Moving /var/spool/mail

Hi,

Please forgive my ignorance. I have a Linux production server that keeps
running out of space on the /var partition. I wish to move /var/spool/mail
to /home/mail. The box runs sendmail (8.11.6) and the majority of user mail
is picked up via ipop3d (v2001.78rh) though occasionally pine is used by
sysadmins.

To help me with this I would be grateful if anyone could answer the
following questions:

(1) If I just link /var/spool/mail to it's new home would there be a major
performance problem? The box is quite quick and has plenty of RAM. Are there
other hazards to this? Presumably even if I re-pointed sendmail and ipop3d I
could leave "legacy" links for other less frequent users?

(2) If I did just link /var/spool/mail to it's new home what is the best
type of link to use, I have used directory symlinks but know there are also
forced hard links. Which would be best?

(3) I know ipop3d has this option put in at compile time so if I want to
avoid all access through the links I'll have to recompile it but I can't
seem to find an option in sendmail.cf for this either. I have found the
/var/spool/mqueue line but nothing pointing to the /var/spool/mail
directory. Is there any way of doing this?

Thanks very much in advance,

Dave.

On Mon, 19 Dec 2005 14:22:47 -0500, dave <(E-Mail Removed)> wrote:

> Hi,
>
> Please forgive my ignorance. I have a Linux production server that keeps
> running out of space on the /var partition. I wish to move /var/spool/mail
> to /home/mail. The box runs sendmail (8.11.6) and the majority of user mail
> is picked up via ipop3d (v2001.78rh) though occasionally pine is used by
> sysadmins.
>
> To help me with this I would be grateful if anyone could answer the
> following questions:
>
> (1) If I just link /var/spool/mail to it's new home would there be a major
> performance problem? The box is quite quick and has plenty of RAM. Are there
> other hazards to this? Presumably even if I re-pointed sendmail and ipop3d I
> could leave "legacy" links for other less frequent users?
>
> (2) If I did just link /var/spool/mail to it's new home what is the best
> type of link to use, I have used directory symlinks but know there are also
> forced hard links. Which would be best?

You can't hard link across filesystems. I'd just do the soft link and
forget about it. I can't imagine there'd be a problem with that.

On 2005-12-19, dave <(E-Mail Removed)> wrote:
>
> (1) If I just link /var/spool/mail to it's new home would there be a major
> performance problem? The box is quite quick and has plenty of RAM. Are there
> other hazards to this? Presumably even if I re-pointed sendmail and ipop3d I
> could leave "legacy" links for other less frequent users?

There should not be a huge performance hit (if any), and leaving the
link after you reconfigure sendmail and ipop3d is a good idea, in case
someone reads mail using something like Mail or nail.

> (2) If I did just link /var/spool/mail to it's new home what is the best
> type of link to use, I have used directory symlinks but know there are also
> forced hard links. Which would be best?

I've always read that it's a Bad Idea (TM) to use hard links for
directories, but never knew why. Presumably a hard link to a directory
can cause problems for the filesystem or the kernel; the best reference
(which isn't so good, anyway) I've found so far is this thread:

http://lists.debian.org/debian-user/.../msg00333.html

In any case, it sounds like /home and /var are separate filesystems for
your box, so you *must* use a symlink. Hard links only work within one
filesystem.

--keith

--
kkeller-(E-Mail Removed)
(try just my userid to email me)
AOLSFAQ=http://wombat.san-francisco.ca.us/cgi-bin/fom
see X- headers for PGP signature information

Keith Keller wrote:
> I've always read that it's a Bad Idea (TM) to use hard links for
> directories, but never knew why.

Because you have the capacity to create loops in the filesystem: your
recursive commands would never finish unless they had the capability of
detecting the loop.

Paul

On Tue, 20 Dec 2005 02:13:50 -0500, Paul Black <(E-Mail Removed)> wrote:

> Keith Keller wrote:
>> I've always read that it's a Bad Idea (TM) to use hard links for
>> directories, but never knew why.
>
> Because you have the capacity to create loops in the filesystem: your
> recursive commands would never finish unless they had the capability of
> detecting the loop.

Also, on System V, they're very hard to get rid of. I had one once then
deleted it. Every fsck brought it right back.

Paul Black wrote:
> Keith Keller wrote:
>> I've always read that it's a Bad Idea (TM) to use hard links for
>> directories, but never knew why.
>
> Because you have the capacity to create loops in the filesystem: your
> recursive commands would never finish unless they had the capability of
> detecting the loop.
>
> Paul

I thought hard-linking directories was not only inadvisable, but illegal
on most file systems (even within the one file system). To quote from
the man page for ln:

-d, -F, --directory
allow the superuser to attempt to hard link directories (note:
will probably fail due to system restrictions, even for the
superuser)

"David Brown" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...

> I thought hard-linking directories was not only inadvisable, but illegal
> on most file systems (even within the one file system).

And the prisons are already overcrowded as it is.

"gregnoble" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> "David Brown" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
>
>> I thought hard-linking directories was not only inadvisable, but illegal
>> on most file systems (even within the one file system).
>
> And the prisons are already overcrowded as it is.
>
LOL.

Well thanks everyone for their answers.

I haven't heard anybody screaming don't *soft* link /var/spool/mail though
so I'll assume that would be ok?

Cheers,

Dave.

"dave" <(E-Mail Removed)> wrote in message
news:doccm5$ns9$1$(E-Mail Removed)...

> I haven't heard anybody screaming don't *soft* link /var/spool/mail though
> so I'll assume that would be ok?

It's what most administrators do.

gregnoble wrote:
> "dave" <(E-Mail Removed)> wrote in message
> news:doccm5$ns9$1$(E-Mail Removed)...
>
>> I haven't heard anybody screaming don't *soft* link /var/spool/mail though
>> so I'll assume that would be ok?
>
> It's what most administrators do.
>

If you have a spare partition, you could mount it on /var/spool/mail.

For the future, next time you get a new disk, you might want to look
into lvm2, combined with reiserfs file systems. My typical partioning
with linux now is a small boot partition, a root partion (doesn't need
to be too big), and the rest of the disk as a lvm2 physical volume. I
then make logical volumes for things like /home, /usr, and /var, without
worrying too much about sizes. If I run low on space, it's just a
matter of running "lvextend" then "resize_reiserfs" on the partition to
increase its size - it runs in seconds, while the partition is mounted
and in use.