looking for error codes

[Warner Losh]

On Apr 2, 2011, at 1:50 AM, perryh at pluto.rain.com wrote:
> 
>> With respect to my knowledge , no one of the operating systems
>> has a facility to separate read-only and modifiable parts ...
> 
> SunOS 4 had a partial solution to this, by rearranging the FS layout
> so that /usr could be mounted read-only (and often, from a server --
> IIRC a single /usr could be shared among multiple diskless clients).
> They used quite a few symlinks so that things could be found in
> their accustomed places although actually located elsewhere.  The
> scheme was fairly well described in the SunOS 4 manual set; granted
> _finding_ a SunOS 4 manual set these days may be a challenge :)

FreeBSD can do this too.  In fact, NanoBSD relies heavily on having most of the system mounted read-only, and has MFS partitions for /etc and /var.

Warner