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logadm - manage endlessly growing log files
logadm
logadm [-options] logname...
logadm is a general log rotation tool that is suitable for running from cron(1M).
Without arguments, logadm reads the /etc/logadm.conf file, and for every entry found in that file checks the corresponding log file to see if it should be rotated. Typically this check is done each morning by an entry in the root's crontab.
If the logname argument is specified, logadm renames the corresponding log file by adding a suffix so that the most recent log file ends with .0 (that is, logfile.0), the next most recent ends with .1 (that is, logfile.1), and so forth. By default, ten versions of old log files are kept (that is, logfile.0 through logfile.9). At the point when what would be the eleventh file is logged, logadm automatically deletes the oldest version to keep the count of files at ten.
logadm takes a number of options. You can specify these options on the command line or in the /etc/logadm.conf file. The logadm command searches /etc/logadm.conf for lines of the form logname options
logname
options
If options are specified both in /etc/logadm.conf and on the command line, those in the /etc/logadm.conf file are applied first. Therefore, the command line options override those in /etc/logadm.conf.
Log file names specified in /etc/logadm.conf may contain filename substitution characters such as * and ?, that are supported by csh(1).
Two options control when a log file is rotated. They are: -s size -p period.
When using more than one of these options at a time, there is an implied and between them. This means that all conditions must be met before the log is rotated.
If neither of these two options are specified, the default conditions for rotating a log file are: -s 1b -p 1w, which means the log file is only rotated if the size is non-zero and if at least 1 week has passed since the last time it was rotated.
By specifying -p never as a rotation condition, any other rotation conditions are ignored and logadm moves on to the expiration of old log files. By specifying -p now as a rotation condition, a log rotation is forced.
Unless specified by the -o, -g, or -m options, logadm replaces the log file (after renaming it) by creating an empty file whose owner, group ID, and permissions match the original file.
Three options control when old log files are expired: -A age -C count -S size. These options expire the oldest log files until a particular condition or conditions are met. For example, the combination -C 5 and the -S 10m options expires old log files until there are no more than 5 of the and their combined disk usage is no more than 10 megabytes. If none of these options are specified, the default expiration is -C 10 which keeps ten old log files. If no files are to be expired, use -C 0 to prevent expiration by default.
The following options are supported:
-a post_command
Specify post_command as a valid shell command. Use quotes to protect spaces or shell metacharacters in post_command.
This option can be used to restart a daemon that is writing to the file. When rotating multiple logs with one logadm command, post_command is executed only once after all the logs are rotated, not once per rotated log.
-A age
Specify age as a number followed by an h (hours), d (days), w(weeks), m (months), or y (years).
-b pre_command
Specify pre_command as a valid shell command. Use quotes to protect spaces or shell metacharacters in the pre_command.
This option can be used to stop a daemon that is writing to the file. When rotating multiple logs with one logadm command, pre_command is executed only once before all the logs are rotated, not once per rotated log.
-c
-C count
If no expire options (-A, -C, or -S) are specified, -C 10 is the default. To prevent the default expire rule from being added automatically, specify -C 0 .
-e mail_addr
As logadm is typically run from cron(1M), error messages are captured by cron and mailed to the owner of the crontab.
This option is useful if you want the mail regarding error messages to go to another address instead. If no errors are encountered, no mail message is generated.
-E cmd
cmd is passed it to sh -c. The file is considered expired after cmd completes. If the old log file is not removed or renamed by the cmd, logadm considers it for expiration the next time that it runs on the specified log file. If present, the keyword $file is expanded in the specified cmdto the name of the file being expired.
This option is useful for tasks such as mailing old log files to administrators, or copying old log files to long term storage.
-f conf_file
This option allows non-root users to keep their own logadm configuration files.
-g group
Specify group by name or by numeric group ID, as accepted by chgrp(1).
This option requires the ability to change file group ownership using the chgrp(1) command.
-h
-l
-m mode
Specify mode in any form that is accepted by the chmod(1) command.
-M cmd
-n
This option is useful for checking arguments before making any changes to the system.
It is important to remember, however, that since log rotating actions are only printed with this option, logadm might not find files that need expiring, but if run without the -n logadm might create a file that needs expiring by performing the log rotating actions. Therefore, if you see no files being expired with the -n option, files still might be expired without it.
-N
-o owner
Specify owner in any form that is accepted by the chown(1) command.
-p period
Specify period as a number followed by d for days, h for hours, w for weeks, m for months (30 days) or y for years. There are also two special values for period: now and never. "-p now" forces log rotation. "-p never" forces no log rotation.
-P timestamp
This option uses timestamp to determine if the log rotation period has passed. The format of timestamp matches the format generated by ctime(3C), with quotes around it to protect embedded spaces. timestamp is always recorded in the Coordinated Universal Time (UTC) timezone.
-r
-R cmd
This option is useful for processing log file contents after rotating the log. cmd is executed by passing it to sh -c. When rotating multiple logs with one logadm command, the command supplied with -R is executed once every time a log is rotated. This is useful for post-processing a log file (that is, sorting it, removing uninteresting lines, etc.). The -a option is a better choice for restarting daemons after log rotation.
-s size
Specify size as a number followed by the letter b for bytes, k for kilobytes, m for megabytes, or g for gigabytes.
-S size
Specify size as a number followed by the letter b for bytes, k for kilobytes, m for megabytes, or g for gigabytes.
