own mailserver, lots of improvements

[distro-setup] / check-subvol-stale

diff --git a/check-subvol-stale b/check-subvol-stale
old mode 100755 (executable)
new mode 100644 (file)
index f278188..1277182
--- a/check-subvol-stale
+++ b/check-subvol-stale
@@ -14,7 +14,15 @@
 # limitations under the License.
 
 # usage: $0 SUBVOL_MOUNTPOINT...
-# if latest subvols $@ are not mounted, exit 1, print message, and touch /nocow/btrfs-stale/$subvol
+#
+# In git, this is not not executable because it's meant to be installed
+# using ./install-my-scripts
+#
+# If latest subvols $@ are not mounted, exit 1, print message, and touch
+# /nocow/btrfs-stale/$subvol
+#
+# Either SUBVOL_MOUNTPOINT is a snapshot of the latest, or
+# the latest snapshot is snapshot of SUBVOL_MOUNTPOINT.
 
 [[ $EUID == 0 ]] || exec sudo -E "$BASH_SOURCE" "$@"
 
@@ -31,7 +39,7 @@ ret=0
 for d; do
     vol=${d##*/}
     cd /mnt/root/btrbk
-    snaps=($vol.20*)
+    snaps=($vol.20*) # Assumes we are in the 21st century.
     if [[ ! $snaps ]]; then
         # no snapshots yet
         continue
@@ -45,12 +53,17 @@ for d; do
         done | sort -r | head -n 1 | awk '{print $2}'
              )
     if [[ ! $last_snap ]]; then
-        echo "$d stale"
+        # should not happen.
+        echo "$0: error: could not find latest snapshot for $d among ${snaps[@]}"
         ret=1
         continue
     fi
     stale=true
-    if btrfs sub show $d 2>/dev/null | sed '0,/^\t*Snapshot(s):/d;s/^\s*//' | \
+    # check that $d has $last_snap as a snapshot,
+    # or else $d is a snapshot of $last_snap. In the second
+    # case, we use a uuid comparison, which if I remember from the
+    # docs, is a bit more robust, perhaps to renames.
+    if btrfs sub show $d 2>/dev/null | sed '0,/^\s*Snapshot(s):/d;s/^\s*//' | \
             grep -xF btrbk/$last_snap &>/dev/null; then
         stale=false
     else
@@ -72,4 +85,3 @@ for d; do
     fi
 done
 exit $ret
-