postlock - Man Page

lock mail folder and execute command


postlock [-c config_dir] [-l lock_style]
       [-v] file command...


The postlock(1) command locks file for exclusive access, and executes command. The locking method is compatible with the Postfix UNIX-style local delivery agent.


-c config_dir

Read the configuration file in the named directory instead of the default configuration directory.

-l lock_style

Override the locking method specified via the mailbox_delivery_lock configuration parameter (see below).


Enable verbose logging for debugging purposes. Multiple -v options make the software increasingly verbose.



A mailbox file. The user should have read/write permission.


The command to execute while file is locked for exclusive access.  The command is executed directly, i.e. without interpretation by a shell command interpreter.


The result status is 75 (EX_TEMPFAIL) when postlock(1) could not perform the requested operation.  Otherwise, the exit status is the exit status from the command.


With remote file systems, the ability to acquire a lock does not necessarily eliminate access conflicts. Avoid file access by processes running on different machines.



Directory with Postfix configuration files.


Enable verbose logging for debugging purposes.

Configuration Parameters

The following parameters are especially relevant to this program. The text below provides only a parameter summary. See postconf(5) for more details including examples.

Locking Controls

deliver_lock_attempts (20)

The maximal number of attempts to acquire an exclusive lock on a mailbox file or bounce(8) logfile.

deliver_lock_delay (1s)

The time between attempts to acquire an exclusive lock on a mailbox file or bounce(8) logfile.

stale_lock_time (500s)

The time after which a stale exclusive mailbox lockfile is removed.

mailbox_delivery_lock (see 'postconf -d' output)

How to lock a UNIX-style local(8) mailbox before attempting delivery.

Resource and Rate Controls

fork_attempts (5)

The maximal number of attempts to fork() a child process.

fork_delay (1s)

The delay between attempts to fork() a child process.

Miscellaneous Controls

config_directory (see 'postconf -d' output)

The default location of the Postfix and configuration files.

import_environment (see 'postconf -d' output)

The list of environment parameters that a privileged Postfix process will import from a non-Postfix parent process, or name=value environment overrides.

See Also

postconf(5), configuration parameters


The Secure Mailer license must be distributed with this software.


Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA

Wietse Venema
Google, Inc.
111 8th Avenue
New York, NY 10011, USA

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