Are variables supported in logrotate configuration files?

Question

I looked at logrotate.conf examples and everything in my /etc/logrotate.d directory. Nowhere was I able to find documentation on variables in these files.

I am trying to create a config file for rotating the logs of an application we are writing. I want to set the directory where logs are stored once, and then use it as a variable, like so:

my_app_log_dir=/where/it/is/deployed/logs

${my_app_log_dir}/*.log ${my_app_log_dir}/some_sub_dir/*.log {
    missingok
    # and so on
    # ...
}

Is that possible?

Femineity

Answer 1

You can achieve what you are looking for by implementing this kludge:

my-logrotate.conf ( NOTE: double quotes " are mandatory, also note that file names don't have to appear on the same line )

"*.log"
"some_sub_dir/*.log"
{
    missingok
    # and so on
    # ...
}

Then the actual logrotate script - my-logrotate.sh

#!/bin/sh

set -eu

cd "${my_app_log_dir}"
exec logrotate /path/to/my-logrotate.conf

Now you can add logrotate.sh to your crontab.

Teferi

Answer 2

You can use a bash "here document" to create a suitable config file on the fly, either at installation time or before running logrotate.

A bash script might look like this:

cat >rt.conf <<.
"${my_app_log_dir}/*.log" {
    rotate 5
    size 15k
    missingok
}
.

logrotate  rt.conf

Majors

Answer 3

Directly in the config file no (as far as my knowledge in logrotate goes).

Other solution:

• Use the include option to include parts of the configuration file from a directory. This can help you if you have a package for your application, the package can leave a file in that directory containing only the entries for your app.

Cilicia

Answer 4

With logrotate 3.8.7,a test reveals that you can set and use variables in the pre-rotate and post-rotate script sections.

I tried this for a particular service log file.

   postrotate
         pid_file="/run/some_service/some_serviced.pid"
         test -e "${pid_file}" && kill -s HUP $(cat "${pid_file}") || true
         touch "${pid_file}.WAS_USED"
   endscript

After running logrotate in force mode to ensure the log file was rotated and the post-rotate script executed, on looking in /run/some_service, there was an additional file "some_serviced.pid.WAS_USED", thus proving that the use of the variable worked.

Latoyalatoye

Answer 5

Another option - probably not the cleanest - is to have a placeholder in the logrotate.conf file, which can be replaced on installation time for the real directory.

logrotate.conf :

(...)
XX_APP_LOG_DIR_XX/*.log {
(...)
}

Then you would have in your installation.sh something like:

sed -i "s/XX_APP_LOG_DIR_XX/$my_app_log_dir/" $CNF_DIR/logrotate.conf

If permissions are an issue, you can choose not to put the logrotate.conf in /etc/logrotate.d, but in any other directory. In such case you would have to call logrotate yourself, specifying your conf file:

logrotate $CNF_DIR/logrotate.conf

Euphemiah