If you manage a Koha Library Management System, you will eventually run into a "500 Internal Server Error" or a screen that simply won't load. When this happens, the Koha error logs are the best assistant. The Linux system records events like a personal diary. It tells exactly what went wrong and where.
The most efficient way to watch these errors in real time is to use the tail command in the Linux terminal. Here are simple instructions on how to do it.
Location of the log files
In a standard Koha installation (on Debian or Ubuntu), the logs are stored in /var/log/koha/. Inside that folder, each "instance" (your library's specific setup) has its own directory.
The most important log file is usually plack-error.log or koha-error.log.
The general path looks like this: /var/log/koha/instancename/plack-error.log
Before using the command, find the Koha instance name. The following command will help you find the instance name.
sudo koha-list
Using the tail command
The tail command shows you the last few lines of a file. This is perfect for logs because the newest errors are always added to the bottom.
To see the last 20 lines
If you just want a quick snapshot of the recent activity, type:
sudo tail -n 20 /var/log/koha/library/plack-error.log
To watch errors live (The "-f" switch)
This is the most helpful tool for troubleshooting. The -f stands for follow. It keeps the file open and updates your screen the exact second a new error occurs.
sudo tail -f /var/log/koha/library/plack-error.log
While this command is running, go to your Koha staff interface and refresh the page that is causing the error. You will see the technical details pop up instantly in your terminal.
When you are finished reading the logs and want to go back to the regular command prompt, simply press Ctrl + C
Reading logs might seem confusing at first, but it is the fastest way to fix Koha issues. Instead of guessing why a page isn't working, use tail -f and let the system tell you exactly what is broken.
