newsyslog.confnewsyslog(8) configuration file

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

Name of the system log file to be archived, or the literal 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.
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. By default, log files are owned by root:admin.
Specify the file mode of the log file and archives.
Specify the maximum number of archive files which may exist. This does not consider the current log file.
When the size of the log file reaches size in kilobytes, 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.
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.

If a time is specified, the log file will only be trimmed 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”.


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

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:

hours, range 0..23
day of week, range 0..6, 0 = Sunday
day of month, range 1..31, or one of the letters ‘L’ or ‘l’ to specify the last day of the month.

Some examples:

rotate every night at midnight (same as @T00)
rotate every day at 23:00 (same as @T23)
rotate every week on Sunday at 23:00
rotate every week on Friday at 16:00
rotate at the first day of every month at midnight (i.e., the start of the day; same as @01T00)
rotate on every 5th day of month at 6:00 (same as @05T06)
This optional field is 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:
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.
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.
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.
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.
indicates that newsyslog(8) should attempt to save disk space by compressing the rotated log file using bzip2(1).
indicates that there is no process which needs to be signaled when this log file is rotated.
indicates that the file specified by path_to_pid_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.
indicates that newsyslog(8) should attempt to save disk space by compressing the rotated log file using 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.
This optional field specifies the file name containing a daemon's process ID or to find a group process ID if the U flag was specified. If this field is present, a signal_number is sent the process ID contained in this file. If this field is not present, then a SIGHUP signal will be sent to syslogd(8), unless the N flag has been specified. This field must start with ‘/’ in order to be recognized properly.
This optional field specifies the signal number that will be sent to the daemon process (or to all processes in a process group, if the U flag was specified). If this field is not present, then a SIGHUP signal will be sent.

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

This manual page first appeared in FreeBSD 4.10.

November 27, 2006 macOS 14.4