dovecot - May 2011 - How to stop mail_executable from cwd to ~home

In our environment home directories are auto-mounted via /home/<user>
including on the server provided mail.
Within the various mail services though we try to isolate
and override with local /mail/home/<user>

Works well except that dovecot still wants to cd to the real home
triggering a useless and potentially hindering automount
when it invokes the imap or pop3 process specified by mail_executable,
ie an lsof of the process shows cwd of /home/<user> and the automounted
home.

It does this even though home is properly overridden within.
I suspect this is part of changing to invoke as the user
as the *-login process are ok but then they are still running as dovecot.
Various recent attempts to explicitly respecify HOME for mail_executable
via a wrapper script or using env have been to no avail
(as seen below).

How can I resolve?
And no I don't just want to override /home at the system level.
Thanks
	-- Gary

# 1.0.9: /etc/dovecot.conf
base_dir: /var/run/dovecot/
syslog_facility: local1
protocols: imap imaps pop3 pop3s
listen(default): *:143
listen(imap): *:143
listen(pop3): *:110
ssl_listen(default): *:993
ssl_listen(imap): *:993
ssl_listen(pop3): *:995
ssl_ca_file: /etc/ssl/certs/gd_bundle.crt
ssl_cert_file: /etc/ssl/certs/engr.uvic.ca.crt
ssl_key_file: /etc/ssl/private/engineeringwildcard.key
ssl_parameters_regenerate: 24
disable_plaintext_auth: no
login_dir: /var/run/dovecot/login
login_executable(default): /usr/libexec/dovecot/imap-login
login_executable(imap): /usr/libexec/dovecot/imap-login
login_executable(pop3): /usr/libexec/dovecot/pop3-login
login_log_format_elements: %u [%r] %c
login_process_size: 32
login_processes_count: 8
login_max_processes_count: 150
verbose_proctitle: yes
first_valid_uid: 100
default_mail_env:
mbox:/mail/home/%u/mail/:INBOX=/mail/boxes/%u:INDEX=/mail/indexes/%u
mail_location:
mbox:/mail/home/%u/mail/:INBOX=/mail/boxes/%u:INDEX=/mail/indexes/%u
mbox_read_locks: fcntl dotlock
mbox_write_locks: fcntl dotlock
mail_executable(default): /bin/env 'HOME=/mail/home/$USER'
/usr/libexec/dovecot/imap
mail_executable(imap): /bin/env 'HOME=/mail/home/$USER'
/usr/libexec/dovecot/imap
mail_executable(pop3): /usr/libexec/dovecot/pop3-home
mail_plugin_dir(default): /usr/lib/dovecot/imap
mail_plugin_dir(imap): /usr/lib/dovecot/imap
mail_plugin_dir(pop3): /usr/lib/dovecot/pop3
imap_client_workarounds(default): delay-newmail outlook-idle netscape-eoh
tb-extra-mailbox-sep
imap_client_workarounds(imap): delay-newmail outlook-idle netscape-eoh
tb-extra-mailbox-sep
imap_client_workarounds(pop3): outlook-idle
pop3_uidl_format(default): 
pop3_uidl_format(imap): 
pop3_uidl_format(pop3): %v.%u
pop3_client_workarounds(default): 
pop3_client_workarounds(imap): 
pop3_client_workarounds(pop3): oe-ns-eoh outlook-no-nuls
auth default:
  passdb:
    driver: pam
  userdb:
    driver: passwd
    args: home=/mail/home/%u
plugin:
  home: /mail/home/%u

On Wed, 2011-05-18 at 17:45 -0700, Gary Duncan wrote:
> Works well except that dovecot still wants to cd to the real home
> triggering a useless and potentially hindering automount
> when it invokes the imap or pop3 process specified by mail_executable,
> ie an lsof of the process shows cwd of /home/<user> and the
automounted home.
> 
> How can I resolve?
> # 1.0.9: /etc/dovecot.conf
..
>   userdb:
>     driver: passwd
>     args: home=/mail/home/%u
Upgrade to v1.1+ and this home setting will actually work.

Gary Duncan <gduncan at engr.UVic.CA> writes:
> In our environment home directories are auto-mounted via /home/<user>
> including on the server provided mail.
> Within the various mail services though we try to isolate
> and override with local /mail/home/<user>
>
> Works well except that dovecot still wants to cd to the real home
> triggering a useless and potentially hindering automount
This becomes really apparent if you have an organization wide-mailing
list, and one delivery to it causes a flurry of automounts.  I similarly
replace per-user mounts with a home mount bundle.
> when it invokes the imap or pop3 process specified by mail_executable,
> ie an lsof of the process shows cwd of /home/<user> and the
automounted home.
I see the same behaviour in 2.0.13, which process tracing of imap
shows more clearly (/nfs/user is per user mount, /nfs/home/user
is user home bundle)

 	...
 	4087:   getuid()                                        = 12345 [12345]
 	4087:   chdir("/nfs/test")                              = 0
 	4087:   stat64("/nfs/home/test/mail", 0xFFBFF6C0)       = 0
 	4087:   stat64("/nfs/home/test/mail", 0xFFBFF5A0)       = 0
 	4087:   stat64("/nfs/home/test/mail", 0xFFBFF6C0)       = 0
 	...

This happens fairly early after imap-login forks and execs the imap
process.  I'll see if I can find it after building a debug version,
but I think Timo will beat me to this.

Joseph Tam <jtam.home at gmail.com>

Timo wrote:
>> As to how to stop the mail process from chdir'ing to a home
directory
>
> If you don't want Dovecot to use a home directory, don't tell it a
home directory.
I'm all for that since I don't seem to have any need for a home
directory.
Any idea of how to do it with a passwd-file userdb backend?  I also
tried to override home directory with

 	userdb {
 		driver = passwd-file
 		args = /etc/passwd home=/bundled/home/$n
 	}

but that didn't work out too well.  Or is this feature a rephrasing of
the current topic thread "Global fields for passwd-file database".

Joseph Tam <jtam.home at gmail.com>