systemd-manager

name	systemd-manager
description	Create and manage systemd services, timers, and socket units. Use when creating background services or daemons, setting up scheduled timers, debugging failed units, viewing unit logs, or managing service dependencies.
category	system
maturity	stable
tags	["systemd","timers","journalctl","unit-files","daemons"]

Systemd Manager Skill

Create and manage systemd services, timers, and socket units.

Use When

• Creating background services or daemons
• Setting up scheduled timers (modern cron alternative)
• Debugging failed units or viewing logs
• Managing service dependencies and ordering

Quick Reference

Service Management

# Start / stop / restart
sudo systemctl start myapp
sudo systemctl stop myapp
sudo systemctl restart myapp
sudo systemctl reload myapp          # reload config without restart

# Enable at boot / disable
sudo systemctl enable myapp
sudo systemctl enable --now myapp    # enable + start

# Status
systemctl status myapp
systemctl is-active myapp
systemctl is-enabled myapp

# List all services
systemctl list-units --type=service
systemctl list-units --type=service --state=failed

# Show unit file
systemctl cat myapp

# Reload after editing unit files
sudo systemctl daemon-reload

Journalctl (Logs)

# Logs for a service
journalctl -u myapp

# Follow (tail -f equivalent)
journalctl -u myapp -f

# Last 100 lines
journalctl -u myapp -n 100

# Since time
journalctl -u myapp --since "1 hour ago"
journalctl -u myapp --since "2024-01-15 09:00"

# Only errors
journalctl -u myapp -p err

# Disk usage / vacuum
journalctl --disk-usage
sudo journalctl --vacuum-size=500M

# Boot logs
journalctl -b         # current boot
journalctl -b -1      # previous boot

# Kernel messages
journalctl -k

Timers (Cron Replacement)

# List active timers
systemctl list-timers --all

# Timer unit example — runs every 15 minutes
# /etc/systemd/system/backup.timer
# [Timer]
# OnCalendar=*:0/15
# Persistent=true

# Calendar expressions:
# *:0/15         → every 15 min
# hourly         → top of every hour
# daily          → midnight
# Mon *-*-* 09:00:00  → Monday 9am
# *-*-01 00:00:00     → 1st of month

# Test calendar expression
systemd-analyze calendar "Mon *-*-* 09:00:00"
systemd-analyze calendar "*:0/15"

Debugging

# Why did it fail?
systemctl status myapp
journalctl -u myapp -n 50 --no-pager

# Dependency tree
systemctl list-dependencies myapp

# Analyze boot time
systemd-analyze blame
systemd-analyze critical-chain myapp.service

# Check unit file syntax
systemd-analyze verify /etc/systemd/system/myapp.service

# Show all properties
systemctl show myapp

Helper Scripts

Generate service unit file

bash scripts/gen-service.sh <name> <exec-start> [--user <user>] [--workdir <dir>] [--env "KEY=VAL"]
# Example: bash scripts/gen-service.sh myapi "/usr/bin/node /opt/myapi/index.js" --user www-data --workdir /opt/myapi

Generate timer unit

bash scripts/gen-timer.sh <name> <calendar-expr> [--description "desc"]
# Example: bash scripts/gen-timer.sh backup "daily" --description "Daily backup"

Check service status summary

bash scripts/status-check.sh [service-name|--failed]

Unit File Patterns

Simple Service

[Unit]
Description=My Application
After=network.target

[Service]
Type=simple
User=myuser
WorkingDirectory=/opt/myapp
ExecStart=/usr/bin/node index.js
Restart=on-failure
RestartSec=5
StandardOutput=journal
StandardError=journal

[Install]
WantedBy=multi-user.target

Service with Environment File

[Service]
EnvironmentFile=/etc/myapp/env
ExecStart=/opt/myapp/bin/server

Oneshot (run once, e.g. for timers)

[Service]
Type=oneshot
ExecStart=/opt/scripts/backup.sh

Timer + Service Pair

# backup.timer
[Unit]
Description=Run backup daily

[Timer]
OnCalendar=daily
Persistent=true
RandomizedDelaySec=300

[Install]
WantedBy=timers.target

# backup.service
[Unit]
Description=Backup job

[Service]
Type=oneshot
ExecStart=/opt/scripts/backup.sh

Hardened Service

[Service]
# Security hardening
ProtectSystem=strict
ProtectHome=true
NoNewPrivileges=true
PrivateTmp=true
ReadWritePaths=/var/lib/myapp
CapabilityBoundingSet=
SystemCallFilter=@system-service

Common Options

Option	Values	Purpose
Type	simple, forking, oneshot, notify	Process type
Restart	no, on-failure, always, on-abnormal	When to restart
RestartSec	5	Delay between restarts
WantedBy	multi-user.target, timers.target	Install target
After	network.target, postgresql.service	Ordering
Requires	postgresql.service	Hard dependency
Wants	redis.service	Soft dependency