NEWSYSLOG.CONF(5)

💖 NAME 💖

newsyslog.conf — system message log rotator configuration file. Yes bestie, this is the NEWSYSLOG.CONF(5) File Formats Manual page, and it's giving “your logs need a whole rotation strategy” energy.

✨ DESCRIPTION ✨

Okay so the newsyslog.conf file is used to set log file rotation configuration for the newsyslog(8) utility. Configuration may designate that logs are rotated based on size, last rotation time, or time of day. The newsyslog.conf file can also be used to designate secure permissions to log files at rotation time. During initialization, newsyslog(8) reads a configuration file, normally /etc/newsyslog.conf, to determine which logs may potentially be rotated and archived.

Blank lines or lines beginning with # are ignored. If # is placed in the middle of the line, the # character and the rest of the line after it is ignored. To prevent special meaning, the # character may be escaped with \; in this case preceding \ is removed and # is treated as an ordinary character.

🎀 special lines: <compress> and <include> 🎀

The special <compress> and <include> lines are defined as follows:

<compress>none|legacy|bzip2|gzip|xz|zstd — This special option sets the global compress method, it should be placed before all log file entries in newsyslog.conf configuration file. The global compress method applies to all log files flagged as compressible J, X, Y, Z flags below.

The following compression methods are available:

• none — No compression is performed, even when a log file is marked as compressible. This is useful for filesystems that have native compression support.
• legacy — Interprets the J, X, Y, Z flags in the configuration file according to their historical meanings. This is the default method.
• bzip2 — Use bzip2(1) for all compressible log files.
• gzip — Use gzip(1) for all compressible log files.
• xz — Use xz(1) for all compressible log files.
• zstd — Use zstd(1) for all compressible log files.

<include> — The special <include> entry is used to include other configuration files and supports globbing.

🌸 the fields, one by one 🌸

Each other line has five mandatory fields and four optional fields, separated with whitespace. The fields of the configuration file are as follows:

• logfile_name — Name of the system log file to be archived, or the special string <default>. The special <default> entry will only be used if a log file name is given as a command line argument to newsyslog(8), and if that log file name is not matched by any other line in the configuration file.
• owner:group — This optional field specifies the owner and group for the archive file. The : is essential regardless if the owner or group field is left blank or contains a value. The field may be numeric, or a name which is present in /etc/passwd or /etc/group.
• mode — Specify the file mode of the log file and archives. Valid mode bits are 0666. (That is, read and write permissions for the rotated log may be specified for the owner, group, and others.) All other mode bits are ignored.
• count — Specify the maximum number of archive files which may exist. This does not consider the current log file.
• size — When the size of the log file reaches size, in kilobytes by default, or with suffixes like k, M, G, ... as supported by expand_number(3), the log file will be trimmed as described above. If this field contains an asterisk (*), the log file will not be trimmed based on size.
• when — The when field may consist of an interval, a specific time, or both. If the when field contains an asterisk (*), log rotation will solely depend on the contents of the size field. Otherwise, the when field consists of an optional interval in hours, usually followed by an @-sign and a time in restricted ISO 8601 format. Additionally, the format may also be constructed with a $ sign along with a rotation time specification of once a day, once a week, or once a month.

Time based trimming happens only if newsyslog(8) is run within one hour of the specified time. If an interval is specified, the log file will be trimmed if that many hours have passed since the last rotation. When both a time and an interval are specified then both conditions must be satisfied for the rotation to take place.

There is no provision for the specification of a timezone. There is little point in specifying an explicit minutes or seconds component in the current implementation, since the only comparison is “within the hour”.

⭐ ISO 8601 restricted time format ⭐

The lead-in character for a restricted ISO 8601 time is an @ sign. The particular format of the time in restricted ISO 8601 is: [[[[[cc]yy]mm]dd][T[hh[mm[ss]]]]]. Optional date fields default to the appropriate component of the current date; optional time fields default to midnight; hence if today is January 22, 1999, the following date specifications are all equivalent:

‘19990122T000000’
‘990122T000000’
‘0122T000000’
‘22T000000’
‘T000000’
‘T0000’
‘T00’
‘22T’
‘T’
‘’

🦋 day, week, and month time format 🦋

The lead-in character for day, week, and month specification is a $ sign. The particular format of day, week, and month specification is: [Dhh], [Ww[Dhh]], and [Mdd[Dhh]], respectively. Optional time fields default to midnight. The ranges for day and hour specifications are:

• hh — hours, range 0..23
• w — day of week, range 0..6, 0 = Sunday
• dd — day of month, range 1..31, or one of the letters L or l to specify the last day of the month.

