Shared /usr in jails

Konrad Heuer kheuer2 at
Mon Sep 22 06:43:34 UTC 2008

On Mon, 22 Sep 2008, Matt Fioravante wrote:

> I want to implement a number of jails for different services on a single
> box.
> Since /usr is the same everywhere I'd like to just mount one copy of it
> read-only to all the jails and then have them each have their own /usr/local
> Someone recommended keeping the main system's /usr separate. This would mean
> building a /usr for the main system and then making a copy of it
> to be shared by the jails.
> Aesthetics and philosophy aside, are there any real security holes in just
> using the systems /usr everywhere if it is mounted read only in the jails?
> THis seems to be the
> approach used by solaris zones.

For a couple of years, I shared /usr on a dozen of hosts by NFS. Worked 
fine, but I mounted it read-only on all but one box. Thus, I had to 
symlink very few files or directories out from /usr to /var.

For security and reliability, I'd recommend to limit read-write access to 

Best regards

Konrad Heuer
GWDG, Am Fassberg, 37077 Goettingen, Germany, kheuer2 at

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