Systemd and Journalctl are modern tools for Linux admins now a days. In this post I am trying to capture important details for quick understanding.
Systemd is an init system and system manager recently adopted by Linux systems. Definition from linux manual -
systemd is a system and service manager for Linux operating systems.
When run as first process on boot (as PID 1), it acts as init system
that brings up and maintains userspace services. Separate instances
are started for logged-in users to start their services.
systemd is usually not invoked directly by the user, but is installed as the /sbin/init symlink and started during early boot.
Commands which can help
systemctl status kubelet.service
systemctl start kubelet.service
systemctl stop kubelet.service
systemctl reload kubelet.service
systemctl restart kubelet.service
systemctl enable kubelet.service
systemctl is-active kubelet.service
systemctl is-enabled kubelet.service
systemctl list-units -all
systemctl list-unit-files | grep service | grep enabledsystemctl list-units --type=service# config filesystemctl cat kubelet.service# dependencies systemctl list-dependencies kubelet.service
One of the main benefit behind the
systemd journal is to centralize the management of logs regardless of where the messages are originating. With
systemd all the system, boot, and kernel log files are collected and managed by a central, dedicated logging solution. The
journald daemon collects data from all available sources and stores them in a binary format for easy and dynamic manipulation.
More Details on
Linux system logging changed with the introduction of systemd.
journalctl command can be used to read and filter system logs.
journalctl may be used to query the contents of the systemd(1)
journal as written by systemd-journald.service(8). If called without parameters, it will show the full contents of the journal, starting with the oldest entry collected.
To view the logs that the
journald daemon has collected, use the
# to view the logs of current boot
journalctl -b # list boots
Logs can be filters by unit as well.
systemctl list-units -all | grep -i kubelet.service# once you get your service you can check the logs journalctl -u kubelet.servicejournalctl -u kubelet.service --since today# by process idjournalctl _PID=16852# control the number of lines or entries journalctl -n 30# tail logsjournalctl -f
That’s All for this post. I will update this post again if I get any important update. Thanks.