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diff --git a/README_FILES/MAILLOG_README b/README_FILES/MAILLOG_README new file mode 100644 index 0000000..ec63b96 --- /dev/null +++ b/README_FILES/MAILLOG_README @@ -0,0 +1,113 @@ +PPoossttffiixx llooggggiinngg ttoo ffiillee oorr ssttddoouutt + +------------------------------------------------------------------------------- + +OOvveerrvviieeww + +Postfix supports it own logging system as an alternative to syslog (which +remains the default). This is available with Postfix version 3.4 or later. + +Topics covered in this document: + + * Configuring logging to file + * Configuring logging to stdout + * Rotating logs + * Limitations + +CCoonnffiigguurriinngg llooggggiinngg ttoo ffiillee + +Logging to file solves a usability problem for MacOS, and eliminates multiple +problems for systemd-based systems. + + 1. Add the following line to master.cf if not already present (note: there + must be no whitespace at the start of the line): + + postlog unix-dgram n - n - 1 postlogd + + Note: the service type "uunniixx--ddggrraamm" was introduced with Postfix 3.4. Remove + the above line before backing out to an older Postfix version. + + 2. Configure Postfix to write logging, to, for example, /var/log/postfix.log. + See also the "Logfile rotation" section below for logfile management. + + # postfix stop + # postconf maillog_file=/var/log/postfix.log + # postfix start + + By default, the logfile name must start with "/var" or "/dev/stdout" (the + list of allowed prefixes is configured with the maillog_file_prefixes + parameter). This safety mechanism limits the damage from a single + configuration mistake. + +CCoonnffiigguurriinngg llooggggiinngg ttoo ssttddoouutt + +Logging to stdout is useful when Postfix runs in a container, as it eliminates +a syslogd dependency. + + 1. Add the following line to master.cf if not already present (note: there + must be no whitespace at the start of the line): + + postlog unix-dgram n - n - 1 postlogd + + Note: the service type "uunniixx--ddggrraamm" was introduced with Postfix 3.4. Remove + the above line before backing out to an older Postfix version. + + 2. Configure main.cf with "maillog_file = /dev/stdout". + + 3. Start Postfix with "ppoossttffiixx ssttaarrtt--ffgg". + +RRoottaattiinngg llooggss + +The command "ppoossttffiixx llooggrroottaattee" may be run by hand or by a cronjob. It logs all +errors, and reports errors to stderr if run from a terminal. This command +implements the following steps: + + * Rename the current logfile by appending a suffix that contains the date and + time. This suffix is configured with the maillog_file_rotate_suffix + parameter (default: %Y%m%d-%H%M%S). + + * Reload Postfix so that postlogd(8) immediately closes the old logfile. + + * After a brief pause, compress the old logfile. The compression program is + configured with the maillog_file_compressor parameter (default: gzip). + +Notes: + + * This command will not rotate a logfile with a pathname under the /dev + directory, such as /dev/stdout. + + * This command does not (yet) remove old logfiles. + +LLiimmiittaattiioonnss + +Background: + + * Postfix consists of a number of daemon programs that run in the background, + as well as non-daemon programs for local mail submission or Postfix + management. + + * Logging to the Postfix logfile or stdout requires the Postfix postlogd(8) + service. This ensures that simultaneous logging from different programs + will not get mixed up. + + * All Postfix programs can log to syslog, but not all programs have + sufficient privileges to use the Postfix logging service, and many non- + daemon programs must not log to stdout as that would corrupt their output. + +Limitations: + + * Non-daemon Postfix programs will log errors to syslogd(8) before they have + processed command-line options and main.cf parameters. + + * If Postfix is down, the non-daemon programs postfix(1), postsuper(1), + postmulti(1), and postlog(1), will log directly to $maillog_file. These + programs expect to run with root privileges, for example during Postfix + start-up, reload, or shutdown. + + * Other non-daemon Postfix programs will never write directly to + $maillog_file (also, logging to stdout would interfere with the operation + of some of these programs). These programs can log to postlogd(8) if they + are run by the super-user, or if their executable file has set-gid + permission. Do not set this permission on programs other than postdrop(1) + and postqueue(1). + |