# SystemD

SystemD is an [init system](/wiki/linux/init.md) for Linux systems.
It is used for service configuration and startup.

## Usage

### Run Command on Boot

To run a command (in this case `/bin/bash /root/run.sh`) create the following
file at `/etc/systemd/system/` with a name ending on `.service`.
In this case it is called `unturned.service`.
Alternatively to creating the command manually the following command can be used.
The `--user` flag may be useful as explained in the
[corresponding section](#startstopenabledisable-a-service-and-retrieve-its-logs).

```sh
systemctl edit --force --full unturned.service
```

And set the contents to the following.

```txt
[Unit]
Description=Description of the service

[Install]
WantedBy=multi-user.target

[Service]
ExecStart=/bin/bash /root/run.sh
Type=simple
```

For [Proxmox](/wiki/linux/proxmox.md) you can add the following line under the `[Unit]` section to
make sure the service is started after Proxmox has finished initializing.

```txt
After=pve-guests.service
```

A service that was created this way can then be started as explained in
[the corresponding section](#startstopenabledisable-a-service-and-retrieve-its-logs).

### Start/Stop/Enable/Disable a service and Retrieve its Logs

Services can be started by running `systemctl start <service-name>`.
They respectively can be stopped by replacing the `start` keyword for `stop`.
To start the service after boot it has to be enabled.
This works accordingly with the keyword `enable`.
The `disable` keyword stops the service from starting automatically.

Logs of the last start of the service can be found by running `systemctl status <service-name>`.

Additionally, the `--user` flag can be set to start the service only for the current user.

### Retrieving the SystemD Logs

SystemD logs can easily be found using the `journalctl` command.
One of the most notable usages of the command is for checking the logs of the previous boot.
This can be achieved by running the following command.

```sh
journalctl -b-1
```

### Change Suspend and Hibernate Behavior

The behavior of suspend and hibernation can be changed in the file `/etc/systemd/sleep.conf`.
One of the most important variables is the one to set the hibernation delay time.
This time will be used to determine the time that is taken from suspend to hibernation if
suspend-to-hibernate is called.
The following line will set this to 10 minutes.

```txt
HibernateDelaySec=10min
```

### Handle Power Key and Lid Switching

The management of power keys and lid switches is handled in the file `/etc/systemd/logind.conf`.
The following line will set the behavior of the power key to hibernate. The default for this would
be to shutdown the system.

```txt
HandlePowerKey=hibernate
```

The same can also be done to determine the action taken when the lid is closed.
By default the closing of the lid will result in suspending the system.
The following lines will change this to suspend-then-hibernate.

```txt
HandleLidSwitch=suspend-then-hibernate
```

For further behavior of the suspend and hibernate actions check the
[corresponding section](#change-suspend-and-hibernate-behavior).

When wanting to work with a closed lid some of the settings in the config file have to be set to
ignore.
As [machetie writes on Reddit](https://www.reddit.com/r/framework/comments/185035i/how_to_use_the_laptop_with_lid_closed_linux/)
the following settings need to be set.

```txt
HandleLidSwitch=ignore
HandleLidSwitchExternalPower=ignore
HandleLidSwitchDocked=ignore
```

Afterward, the logind service has to be restarted
[as described on a later section](#startstopenabledisable-a-service-and-retrieve-its-logs).

```sh
sudo systemctl restart systemd-logind
```

## Troubleshooting

This section focusses on errors that correspond to the SystemD software.

### Timed Out Waiting for Device `/dev/tpmrm0`

This error signals problems with the trusted platform module.
This however usually can be fixed easily by masking the service and is done like the following
command shows.

```sh
systemctl mark dev-tpmrm0.device
```