[Samba] restarting samba using a cron job on Debian

[Lars Hanke]

For some reason my secondary DC loses sync every once in a while. It 
looks like this in samba-tool drs showrepl:

Last attempt @ Thu Nov 19 13:53:09 2015 CET failed, result 5 
(WERR_ACCESS_DENIED)
229 consecutive failure(s).
Last success @ Wed Nov 18 18:48:07 2015 CET

Restarting samba fixes the issue for an unpredictable time. Sometimes 
hours, sometimes many weeks. So I wrote a script to restart samba in 
this case:

#!/bin/bash
#
# Check if samba replication broke down and restart samba in this case
#
SAMBA_TOOL=/usr/bin/samba-tool
SED=/bin/sed
MAIL=/usr/bin/mail
RM=/bin/rm
MKTMP=/bin/mktemp

FAIL=`$SAMBA_TOOL drs showrepl | $SED -n "/^\s*[1-9][0-9]* consecutive 
failure(s)\.$/p"`

if [[ -n "$FAIL" ]]; then
   TMP=$($MKTMP)
   $SAMBA_TOOL drs showrepl > "$TMP"
   echo "Restart ..." >> "$TMP"
   /etc/init.d/samba restart >> "$TMP"
   echo "... done!" >> "$TMP"
   $MAIL -s 'DC2 restart' sysop at example.com < "$TMP"
   $RM -f "$TMP"
fi

And it works perfectly, if I run it manually. However, the idea is to 
run it by cron every 5 minutes. But when it's run from cron restarting 
samba fails:

Restart ...
Stopping NetBIOS name server: nmbd.
Stopping SMB/CIFS daemon: smbd.
Stopping Samba AD DC daemon: samba.
Starting Samba AD DC daemon: samba failed!
... done!

Running the same script manually from a root shell works however fine.

The system is Debian Jessie using samba 4.1.17-Debian. I start the 
script using the following entry in root's crontab:

*/5 * * * * /root/samba-restart.sh

Any ideas what I'm doing wrong?

Thanks for your help,
  - lars.