Configuring journald in CentOS to make it persistent

Journald’s advantages over other logging systems such as rsyslog is that it is very efficient and logs just about everything on your system automatically without the need to configure anything because it is a part of the systemd suite. The main disadvantage is that all journald log information will get lost after a system’s restart. Journald logging can produce huge amounts of data and by default, all logging information is only kept in memory, which is not very practicable if you need to access older log information or analyze causes of system crash reboots. Here, in this process, we show you how to configure journald to make it persistent.

To Start With: What Do You Need?

To complete this process, you will require a minimal installation of the CentOS 7 operating system with root privileges and a console-based text editor of your choice.

The Process

To begin this process, we need to create a location that will hold our persistent journal database:

1. Log in as the root user and create the following directory:
   mkdir /var/log/journal
2. Next, add the new directory to journald to use it as a storage location and fix permissions:
   systemd-tmpfiles --create --prefix /var/log/journal
3. Now, restart journald:
   systemctl restart systemd-journald
4. Finally, to check whether the log survived the reboot, restart the computer and type the following:
   journalctl --boot=-1

How it works…

We initiated this process by creating the new directory, /var/log/journal. By default, journald writes its log database to /run/log/journal, which is a directory only for runtime information, and its content does not survive system reboots. Afterward, we used the systemd-tmpfiles command to set up our new directory for journald. Finally, we restarted the journald server daemon to apply our changes to the system. To test if persistence is working, restart your server and afterward use journalctl –boot=-1. This will show us all journal information from the last boot. If persistence is not working, it will print out the following error; otherwise, it will correctly show all journal messages before the last boot:
Failed to look up boot -1: Cannot assign requested address

In this fairly simple process, we have shown how to make journald persistent over system reboots. This is really useful if you need to review older log files from the past, which can sometimes help you find out problems, for example, the roots of past hardware failures.