-t template
template can be a simple name, such as /var/adm/oldfile, or it can contain special keywords which are expanded by logadm and are in the form $word. Allowed sequences are:
$basename
$dirname
$domain
$file
$isa
$machine
$n
$N
$nodename
$platform
$release
$secs
$zonename
To actually have the dollar sign character in the file name, use $$. Any percent sequences allowed by strftime(3C) are also allowed, for example, %d expands to the day of the month. To actually have a percent sign character in the file name, use %%. Both dollar-sign keywords and percent sequences can appear anywhere in the template. If the template results in a pathname with non-existent directories, they are created as necessary when rotating the log file.
If no -t option is specified, the default template is $file.$n. Actual rotation of log files, where each version is shifted up until it expires is done using the $n keyword. If the template does not contain the $n keyword, the log file is simply renamed to the new name and then the expire rules, if any, are applied.
-T pattern
This option is useful if another program fiddles with the old log file names, like a cron job to compress them over time. The pattern is in the form of a pathname with special characters such as * and ? as supported by csh(1) filename substitution.
-v
-V
This option validates that an entry for the specified logname exists in the /etc/logadm.conf file and is syntactically correct. If logname is not specified, all entries in the configuration file are validated. If a logname argument is specified, the command validates the syntax of that entry. If the entry is found, it is printed and the exit value of the command is true. Otherwise the exit value is false.
-w entryname
If no log file name is provided on a logadm command line, the entry name is assumed to be the same as the log file name. For example, the following two lines achieve the same thing, keeping two copies of rotated log files:
% logadm -C2 -w mylog /my/really/long/log/file/name % logadm -C2 -w /my/really/long/log/file/name
-z count
The compression is done with gzip(1) and the resulting log file has the suffix of .gz.
The following operands are supported:
logname
Example 1 Rotating a File and Keeping Previous Versions
The following example rotates the /var/adm/exacct/proc file, keeping ten previous versions in /var/adm/exacct/proc.0 through /var/adm/exacct/proc.9.
Tell logadm to copy the file and truncate it.
% logadm -c /var/adm/exacct/proc
Example 2 Rotating syslog
The following example rotates syslog and keeps eight log files. Old log files are put in the directory /var/oldlogs instead of /var/log:
% logadm -C8 -t'/var/oldlogs/syslog.$n' /var/log/syslog
Example 3 Rotating /var/adm/sulog and Expiring Based on Age
The following entry in the /etc/logadm.conf file rotates the /var/adm/sulog file and expires any copies older than 30 days.
/var/adm/sulog -A 30d
Example 4 Rotating Files and Expiring Based on Disk Usage
The following entry in the /etc/logadm.conf file rotates the /var/adm/sulog file and expires old log files when more than 100 megabytes are used by the sum of all the rotated log files.
/var/adm/sulog -S 100m
Example 5 Creating an Entry that Stores the Logfile Name
This example creates an entry storing the log file name and the fact that we want to keep 20 copies in /etc/logadm.conf, but the -p never means the entry is ignored by the normal logadm run from root's crontab every morning.
% logadm -w locallog /usr/local/logfile -C20 -p never
Use the following entry on the command line to override the -p never option:
% logadm -p now locallog
Example 6 Rotating the apache Error and Access Logs
The following example rotates the apache error and access logs monthly to filenames based on current year and month. It keeps the 24 most recent copies and tells apache to restart after renaming the logs.
This command is run once, and since the -w option is specified, an entry is made in /etc/logadm.conf so the apache logs are rotated from now on.
% logadm -w apache -p 1m -C 24\
-t '/var/apache/old-logs/$basename.%Y-%m'\
-a '/usr/apache/bin/apachectl graceful'\
'/var/apache/logs/*{access,error}_log'
This example also illustrates that the entry name supplied with the -w option doesn't have to match the log file name. In this example, the entry name is apache and once the line has been run, the entry in /etc/logadm.conf can be forced to run by executing the following command:
% logadm -p now apache
Because the expression matching the apache log file names was enclosed in quotes, the expression is stored in /etc/logadm.conf, rather than the list of files that it expands to. This means that each time logadm runs from cron it expands that expression and checks all the log files in the resulting list to see if they need rotating.
The following command is an example without the quotes around the log name expression. The shell expands the last argument into a list of log files that exist at the time the command is entered, and writes an entry to /etc/logadm.conf that rotates the files.
logadm -w apache /var/apache/logs/*_log
/etc/logadm.conf
See attributes(5) for descriptions of the following attributes:
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chgrp(1), chmod(1), chown(1), csh(1), gzip(1), cron(1M), ctime(3C), strftime(3C), logadm.conf(4), attributes(5)
When logadm applies expire conditions (supplied by the -A, -C, and -S options), it deletes files, the oldest first, until the conditions are satisfied. If the template used for naming the old logs contained $n or $N, logadm picks the highest value of $n or $N found in the old log file names first. If the template used is something else, logadm uses the modification time to determine which files to expire first. This may not be the expected behavior if an old log file has been modified since it was rotated.
Depending on log file sizes and number of log files, log file rotations can be very time-consuming.
By default, logadm works in GMT. Therefore, all entries written to the /etc/logadm.conf file (see logadm.conf(4)) will have a GMT timestamp. Users can use the -l option to set logadm to local time.
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