On Wed, 8 Nov 2006, Mark Crispin wrote:
On Wed, 8 Nov 2006, Dan Mahoney, System Admin wrote:
What about the case where the mail spool is in the user's home directory
(which may/may not) be mounted via NFS? Will dotlocking work for that?
None of the warnings about .lock files apply when the mailbox file is in the
user's home directory. If that is the case on your system then you can
disregard the entire issue.
Yay! I had been following this issue with some trepidation, as my
situation is that I want to get USER shell processes (like pine) OFF of
the main server where delivery happens, as pine can get kinda hungry when
munching and searching large mailboxes (mine currently shows a 60 meg
footprint in top), and imap may still be attempting to access the mailbox
from the NFS server end, while pine would be accessing it from an NFS
client machine.
I've had it this way even before considering NFS for for several reasons:
easier to manage quotas, easier to scale disks (with a less busy /var to
worry about), plus it gives the user more or less full control on what
they can do with their mailbox (i.e. if one of them stupidly needs to
split it into several files after it got too big, heh), and spanning
multiple disks is as simple as changing the homedirectories (or at worst a
symlink).
Not being able to use this mailbox over nfs would have rendered the
concept of a "shell machine" invalid.
[snip]
On such systems, user mrc's mailbox would be a file, such as
/var/spool/mail/mrc
that is owned by mrc. However, the spool directory (/var/spool/mail) is not
owned by mrc since it is shared by all users. If the spool directory is
protected 1777, then mrc can create /var/spool/mail/mrc.lock and all is good;
Other than the fact that another user can create their own lock files for
all users? Or does file ownership somehow count with dotlocks, i.e. that
the system will ignore the lockfile if it's not owned by the same uid as
the file being locked?
if not, then only by means of a privileged tool such as mlock can mrc create
the /var/spoo/mail/mrc.lock to do this.
Also, is there a primer as to all this somewhere?
There is some discussion of this in the locking.txt documentation file in the
IMAP toolkit. That file is quite old, but there's still a fair amount of
good information in it.
The general information on how .lock files work should be in any good UNIX
sysadmin primer, since it normally applies to all UNIX systems including
those which do not use UW IMAP in any way.
I'd also like to thank you immensely for trying to educate us on all this.
You share a great breadth of experience, and I'm sure you're a busy guy.
-Dan
--
"You're not normal!"
-Michael G. Kessler, referring to my modem online time.
--------Dan Mahoney--------
Techie, Sysadmin, WebGeek
Gushi on efnet/undernet IRC
ICQ: 13735144 AIM: LarpGM
Site: http://www.gushi.org
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