Update cheatsheets

tldr/linux/systemctl-is-enabled

@@ -0,0 +1,22 @@
+---
+syntax: markdown
+tags: [tldr, linux]
+source: https://github.com/tldr-pages/tldr.git
+---
+# systemctl is-enabled
+
+> Check whether unit files are enabled.
+> See also: `systemctl enable`, `systemctl disable`.
+> More information: <https://www.freedesktop.org/software/systemd/man/latest/systemctl.html#is-enabled%20UNIT%E2%80%A6>.
+
+- Show the enablement state:
+
+`systemctl is-enabled {{unit1 unit2 ...}}`
+
+- Suppress output and return only the exit code:
+
+`systemctl is-enabled {{unit}} --quiet`
+
+- Show installation targets and symlink paths:
+
+`systemctl is-enabled {{unit}} --full`