Find the name of the systemd unit for MariaDB or RabbitMQ server.
List all installed services, including disabled services, and search for “maria”:
systemctl list-unit-files --type=service | grep maria
Alternative if you know the package name:
$ rpm -ql mariadb-server|grep service /usr/lib/systemd/system/mariadb.service
List enabled services:
Note: it looks like “list-units” doesn’t show mariadb.service, probably because it is disabled (not started at boot).
System logs: journald and journalctl¶
- Show syslog from the most recent to the oldest logs:
- Show all logs since the last boot:
journalctl -b 0
- List boots:
tail -f /var/log/syslog:
tail -f /var/log/syslogbut only for apache:
journalctl -u apache.service -f
- Kernel logs of the current boot:
journalctl -k(similar to
dmesgbut with better timestamp)
- Retain only journald logs of the past 30 days:
journalctl _PID=7797show logs of process pid 7797
Advantages over scattered text log files:
- Timestamps seem to be more reliable, especially for kernel logs
- Ability to display logs in the reverse order
- Ability to filter logs by service, by user, by process pid, by boot, etc.
- … in fact, I rarely use logs, so I don’t have strong expectations for logs :-)
Advantages of systemd to run services¶
- I like systemd global design to build “stateless” services, by isolating them from the system for example.
- Security: systemd gives access to high level security protections like
running a service with its own private temporary directory
- Read also Using systemd for more secure services in Fedora
- systemd can even create a couple of temporary (user, group) to run a service
and remove theme once the service stops. To be able to implement this
feature, systemd has to cleanup all resources owner by the user. Running
the service with a read-only filesystem except of a single writable directory
helps to remove all files created by the service. Removing all IPC owned by
a user is part of this cleanup (option
systemctl status serviceshows the last log lines.
- Thanks to cgroups, systemd is able to list all processes of a service in a
systemctl status servicelists all process identfiers of the service (main pid, but also pids of child processes). Moreover, when systemd stops a service, the usage of a cgroups makes sure that all processes are killed. Bye bye the legacy and annoying “pid file” causing so many troubles.
- The simple
.servicefile format makes it much easier to share these files between Linux distributions. Linux distributions can collaborate on more complex issues like handling properly NFS mounts: Systemd programming, 30 months later. Moreover, it’s easier to enable security protections for all Linux distributions.
There is a similar trend to isolate desktop applications using sandboxes: see Flatpak. For security, but also to reduce dependencies to the system, and so run an old application on a newer system, or the opposite. Embedding libraries in Flatpak “containers” comes with its own set of issues, but that’s a different topic ;-)
systemd features are not unique, it’s totally doable without sytemd.
Right, but systemd comes with a simple configuration files (.service files) which gives an easy access to these features.
systemd has bugs!
Right, as any other software. And they are quickly fixed.
systemd developers reject patches to support platforms other than Linux:
Ok, this is a real issue. I have no answer for that one :-)
BSD systems don’t use systemd but reimplemented the strict minimum systemd APIs required by Gnome.