use flock automatic lock for upgrade

fix nextcloud#1756

Signed-off-by: Adam Monsen <haircut@gmail.com>

docker-entrypoint.sh

@@ -124,15 +124,15 @@ if expr "$1" : "apache" 1>/dev/null || [ "$1" = "php-fpm" ] || [ "${NEXTCLOUD_UP
             rsync_options="-rlD"
         fi
 
+        # Prevent multiple images syncing simultaneously:
         # If another process is syncing the html folder, wait for
-        # it to be done, then escape initalization.
-        # You need to define the NEXTCLOUD_INIT_LOCK environment variable
-        lock=/var/www/html/nextcloud-init-sync.lock
+        # it to be done, then escape initalization
         count=0
         limit=10
 
-        if [ -f "$lock" ] && [ -n "${NEXTCLOUD_INIT_LOCK+x}" ]; then
-            until [ ! -f "$lock" ] || [ "$count" -gt "$limit" ]
+        (
+        if ! flock -n 9; then
+            until flock -n 9 || [ "$count" -gt "$limit" ]
             do
                 count=$((count+1))
                 wait=$((count*10))
@@ -145,8 +145,6 @@ if expr "$1" : "apache" 1>/dev/null || [ "$1" = "php-fpm" ] || [ "${NEXTCLOUD_UP
             fi
             echo "The other process is done, assuming complete initialization"
         else
-            # Prevent multiple images syncing simultaneously
-            touch $lock
             rsync $rsync_options --delete --exclude-from=/upgrade.exclude /usr/src/nextcloud/ /var/www/html/
 
             for dir in config data custom_apps themes; do
@@ -234,10 +232,9 @@ if expr "$1" : "apache" 1>/dev/null || [ "$1" = "php-fpm" ] || [ "${NEXTCLOUD_UP
 
             fi
 
-            # Initialization done, reset lock
-            rm $lock
             echo "Initializing finished"
         fi
+        ) 9> /var/lock/nextcloud-init-sync.lock
     fi
 
     # Update htaccess after init if requested