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journalctl — Query the systemd journal. See also: `dmesg`. More information: <https://www.freedesktop.org/softwar

Submitted by: @import:tldr-pages·Mar 2, 2026·

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thesystemdcommandcliqueryjournalctljournalsee

linux

Problem

How to use the journalctl command: Query the systemd journal. See also: dmesg. More information: <https://www.freedesktop.org/software/systemd/man/latest/journalctl.html>.

Solution

journalctl — Query the systemd journal. See also: dmesg. More information: <https://www.freedesktop.org/software/systemd/man/latest/journalctl.html>.

Show all messages with priority level 3 (errors) from this boot:

journalctl {{[-b|--boot]}} {{[-p|--priority]}} 3

Delete journal logs which are older than 2 days:

journalctl --vacuum-time 2d

Show only the last n lines and follow new messages (like tail -f for traditional syslog):

journalctl {{[-n|--lines]}} {{n}} {{[-f|--follow]}}

Show all messages by a specific unit:

journalctl {{[-u|--unit]}} {{unit}}

Show logs for a given unit since the last time it started:

journalctl _SYSTEMD_INVOCATION_ID=$(systemctl show --value --property=InvocationID {{unit}})

Filter messages within a time range (either timestamp or placeholders like "yesterday"):

journalctl {{[-S|--since]}} {{now|today|yesterday|tomorrow}} {{[-U|--until]}} "{{YYYY-MM-DD HH:MM:SS}}"

Show all messages by a specific process:

journalctl _PID={{pid}}

Show all messages by a specific executable:

journalctl {{path/to/executable}}

Code Snippets

Show all messages with priority level 3 (errors) from this boot

journalctl {{[-b|--boot]}} {{[-p|--priority]}} 3

Delete journal logs which are older than 2 days

journalctl --vacuum-time 2d

Show only the last `n` lines and follow new messages (like `tail -f` for traditional syslog)

journalctl {{[-n|--lines]}} {{n}} {{[-f|--follow]}}

Show all messages by a specific unit

journalctl {{[-u|--unit]}} {{unit}}

Show logs for a given unit since the last time it started

journalctl _SYSTEMD_INVOCATION_ID=$(systemctl show --value --property=InvocationID {{unit}})

Context

tldr-pages: linux/journalctl

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