add DELETE_OUTDATED to prune old remote bkfiles

README.md

@@ -204,12 +204,38 @@ If you want to cleanup the backup file locally after uploading it upstream, set
 `CLEAR_BKFILE` environment variable to a non-empty value. `zfsbk.sh` will maintain the local
 backup regardless of this variable if the upload failed.
 
+    # delete generated bkfile locally after successful upload
+    UPLOAD_PATH="..." CLEAR_BKFILE=yep /usr/local/sbin/zfsbk.sh mybk 7
+
+Ask `zfsbk` to remove an old sequence remotely before uploading a new one:
+
+    # remove all bkfiles of old sequence *remotely* before uploading new one
+    UPLOAD_PATH="..." DELETE_OUTDATED="yep" /usr/local/sbin/zfsbk.sh mybk 7
+
+This allows you to cap the size taken by backups at the remote.
 
 # Managing multiple ZFS Pools
 
 Simply run these scripts once for each pool, setting the _ZPOOL_ environment variable
 accordingly.
 
+# Summary of control variables
+
+Here's all environment variables controlling the behavior or `zfssnap` and `zfsbk`:
+
+## zfssnap
+
+* `ZPOOL` [str] name of the ZFS pool to operate on.
+* `EXCLUDES` [str] space-separated list of dataset names to exclude from snapshots. Overrides defaults.
+* `EXTRA_EXCLUDES` [str] space-separated list of dataset names to exclude from snapshots in addition to defaults.
+
+## zfsbk
+
+* `UPLOAD_PATH` [str] Upload generated bkfile to this remote location; 'scp://' or 'rsync://'
+* `CLEAR_BKFILE` [any] If non-empty, remove copy of generated bkfile after successful remote upload.
+* `DELETE_OUTDATED` [any] If non-empty, remove old backup sequence remotely before uploading first bkfile of a new sequence.
+
+
 # Ancillaries
 
 ## Warranty

zfsbk.sh

@@ -102,20 +102,29 @@ fi
 # upload backup to remote location
 if [ "x$UPLOAD_PATH" != x ]
 then
+    upload_excode=1 # assume failure, override with actual outcome
     #echo "Archiving $bkfile remotely..."
     if echo "$UPLOAD_PATH" | grep -qE '^rsync://'
     then
         rsync -qz $bkfile ${UPLOAD_PATH#rsync://}
+        upload_excode=$?
     elif echo "$UPLOAD_PATH" | grep -qE '^scp://'
     then
-        scp -BCq $bkfile ${UPLOAD_PATH#scp://}
+        SCP_PATH=${UPLOAD_PATH#scp://}
+        if [ "$num_snaps" -eq 1 -a "x$DELETE_OUTDATED" != x ]
+        then
+            echo "Clearing old zbk-${bkname}* sequence remotely..."
+            echo "rm zbk-${bkname}*" | sftp -q -b- $SCP_PATH
+        fi
+        scp -BCq $bkfile "$SCP_PATH"
+        upload_excode=$?
     else
         echo "UPLOAD_PATH not understood! '$UPLOAD_PATH'"
         echo "Expecting rsync://.. or scp://.."
         exit 1
     fi
     # remove local backup if requested & upload was successful
-    if [ $? -eq 0 -a "x$CLEAR_BKFILE" != x ]
+    if [ $upload_excode -eq 0 -a "x$CLEAR_BKFILE" != x ]
     then
         # remove backup file if requested
         rm -f $bkfile