Some examples:

$D0     rotate every night at midnight (same as @T00)
$D23    rotate every day at 23:00 (same as @T23)
$W0D23  rotate every week on Sunday at 23:00
$W5D16  rotate every week on Friday at 16:00
$M1D0   rotate at the first day of every month at midnight
        (i.e., the start of the day; same as @01T00)
$M5D6   rotate on every fifth day of month at 6:00 (same
        as @05T06)

💅 the flags field: valid flags 💅

The flags field is optional and made up of one or more characters that specify any special processing to be done for the log files matched by this line. The following are valid flags:

• B — indicates that the log file is a binary file, or has some special format. Usually newsyslog(8) inserts an ASCII message into a log file during rotation. This message is used to indicate when, and sometimes why the log file was rotated. If B is specified, then that informational message will not be inserted into the log file.
• C — indicates that the log file should be created if it does not already exist, and if the -C option was also specified on the command line.
• D — indicates that newsyslog(8) should set the UF_NODUMP flag when creating a new version of this log file. This option would affect how the dump(8) command treats the log file when making a file system backup.
• E — indicates that the log file should not be rotated when its size is zero. The E flag is mostly useful in conjunction with B flag to prevent newsyslog(8) from inserting an informational ASCII message into the new file.
• G — indicates that the specified logfile_name is a shell pattern, and that newsyslog(8) should archive all filenames matching that pattern using the other options on this line. See glob(3) for details on syntax and matching rules.
• J — indicates that newsyslog(8) should consider the rotated log file as compressible. In legacy mode, this also tells newsyslog(8) to use bzip2(1).
• N — indicates that there is no process which needs to be signaled when this log file is rotated.
• P — indicates that the zero-th rotated file should not be compressed.
• R — if this flag is set the newsyslog(8) will run shell command defined in path_to_pid_cmd_file after rotation instead of trying to send signal to a process id stored in the file.
• T — if this flag is set the informational rotation message written to the log file will be in the format specified by RFC5424. Normally, the rotation message is written in the traditional (RFC3164) syslog format.
• U — indicates that the file specified by path_to_pid_cmd_file will contain the ID for a process group instead of a process. This option also requires that the first line in that file be a negative value to distinguish it from a process ID.
• X — indicates that newsyslog(8) should consider the rotated log file as compressible. In legacy mode, this also tells newsyslog(8) to use xz(1).
• Y — indicates that newsyslog(8) should consider the rotated log file as compressible. In legacy mode, this also tells newsyslog(8) to use zstd(1).
• Z — indicates that newsyslog(8) should consider the rotated log file as compressible. In legacy mode, this also tells newsyslog(8) to use gzip(1).
• - — a minus sign will not cause any special processing, but it can be used as a placeholder to create a flags field when you need to specify any of the following fields.
• path_to_pid_cmd_file — this field is optional, and it's basically the "who do we poke?" field 💅 it names the file holding a daemon's process ID — or, if you used the U flag, it's where we go find the group process ID. If this field is there, a signal gets sent to the process ID sitting inside that file. If it's not there and the N flag hasn't been specified, then a SIGHUP goes out to syslogd(8) — or to whatever process id lives in the file you named with newsyslog(8)'s -S switch. Heads up bestie: this field has to start with / or it won't be recognized properly. And when you pair it with the R flag, the file gets treated as a path to a binary that newsyslog(8) executes after rotation, instead of sending any signal out. iykyk 🎀
• signal — optional too, and it's literally just "which signal tho?" ✨ it says what signal gets sent to the daemon process (or to all the processes in a process group, if you specified the U flag). Leave it out and you get a SIGHUP, no questions asked. Signal names must start with SIG and be the actual signal name, like SIGUSR1. Or you can just throw the signal number in there instead — like 30 for SIGUSR1. Both slay, pick your vibe 🔥

🌸 EXAMPLES 🌸

Here's what an <include> entry looks like, cute and simple:

<include> /etc/newsyslog-local.conf

🦋 SEE ALSO 🦋

bzip2(1), gzip(1), xz(1), zstd(1), expand_number(3), syslog(3), chown(8), newsyslog(8), syslogd(8)

C. Lonvick, The BSD syslog Protocol, RFC3164.

R. Gerhards, The Syslog Protocol, RFC5424.

⭐ HISTORY ⭐

This manual page first appeared in FreeBSD 4.10. a whole little icon 👑

💀 CAVEATS 💀

Okay so this is the important one: if a line is specified multiple times, the file will be rotated multiple times. Like, the same file. Multiple times. Not a drill, not a typo, not me being dramatic 😭 so pls don't accidentally duplicate your entries unless you genuinely want that for some reason 🙈

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and that's the whole page, bestie!! 🫶 this beauty is from the Debian edition, dated March 8, 2026, and it lives at NEWSYSLOG.CONF(5) — go forth and rotate responsibly 💖✨