From SambaWiki

Topics I want to write about.. but might not get to.

By Bryan Popham
9/9/13 - Ver. 0.1

Backup, Migration and/or Recovery

Migrate from a old ver of Samba4 in Ubuntu (Samba4Alpha11 to Samba4 Current)

stop all DC and tar up the one your upgrading. scp it to the new server and unpack it..
git the latest samba, configure --enable-debug --enable-selftest
sudo make install
make a new samba dir with the new bin, sbin, modules & lib from make install
the all the rest of the folders from the old build
make sure the hosts, resolv.conf, fqdn & IP are the the same as the old server
run "samba-tool dbcheck --fix" 3x times till no errors
run "samba-tool dbcheck --reset-well-known-acls --fix" 2x times till no errors
run ~/samba-master/source4/scripting/bin/samba_upgradedns
rerun make install

Recovering from a TAR backup in Ubuntu

Proper way to backup Samba4 AD DC with rsnapshot

Simple Fix

Setting the hardware clock.
Sometimes when the power has been out for over 30 mins and the server
boots with no internet/intranet access to reach NTP the server will revert
to its hardware clock knocking the AD DC offline

From my howto -

Set system clock and date
user@svr:~$sudo date 100910032012.02

Set hardware clock and date
user@svr:~$sudo hwclock --set --date="10/09/12 10:13:00"