+    copyErrorLog
+    kill 1
+fi
+end=$(date +%s)
+log "[INFO] Finished backup at $(date)"
+showTime $((end-start))