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Re: Upgrade a mail server

On Tue, Feb 19, 2002 at 05:51:20PM +1100, Russell Coker wrote:
> When I configured it to use hashed indexes to /etc/passwd (this was on
> AIX which does it much better than Linux) the load average dropped to
> between 0.5 and 4 (depending on the time of day), CPU usage was often
> less than 100%, and everything was responsive!

i was thinking of  hashed passwd/shadow files when i said it would scale
up to at least 10000 users.

> > you don't need nscd, just hashed map files for
> > /etc/{passwd,group,shadow).  there's a Makefile in /var/lib/misc
> > which handles that.
> The problem is that the utility programs like passwd(1) aren't smart
> enough to update the hash, and the libraries that read from the hashes
> aren't smart enough to check the time stamps and use /etc/passwd if
> it's more recent.  AIX does this much better.

i found (when i was using hashed passwd files) that the following in
root's crontab is adequate:

0/5 * * * cd /var/lib/misc ; make

or run it every minute if you prefer.

> > i'd love to convert it over to Maildir/ but haven't yet found any way
> > that doesn't involve many hours of downtime while converting the
> > mailboxes from mbox format to Maildir.
> >
> > one of these days i'll have the time to sit down and work out a good
> > solution to the problem.  i've got some ideas but no time to work them
> > out.
> Conversion doesn't require system down-time.  

see comments in previous messages.  whether it's real downtime or just
apparent downtime to the user doesn't really matter - the users are
going to complain anyway.

> Firstly you create Maildir directories.  Then you can convert the mail
> server to Maildir delivery in a matter of minutes, then you run a
> conversion script to convert mbox files to Maildir (may take hours or
> even a day depending on system speed and size of the spool).  When you
> think it's about half done you change the POP and IMAP servers to read
> from Maildir instead of mbox.  The end result is that there is a
> matter of minutes of actual down time, 

no, that is "hours or even a day" of down time.


craig sanders <cas@taz.net.au>

Fabricati Diem, PVNC.
 -- motto of the Ankh-Morpork City Watch

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