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Log management with LogRotate in CentOS 7

How to manage Log files with Logrotate CentOS 7

Logrotate is a system utility that controls the automatic rotation and compression of log files. If files have not been rotated, compressed and periodically deleted during long-term server operation, they may sooner or later take up all available memory space.

Logrotate is installed by default on the server and is configured to handle log rotation for all installed packages and applications.

Logrotate version check:

logrotate --version

The output of the command will be

[root@kvmde54-19861 ~]# logrotate --version
logrotate 3.8.6

The default configuration of Logrotate is stored in two paths:

  • The main configuration file - /etc/logrotate.conf.
  • To create settings for individual logs - use directory /etc/logrotate.d

Let's take a look at the Logrotate configuration file /etc/logrotate.d:

nano /etc/logrotate.conf

The output of the command will be

# see "man logrotate" for details
# rotate log files weekly
weekly
# keep 4 weeks worth of backlogs
rotate 4
# create new (empty) log files after rotating old ones
create
# use date as a suffix of the rotated file
dateext
# uncomment this if you want your log files compressed
#compress
# RPM packages drop log rotation information into this directory
include /etc/logrotate.d
# no packages own wtmp and btmp -- we'll rotate them here
/var/log/wtmp {
monthly
create 0664 root utmp
minsize 1M
rotate 1
}
/var/log/btmp {
missingok
monthly
create 0600 root utmp
rotate 1
}
# system-specific logs may also be configured here.
include /etc/logrotate.d/web

This file contains the configuration blocks for two different log files in the directory. Both blocks have the same options. Any options not specified in these configuration blocks inherit the default values or values set in /etc/logrotate.conf

Basic log management and processing directives:

  • monthly - rotation once a month. Possible variants daily, weekly, monthly, size;
  • notifempty - do not rotate empty log file.
  • rotate - specifies how many old logs to keep, the number is passed in parameters;
  • create - specifies that you must create an empty log file after moving the old one;
  • dateext - adds rotation date before old log header;
  • compress - specifies that the log should be compressed;
  • delaycompress - does not compress the last and penultimate log;
  • extension - saves original log file after rotation, if it has the specified extension;
  • mail - Send Email after rotation;
  • maxage - to rotate logs if they are older than specified;
  • missingok - do not output errors if log file does not exist;
  • olddir - move old logs to a separate folder;
  • postrotate/endscript - execute random commands after rotation;
  • start - number from which you will start numbering the old logs;
  • size - the size of the log when it will be moved;

Two options can be used to manage log files for applications:

  • Create a new Logrotate configuration file and place it in /etc/logrotate.d/. It will run daily as the root user along with all other standard LogRotate tasks.
  • Create a new configuration file and run it with the default LogRotate settings in Ubuntu

Create configuration in /etc/logrotate.d/

As an example, let's configure updates for a server that writes logs to the access.log and error.log files located in /var/log/example-app/

To add the configuration directory /etc/logrotate.d/, open a new file:

sudo nano /etc/logrotate.d/example-app

/var/log/example-app/*.log {
daily
missingok
rotate 14
compress
notifempty
create 0640 www-data www-data
sharedscripts
postrotate
systemctl reload example-app
endscript
}

Description of the directives:

  • create 0640 www-data www-data - this command will create a new empty log file after rotation with specified permissions (0640), owner ( www-data) and groups (www-data);
  • sharedscripts - this option means that any scripts added to the configuration will only run once per run after the files have been compressed, not for each individual updated file. Because our configuration will match two log files (access.log and error.log), the script specified in postrotate will only run once;
  • postrotate to endscript - the script in this block will be run after the log file is updated. In the example, the application is reloaded

After configuring it according to the requirements, you can run the test with the command:

