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Re: RFC: New required package: libblkid1

On Thu, Mar 20, 2003 at 04:48:14PM +1000, Anthony Towns wrote:
> Is scanning all the partitions for their UUIDs once when the system boots
> such a problem? Or is the aim for people to be able to set the UUID once
> (with tune2fs or mk2fs referring to the device by name), then only have
> to use UUID later, and never have to scan at all?
> If you're ever planning on scanning, doing so once at bootup would seem
> entirely feasible.

If you have a very large number of devices, doing the scan even once
could get very painful.  Consider the case of 4000 block devices, and
needing to find the external journal device for the root filesystem
when the root filesystem is being fsck'ed.  You really want to able to
refer to /etc/blkid.tab from the previous boot session to avoid doing
the scan.  It's just a much more robust scheme.  

And no, /etc/blkid.tab isn't necessary going to be static.  For a
system with a very large number of disks, the possibility that SCSI
id's might get renumbered is a very real one --- suppose a disk dies,
or is removed from the chain?  At that point you will want to do a
rescan, and then save the results to the cache.

> No, the whole point of /run is for it _not_ to have to be on the root
> partition, but, unlike /var, for it to definitely be local.

/var is definitely local.  To quote from the FHS:

       Some portions of /var are not shareable between different systems.  For
       instance, /var/log, /var/lock, and /var/run. 

> Also unlike /var, but like /var/run, files in /run would not be
> persistent.

And for writable files that need to be persistent and available before
other partitions are mounted?

						- Ted

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