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Re: RFC: New required package: libblkid1


On Thu, Mar 20, 2003 at 01:27:19AM -0500, Theodore Ts'o wrote:

> On Thu, Mar 20, 2003 at 02:38:38PM +0900, Miles Bader wrote:
> > Really only /etc needs to be available on the root filesystem; /run
> > (or /var/my-persistant-cache, or whatever it's called) doesn't -- it
> > can be mounted very early if necessary for special situations.
> /etc/blkid.tab may be necessary to find the /var partition.  (i.e., if
> /etc/fstab has LABEL=var, and you don't want to search all of the 2000
> block devices in the system, then you want to use /etc/blkid.tab to be
> able to quickly find the var partition.)
> Similarly, /etc/ld.so.cache is necessary to run the mount command (and
> any other dynamically linked executable).  So saying that they can
> live on another partition is simply not correct, and seems to indicate
> that the person making the argument doesn't understand the issues
> involved.  
> If "/run can be mounted very early", then there's no point to have a
> separate /run directory to clutter up the root partition.  /var can
> simply be mounted early.  The whole point of /run is because it needs
> to be on the root.  The question then is that if /run must be on the
> root, and /etc must be on the root, why bother separating the two?
> The reason why it's in /etc/blkid.tab and not /var/run/blkid.tab is
> *precisely* because it must be on the root partition.  /var might not
> be on the root partition.

The thing with these caches is that if you live on a fairly static
system, they may still be on fs that's always R/O except for maintenance
tasks such as installing software or changing disks.

I think /etc is not a problem for /etc/ld.so.cache or /etc/blkid.tab,
but it /is/ a problem for information that changes during the boot
process (for which /run would be a better candidate) or at run time
(/var/run if not persistent, /var/lib if it is).

So as long as you don't also use /etc/blkid.tab to keep state such as
mount counters or timestamps, but separate that so it can be put in
/var/run or /var/lib and the tools can work with a missing statefile
before /var is mounted, it seems fine to use /etc.



E-Advies - Emile van Bergen           emile@e-advies.nl      
tel. +31 (0)70 3906153           http://www.e-advies.nl    

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