Mounting system directories from network

Question

I was thinking about how to keep write access to my Raspberry Pi's root file system (residing on a SD card) at a minimum. Of course, /var is a primary candidate for being kept somewhere else.

I have a NAS storage in my home network. In order to get proper handling of file ownership, permissions etc. I was thinking about mounting an image file (located on the NAS), via the loopback device, to /var.

1) Can I do this by just adding the appropriate lines to /etc/fstab and be done with it, or is /var needed too early in the boot process for this to work out? What should I be aware of?

2) Am I thinking too complicated and is there a much easier way to achieve this? (NFS mounting is another option, but I haven't activated this one on the NAS yet as, to be honest, the NFS admin interface on the NAS sucks - and I have no idea if this would actually change anything.)

Any thoughts would be appreciated: Can I mount system directories like /var from the network, and what would I have to take care of?

Answer 1

You may want to have a look at this:

https://wiki.archlinux.org/index.php/Using_tmpfs_for_/var/*

Some extract:

Using tmpfs for high read/write activitiy folders like /var/{log,tmp,etc,etc} can be considered useful for both increasing performance or life span of storage devices. This can be done with altering /etc/fstab, in this case you will lose those files on next reboot, but a number of the /var/ directory content want to be kept for most usages like /var/log , /var/tmp eg.

This can be achieved with daemon scripts.

Answer 2

There is a blog entry on how to put the entire root filesystem on NFS, and boot the Raspberry from there:

http://var-blog-messages.blogspot.co.uk/2012/05/set-up-your-raspberry-pi-like-pro.html

The generic documentation on how to boot your root file system via NFS is here:

http://www.tldp.org/HOWTO/NFS-Root.html

Will give it a try and write a quick summary if successful.

Edit: Nothing much to summarize. Works like a charm.