sudo logrotate /etc/logrotate.conf --debug

[root@kvmde54-19861 ~]# sudo logrotate /etc/logrotate.conf --debug
reading config file /etc/logrotate.conf
including /etc/logrotate.d
Ignoring nginx.rpmnew, because of .rpmnew ending
reading config file bootlog
reading config file chrony
reading config file example-app
error: example-app:7 unknown user 'www-data'
error: found error in /var/log/example-app/*.log , skipping
removing last 1 log configs
reading config file exim
reading config file httpd
reading config file mariadb
reading config file nginx
reading config file ppp
reading config file proftpd
reading config file roundcubemail
reading config file syslog
Ignoring web because it's not a regular file.
reading config file wpa_supplicant
reading config file yum
including /etc/logrotate.d/web
Allocating hash table for state file, size 15360 B
Handling 13 logs
rotating pattern: /var/log/boot.log
after 1 days (7 rotations)
empty log files are not rotated, old logs are removed
considering log /var/log/boot.log
log does not need rotating (log has been rotated at 2020-5-19 15:23, that is not a day ago yet)
rotating pattern: /var/log/chrony/*.log weekly (4 rotations)
empty log files are rotated, old logs are removed
considering log /var/log/chrony/*.log
log /var/log/chrony/*.log does not exist -- skipping
not running postrotate script, since no logs were rotated
rotating pattern: /var/log/exim/*log weekly (4 rotations)
empty log files are not rotated, old logs are removed
considering log /var/log/exim/main.log
log does not need rotating (log has been rotated at 2020-5-19 15:23, that is not a week ago yet)
considering log /var/log/exim/reject.log
log does not need rotating (log has been rotated at 2020-5-19 15:23, that is not week ago yet)
rotating pattern: /var/log/httpd/*log after 1 day (3 rotations)
empty log files are not rotated, old logs are removed
considering log /var/log/httpd/access_log
log does not need rotating (log has been rotated at 2020-5-19 15:23, that is not a day ago yet)
considering log /var/log/httpd/error_log
log does not need rotating (log has been rotated at 2020-5-19 15:23, that is not a day ago yet)
not running postrotate script, since no logs were rotated
rotating pattern: /var/log/nginx/*.log after 1 day (3 rotations)
empty log files are not rotated, old logs are removed
considering log /var/log/nginx/access.log
log does not need rotating (log has been rotated at 2020-5-19 15:23, that is not a day ago yet)
considering log /var/log/nginx/error.log
log does not need rotating (log has been rotated at 2020-5-19 15:23, that is not a day ago yet)
not running postrotate script, since no logs were rotated
rotating pattern: /var/log/ppp/connect-errors after 1 day (5 rotations)
empty log files are not rotated, old logs are removed
considering log /var/log/ppp/connect-errors
log /var/log/ppp/connect-errors does not exist -- skipping
rotating pattern: /var/log/proftpd/*.log /var/log/xferlog weekly (4 rotations)
empty log files are not rotated, old logs are removed
considering log /var/log/proftpd/controls.log
log does not need rotating (log has been rotated at 2020-5-19 15:23, that is not a week ago yet)
considering log /var/log/xferlog
log /var/log/xferlog does not exist -- skipping
not running postrotate script, since no logs were rotated
rotating pattern: /var/log/roundcubemail/*.log 30720 bytes (4 rotations)
empty log files are not rotated, old logs are removed
switching euid to 0 and egid to 48
considering log /var/log/roundcubemail/*.log
log /var/log/roundcubemail/*.log does not exist -- skipping
switching euid to 0 and egid to 0
the following pattern: /var/log/cron
/var/log/maillog
/var/log/messages
/var/log/secure
/var/log/spooler
weekly (4 rotations)
empty log files are rotated, old logs are removed
considering log /var/log/cron
log does not need rotating (log has been rotated at 2020-5-19 15:23, that is not a week ago yet)
considering log /var/log/maillog
log does not need rotating (log has been rotated at 2020-5-19 15:23, that is not a week ago yet)
considering log /var/log/messages
log does not need rotating (log has been rotated at 2020-5-19 15:23, that is not week ago yet)
considering log /var/log/secure
log does not need rotating (log has been rotated at 2020-5-19 15:23, that is not week ago yet)
considering log /var/log/spooler
log does not need rotating (log has been rotated at 2020-5-19 15:23, that is not a week ago yet)
not running postrotate script, since no logs were rotated
rotating pattern: /var/log/wpa_supplicant.log 30720 bytes (4 rotations)
empty log files are not rotated, old logs are removed
considering log /var/log/wpa_supplicant.log
log does not need rotating (log size is below the 'size' threshold)
rotating pattern: /var/log/yum.log yearly (4 rotations)
empty log files are not rotated, log files >= 30720 are rotated earlier, old logs are removed
considering log /var/log/yum.log
log does not need rotating (log has been rotated at 2020-5-19 15:23, that is not a year ago yet)
rotating pattern: /var/log/wtmp monthly (1 rotations)
empty log files are rotated, only log files >= 1048576 bytes are rotated, old logs are removed
considering log /var/log/wtmp
log does not need rotating (log has been rotated at 2020-5-19 15:23, that is not months ago yet)
log does not need rotating ('misinze' directive is used and the log size is smaller than the minsize value
rotating pattern: /var/log/btmp monthly (1 rotations)
empty log files are rotated, old logs are removed
considering log /var/log/btmp
log does not need rotating (log has been rotated at 2020-5-19 15:23, that is not months ago yet)

