Update cheatsheets

tldr/linux/systemctl-list-units

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+---
+syntax: markdown
+tags: [tldr, linux]
+source: https://github.com/tldr-pages/tldr.git
+---
+# systemctl list-units
+
+> List units that systemd currently has in memory.
+> See also: `systemctl list-unit-files` for listing installed unit files.
+> More information: <https://www.freedesktop.org/software/systemd/man/latest/systemctl.html#list-units%20PATTERN%E2%80%A6>.
+
+- List units which are active, have pending jobs, or have failed:
+
+`systemctl list-units`
+
+- List all units, including inactive ones:
+
+`systemctl list-units {{[-a|--all]}}`
+
+- Filter by unit type:
+
+`systemctl list-units {{[-t|--type]}} {{service|socket|timer|...}}`
+
+- Filter by state:
+
+`systemctl list-units --state {{running|listening|dead|...}}`
+
+- Filter by a name pattern:
+
+`systemctl list-units 'systemd*'`
+
+- Print output directly to `stdout`:
+
+`systemctl list-units --no-pager`
+
+- Print output without headers or footers (for scripts):
+
+`systemctl list-units --no-legend`