add support for cleaning zfs system snapshots

sau/freebsd.py

@@ -10,11 +10,14 @@ import sau.helpers
 PKG_PATH='/usr/sbin/pkg'
 SERVICE_PATH='/usr/sbin/service'
 FREEBSD_UPDATE_PATH='/usr/sbin/freebsd-update'
+ZFS='/sbin/zfs'
 
 # regex to identify rc.d-files
 rc_script_re = re.compile(r'^(?:/usr/local)?/etc/rc\.d/(.*)$')
 # regex to parse packages
 pkg_upgrade_re = re.compile(r'^\s([^\s]*): ([^\s]*) -> ([^\s]*).*$') 
+# regex for system zfs snapshots
+system_snaps_re=re.compile(r'^zroot/ROOT/default@\d{4}-\d\d-\d\d-\d\d:\d\d:\d\d-\d+(?:\s|$)')
 
 
 def identify_service_from_bin(exe):
@@ -55,7 +58,24 @@ def restart_service(service):
     else:
         log.info("restarted service {}".format(service))
 
+def clean_zfs(to_keep=5):
+    log = logging.getLogger(sau.LOGNAME)
+    cmd = [ ZFS, 'list', '-t', 'snapshot', '-H' ]
+    ret, out, err = sau.helpers.exec_cmd(cmd, timeout=300)
+
+    snapshots = sorted([l.split()[0] for l in out.splitlines() if re.match(system_snaps_re, l)], reverse=True)
+
+    if to_keep < 1:
+        log.warning(f'set to save {to_keep} snapshots; NO WAY!, will keep one anyway')
+        to_keep = 1
+
+    for s in snapshots[to_keep:]:
+        log.info(f'Removing old system snapshot "{s}"')
+        cmd = [ ZFS, 'destroy', '-R', s ]
+        ret, out, err = sau.helpers.exec_cmd(cmd, timeout=600)
+
 def system_upgrade():
+    conf = sau.config
     log = logging.getLogger(sau.LOGNAME)
     # this is how freebsd wants it...
     time.sleep(random.randint(0, 3600))
@@ -70,6 +90,8 @@ def system_upgrade():
             log.info('System updates installed:')
             for line in out.splitlines():
                 log.info(line)
+            keep_snapshots = conf.getint('default', 'keep_snapshots', fallback=4)
+            clean_zfs(keep_snapshots)
             return True
     else:
         log.warning('System upgrade failed (return code {}):'.format(ret))