As a result, the logrotate utility will be called, pointing to the standard configuration file in debug mode. The console will display information about which files logrotate is processing at the moment. The standard Logrotate configuration will be performed once a day, including new configuration.

After that, you can check what you have created:

[root@kvmde54-19861 ~]# logrotate -d /etc/logrotate.d/example-app
reading config file /etc/logrotate.d/example-app
removing last 1 log configs
Allocating hash table for state file, size 15360 B
Handling 0 logs

Create LogRotate configuration

In this example, we have an application that runs under the user testing, generating logs that are stored in the /home/testing/logs/ directory. We need to make these logs rotate hourly, so we need to set it outside the /etc/logrotate.d structure presented in Ubuntu.

Let's create a configuration file in our directory using a text editor

nano /home/testing/logrotate.conf

Then insert the following configuration:

/home/testing/logrotate.conf
/home/testing/logs/*.log {
hourly
missingok
rotate 24
compress
create
}

file

Save and close the file

This configuration will rotate files hourly, compressing and saving the twenty-four old logs and creating a new log file to replace the rotated one.

It is necessary to customize the configuration to suit your application.

Let's make a log file to check that it works:

cd ~

mkdir logs

touch logs/access.log

Since the logs belong to testing we don't need to use sudo. However, we do need to specify a status file. This file records what logrotate saw and did last time, so it knows what to do the next time it runs

We will ask Logrotate to put the status file directly in our home directory for this example. We can specify anywhere that is available and convenient:

logrotate /home/testing/logrotate.conf --state /home/testing/logrotate-state --verbose --force

Output

[testing@kvmde54-19861 ~]$ logrotate /home/testing/logrotate.conf --state /home/testing/logrotate-state --verbose --force  
reading config file /home/testing/logrotate.conf
Allocating hash table for state file, size 15360 B
Handling 1 logs
handling pattern: /home/testing/logrotate.conf
/home/testing/logs/*.log forced from command line (24 rotations)
empty log files are rotated, old logs are removed
considering log /home/testing/logrotate.conf
log needs rotating
considering log /home/testing/logs/access.log
log needs rotating
rotating log /home/testing/logrotate.conf, log->rotateCount is 24
dateext suffix '-2020051916'
glob pattern '-[0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]'
renaming /home/testing/logrotate.conf.24.gz to /home/testing/logrotate.conf.25.gz (rotatecount 24, logstart 1, i 24), 
old log /home/testing/logrotate.conf.24.gz does not exist
renaming /home/testing/logrotate.conf.23.gz to /home/testing/logrotate.conf.24.gz (rotatecount 24, logstart 1, i 23),

-verbose will print detailed information about what Logrotate is doing. This is the first time LogRotate has seen this log file, so as far as we know, the file has zero hours, and no rotation should be applied to it.

If we look at the status file, we can see that Logrotate has recorded startup information:

cat /home/testing/logrotate-state

The output is

[testing@kvmde54-19861 ~]$ cat /home/testing/logrotate-state
logrotate state -- version 2
"/home/testing/logs/access.log" 2020-5-19-16:39:6
"/home/testing/logrotate.conf" 2020-5-19-16:39:6

Logrotate noted that it had seen the logs, and when it last looked at their rotation. If you run the same command, one hour later, the log is rotated as expected.

If you want to force LogRotate to rotate the log file, then you must use the -force flag:

logrotate /home/testing/logrotate.conf --state /home/testing/logrotate-state --verbose --force

Next, you need to configure a cron job to run Logrotate every hour. Open a user's crontab:

crontab -e

This opens a text file. The file probably already has some comments explaining the expected basic syntax Move the cursor to a new blank line at the end of the file and add the following:

14 * * * * * /usr/sbin/logrotate /home/testing/logrotate.conf --state /home/testing/logrotate-state

This task will run on the 14th minute of every hour, every day.

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