add systemd,core,ptrace_scope

1 files changed, 68 insertions, 0 deletions

diff --git a/src/linux/systemd.md b/src/linux/systemd.md
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+++ b/src/linux/systemd.md
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+# systemd
+
+## systemctl
+
+Inspect units:
+```text
+systemctl [opts] [cmd]
+[opts]
+    --user
+
+[cmd]
+    list-units <pattern>    List units in memory
+
+    status <unit>           Show runtime status of unit
+
+    start <unit>            Start a unit
+    stop <unit>             Stop a unit
+    restart <unit>          Restart a unit
+    reload <unit>           Reload a unit
+
+    enable <unit>           Enable a unit (persistent)
+    disable <unit>          Disable a unit
+
+    cat <unit>      Print unit file
+    show <unit>     Show properties of unit
+```
+
+### Example: Trivial user unit
+
+```bash
+# Generate unit
+mkdir -p ~/.config/systemd/user
+echo '[Unit]
+Description=Test logger
+
+[Service]
+Type=oneshot
+ExecStart=logger "Hello from test unit"' > ~/.config/systemd/user/test.service
+
+# Run unit
+systemctl --user start test
+
+# See log message
+journalctl --user -u test -n 5
+```
+
+## journalctl
+
+Inspect journal logs:
+```text
+journalctl [opts] [matches]
+    --user          Current user journal (system by default)
+    -u <unit>       Show logs for specified <unit>
+    -n <lines>      Show only last <lines>
+    -f              Follow journal
+    -g <pattern>    Grep for <pattern>
+```
+
+Cleanup:
+```text
+journalctl [opts]
+    --disk-usage            Show current disk usage
+    --vacuum-size=<size>    Reduce journal log to <size> (K/M/G)
+```
+
+## References
+- [man systemd.unit(5)](https://www.man7.org/linux/man-pages/man5/systemd.unit.5.html)
+- [man systemd.service(5)](https://www.man7.org/linux/man-pages/man5/systemd.service.5.html)