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MFS: Using a RAM Filesystem

Introduction

MFS allows you to place a partition in RAM. The advantage is speed. The disadvantage is that you lose all modifications made to it after each reboot. With a simple rsync setup, this can be resolved, which I'll show you how to do.

Configuration

Partition /tmp

The tmp directory is interesting to move into RAM since the data there is temporary anyway and doesn't need to be stored on the filesystem. Edit the fstab file:

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swap /tmp mfs rw,nodev,nosuid,-s=32768 0 0

Nothing more needs to be done :-)

Partition /var

After installing the necessary packages (such as net-snmp, pftop, pfstat, screen...), configuring the crontab, and configuring chrooted services like bind or an Apache reverse proxy, we can begin setting up the /var partition in MFS by copying its content to the partition reserved for this purpose.

Note that from now on, all modifications to /var should be made from /mfs/var:

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find /var | cpio -dumpv /mfs/

Now let's edit the fstab:

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swap /var mfs rw,-P=/mfs/var,nodev,nosuid,-s=64000 0 0

Syncronisation of modifications

We'll use rsync to update the data. Since we don't need to have everything in real time, a weekly update can be sufficient. Install rsync:

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pkg_add -iv rsync

Add this line to the root crontab:

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3  0  *  *  */1  /usr/local/bin/rsync -az --delete /var/ /mfs/var/

And finally for machine shutdown:

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/usr/local/bin/rsync -vaz --delete /var/ /mfs/var/

References