System administration

Linux journalctl command

Read systemd journal entries. Use -u to filter by service unit.

Availability: Common Linux commands; shell built-ins and external implementations may differ by distribution.中文

Syntax

journalctl [OPTIONS...] [MATCHES...]

Examples

Show the last 50 SSH unit messages without a pager.

journalctl -u ssh -n 50 --no-pager

Show warning and more severe messages from this boot.

journalctl -b -p warning

Parameters, options and clauses

Option / clause	Description
`-u, --unit=UNIT`	Show messages for a systemd unit.
`-f, --follow`	Follow new journal entries.
`-b, --boot[=ID]`	Show entries from the current boot or a selected boot.
`-n, --lines=N`	Show the most recent N entries.
`--since=TIME / --until=TIME`	Restrict entries to a time range.
`-p, --priority=LEVEL`	Filter by priority and more severe levels.
`--no-pager`	Write output directly instead of opening a pager.

Safety note

Review a command and its target before running it. Commands that alter files, services, accounts, disks, permissions or databases may be difficult to reverse. Test in a safe environment and keep backups.

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