How To Manage Logfiles with Logrotate

From WickyWiki


See also: Systemd logging

Systemd logging aims to be better than syslog. Usually both Systemd and Syslog are available on the system. You might consider looking into it:

Sent log message from shell script: 

#-p [severity 0-7] 0=emergency, 2=error, 6=info, 7=debug
echo "[wjv backup] backup error message" | systemd-cat -t "identifier" -p 2

Syslog

To prevent your log files from growing without limit the 'logrotate' command can be used to specify what you want to keep. There are a lot of options and you might want to integrate your log-cleaning into the daily logrotate schedule.

More info here:

Complete info can be found on the man page: 

man logrotate

Independent configuration

This example is limited to an independent configuration and some basic options.

Create logrotate config file: 

sudo nano /home/user1/logs/example.conf
/home/user1/logs/*.log {
    rotate 4
    daily
    size 10k
    create
    compress
    delaycompress
}

This file will be ignored if it hasn't the correct permissions. Permissions that work are 'all=read' (444) OR 'user/owner=read/write, group and other=read' (644): 

chmod u=rw,g=r,o=r /home/user1/logs/example.conf

Options explained:

Option Meaning
rotate 4 Keep 4 archived logfiles (1-4), older files are disposed of
daily Rotate not more than once a day, the state-file is used to check if the logfile was rotated earlier today.
size 1k Do not rotate if the logfile size is less than 1k
missingok Do not report an error if the logfile does not exist
compress Compress (gz) rotated logfiles
delaycompress Compress the last archived logfile with the next rotation (2-4 will be compressed)
notifempty Do not rotate if the logfile is empty
create Create new empty logfile after rotation

Manually logrotate

Option -v (verbose) is added so you can see what is happening. 

logrotate -v /home/user1/logs/example.conf --state /home/user1/logs/logrotate-state

Add to daily crontab

The time that was used here is daily at 4:04 am. 

nano /etc/crontab
 04 04 * * * *  /usr/sbin/logrotate /home/user1/logs/example.conf --state /home/user1/logs/logrotate-state

System settings and locations for logrotate

Linux allows you to use the general logging and logrotate process. It will help if you use the standard files and locations to reduce the complexity of your app.

Start-off with placing your app-logs in your own app directory under /var/log/ 

mkdir /var/log/yourapp

A logfile could be /var/log/yourapp/yourapp.log

Sytem logrotate default settings can be found in the file /etc/logrotate.conf you don't have to edit this file. The file /etc/logrotate.conf will include all configuration files in the directory /etc/logrotate.d/. You should place 'yourapp' logrotate configuration in that directory in a new file. 

nano /etc/logrotate.d/yourapp
/var/log/yourapp/*.log {
    daily
    missingok
    rotate 7
}
chmod u=rw,g=r,o=r /etc/logrotate.d/yourapp

Rotating will not be done more that once a day as it will be part of a daily crontab job. The log status for all the logs (name,date and time) will be kept in a single file: 

cat /var/lib/logrotate/status

Empty a logfile as admin

Clear: 

echo "" | sudo tee /var/log/logfile.log
cat /var/log/logfile.log

Append (-a): 

echo "append this line" | sudo tee -a /var/log/logfile.log
Retrieved from "https://wjv.duckdns.org/mediawiki/index.php?title=How_To_Manage_Logfiles_with_Logrotate&oldid=3272"