Due to the way Ubuntu works (using Upstart instead of inittab), if you're using Webmin/Usermin with Ubuntu, simply delete the following file to make the “Bootup and Shutdown” page and the “Start at boot time” feature working:

/etc/inittab

If you are getting the “The module could not find the mount point for your home directories filesystem /home. Quotas editing has been disabled.” error, add this line to your /etc/fstab file:

/dev/simfs / reiserfs rw,usrquota,grpquota 0 0

If you are getting an error about missing Socket6 module when enabling IPv6, run this command at the root prompt:

apt-get install libsocket6-perl