Cyrille Bollu wrote at 17:53 +0100 on Nov 22, 2007:
 > is there something to do to prevent "tar" to lookup for username when it's 
 > estimating the size of the DLE's (like when you do "ls -ln" instead of "ls 
 > -l")?
 > 
 > It seems that this process puts a very high load on my LDAP server... Such 
 > a high load that I'm planing to install a new LDAP slave only for the 
 > backup
 > 
 > Any clue?

>From gtar docs...

`--numeric-owner'
     This option will notify `tar' that it should use numeric user and
     group IDs when creating a `tar' file, rather than names.

I'm not sure amanda supports passing arbitrary args to gtar.  In
client-src/sendbackup-gnutar.c, the mechanism used to optionally
support --atime-preserve was a compile (configure) time option.  There
used to be a --enable-gnutar-atime-preserve option to configure, but
that looks like it has disappeared (it was never really an advisable
option).

If there is a run-time way to add options to the gtar invocation, I
don't know about it, but I'm sure someone will chime in if there is.


Maybe we should just turn on --numeric-owner by default.  I can't
think of any good reason why we shouldn't.  On extraction for restore,
it won't really help to have the username in the archive.  I don't
think gtar supports translating username to a different uid if the uid
differs on the extracted system.

Hmmm... after testing, it seems that gtar does look up the username on
extraction and change the uid accordingly.  If the username on the
system where you untar has a different uid than on the system where
the archive was created, gtar will extract and chown a file such that
the extracted file has the new uid (unless you extract with
--numeric-owner).

For amanda, however, where you typically restore in order to recreate
a system exactly as it was before, that seems to be an unnecessary
option.  But I suppose I could see a case where the uid for user "joe"
has changed (for whatever reason) and he wants a file of his restored
from a year ago before the uid change.  In that case, he'd probably
want the file to still be owned by joe even though the BOFH changed
his uid on him.

In any case, allowing --numeric-owner to be optionally used seems like
a reasonable thing for amanda to support.

Beyond the scope of the immediate question, but related... what about
ldap name service caching?  I'll admit my lack of knowledge in this
area, but that seems like one possible way to help take some of the
load off the server.