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Re: bin/38103: automounter (amd) failed to unmount busy filesystems on reboot - reboot will hang
The following reply was made to PR bin/38103; it has been noted by GNATS.
From: christos%zoulas.com@localhost (Christos Zoulas)
To: gnats-bugs%NetBSD.org@localhost, gnats-admin%netbsd.org@localhost,
Subject: Re: bin/38103: automounter (amd) failed to unmount busy filesystems on
reboot - reboot will hang
Date: Thu, 28 Feb 2008 14:38:46 -0500
On Feb 28, 5:00pm, tron%zhadum.org.uk@localhost (Matthias Scheler) wrote:
-- Subject: Re: bin/38103: automounter (amd) failed to unmount busy filesyste
| The following reply was made to PR bin/38103; it has been noted by GNATS.
| From: Matthias Scheler <tron%zhadum.org.uk@localhost>
| To: gnats-bugs%NetBSD.org@localhost
| Subject: Re: bin/38103: automounter (amd) failed to unmount busy filesystems
on reboot - reboot will hang
| Date: Thu, 28 Feb 2008 16:59:02 +0000
| On Wed, Feb 27, 2008 at 10:21:14AM -0500, Christos Zoulas wrote:
| > | Anyway, I've backed out the change to "/etc/rc.d/amd" already.
| > | amd(8) is a lost cause and should be removed from NetBSD as
| > | soon as possible.
| > Great attitude here, "hands hurts: cut it off". I am using amd on ~500
| > machines here and it works just fine.
| I'm using it for a long time, too. But I wouldn't say it works fine:
| 1.) If I run "build.sh" with the source and object directory on a
| amd(8) mount point the automounter daemon consumes upto 20% of the
| CPU time (on a 1.87GHz Xeon 30xx CPU).
Yes, because you are constantly traversing the automounted path which is
is by default not cached. Trying doing 'tcpdump localhost port nfs' :-)
To avoid that you can refer only to relative paths, or set in the global
section of amd.conf:
auto_attrcache = 1
Which will cache for 1 second. Save some CPU trees.
| 2.) The lack of support for direct mounts is a big problem. A lot
| of programs use realpath(3) and end up trying to use directory names
| like "/export/home/<user>" (on the server) or
| "/amd/<server>/export/home/<user>" (on the client). Quite frequently
| such pathnames end up in configuration files which now don't work
| if you switch between the server, the client or a machine with
| a proper automounter (e.g. Solaris or Linux).
Yes, that is indeed a problem. I don't have this issue at work because
I mount everything under the same namespace, both on the client and the
and I use /u/<name> -> /net/<hostname>/<partition-name>/<name> for user home
dir mounts for example. I've also use shells that do symbolic path traversal
and alias pwd to pawd. But the direct mount will be fixed once I complete
some autofs work that I have been postponing for~ever.
| > What's the alternative, don't cross mount between machines?
| No, but we should replace it with something that is actually working
| properly. The shutdown issue is not the only problem, see above.
| I've talked to Antti Kantee and it seems that a "puffs" based automounter
| wouldn't have the shutdown problems.
It will be a lot slower, and you'll be dealing with the same race conditions
amd has to deal with, only re-discovering them :-)
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