varball - keep /var across reboots on FreeBSD

The idea behind varball is to enable the use of tmpfs(4) or md(4)/mdmfs(8) for /var without giving up persistence therein.

It uses an rc(8) boot/shutdown script and tar(1) to archive /var into a tar file on shutdown and to extract it again on boot.

Install varball

After cloning this repository, you can either

• copy the etc/rc.d/varball script to /etc/rc.d/ or /usr/local/etc/rc.d, or
• configure rc(8) to use your clone by adding local_startup="$local_startup /path/to/varball/etc/rc.d" to /etc/rc.conf

Enable varball

To enable varball, add varball_enable="YES" to /etc/rc.conf. Set varball_file and varball_dir if you want to use values other than the defaults (/var.tar and /var, respectively).

Switch /var to tmpfs(4)

After installing and enabling varball, it's time to start using it. The easiest way to do this is from single-user mode. Use shutdown now to ensure that varball is "stopped" for the first time, creating the initial tar file. After starting the single-user shell, umount (or remove) /var. Change (or add) the /var mountpoint in /etc/fstab:

tmpfs	/var	tmpfs	rw	0	0

Exit single-user mode (or reboot).

Caveats

The tar file is refreshed by rc.shutdown(8), which is in turn called by shutdown(8). Using reboot(8), halt(8), or any other method that bypasses rc.shutdown(8) will prevent the tar file from being updated. This includes crashes/panics.