Transient Units

# Run a command as a transient service
sudo systemd-run --unit=cleanup --scope /usr/bin/cleanup.sh

# Run with resource limits
sudo systemd-run --unit=limited --scope \
    --property=MemoryMax=512M \
    --property=CPUQuota=50% \
    /opt/myapp/bin/heavy-task

# Run in background
sudo systemd-run --unit=background-task --scope --no-block \
    /opt/myapp/bin/long-task

# Run as specific user
sudo systemd-run --unit=user-task --scope \
    --uid=www-data --gid=www-data \
    /usr/bin/check-permissions

# List transient units
systemctl list-units --type=service --state=running | grep cleanup

# Check status
systemctl status cleanup.service

# Stop a transient unit
sudo systemctl stop cleanup.service

# Create a scope for existing processes
sudo systemd-run --scope --unit=mygroup.slice \
    --property=MemoryMax=2G \
    --property=CPUQuota=200% \
    bash -c "echo $$ && sleep 3600"

# List scopes
systemctl list-units --type=scope

# Check scope properties
systemctl show mygroup.slice -p MemoryMax
# MemoryMax=2147483648

# Kill a scope
sudo systemctl kill mygroup.slice

# Remove a scope
sudo systemctl stop mygroup.slice
sudo systemctl reset-failed mygroup.slice

# Scopes for container runtimes
# Docker and containerd use scopes to group container processes
systemctl list-units --type=scope | grep docker
# docker-12345abc.scope

# Run a command periodically
sudo systemd-run --unit=cleanup --scope --on-active=1h \
    /usr/bin/cleanup.sh

# Run at specific time
sudo systemd-run --unit=report --scope --on-calendar="Mon *-*-* 09:00:00" \
    /usr/bin/generate-report.sh

# Run with persistent timer
sudo systemd-run --unit=backup --scope \
    --on-calendar=daily \
    --property=Persistent=true \
    /usr/bin/backup.sh

# List transient timers
systemctl list-timers --all | grep cleanup

# Check timer status
systemctl status cleanup.timer

# Create user service directory
mkdir -p ~/.config/systemd/user/

# Create a user service
cat > ~/.config/systemd/user/myapp.service << 'EOF'
[Unit]
Description=My User Application

[Service]
ExecStart=/usr/bin/myapp
Restart=on-failure

[Install]
WantedBy=default.target
EOF

# Manage user services
systemctl --user daemon-reload
systemctl --user enable myapp.service
systemctl --user start myapp.service
systemctl --user status myapp.service

# List user services
systemctl --user list-units --type=service

# Enable lingering (start services at boot)
sudo loginctl enable-linger $(whoami)

# Check lingering status
loginctl show-user $(whoami) -p Linger
# Linger=yes

# One-shot command with resource limits
sudo systemd-run --scope --property=MemoryMax=1G \
    python3 /opt/scripts/analyze.py

# Run a command and get its output
sudo systemd-run --unit=output-test --scope -- \
    /bin/bash -c "echo 'hello' > /tmp/test.txt && cat /tmp/test.txt"

# Timer for a one-time future task
sudo systemd-run --unit=reminder --scope \
    --on-calendar="2024-01-15 14:00:00" \
    /bin/notify-send "Task reminder"

# Run with specific working directory
sudo systemd-run --unit=dir-test --scope \
    --property=WorkingDirectory=/opt/myapp \
    ./run-tests.sh

# Group processes for resource control
sudo systemd-run --scope --unit=batch-group.slice \
    --property=CPUQuota=100% \
    --property=MemoryMax=2G \
    bash -c "for i in {1..10}; do ./task.sh & done; wait"