> For the complete documentation index, see [llms.txt](https://book.dragonsploit.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://book.dragonsploit.com/linux/scheduling-jobs.md).

# Scheduling Jobs

## Introduction

When penetration testing Linux systems you may come across a system that is running a job at a regular interval. Sometimes those can be hijacked or otherwise abused. Here I discuss the two main methods, cron jobs and systemd timers.

## Cron

## Systemd Timers

<https://www.youtube.com/watch?v=Oup21KLlpD8>

You need three elements

* Script or program to run
* Systemd service
  * Goes into `/etc/systemd/system` or `/lib/systemd/system/` and ents in `.service`
* Timer to start the service
  * Goes into `/etc/systemd/system/` and ends in `.timer`
  * Timers run the `.service` that shares the same name as it by default
    * This behavior can be changed by adding `Unit=<service name>` in the `[Timer]` section &#x20;

Example Script

```bash
#!/bin/bash
echo "The date is $(date)" >> /tmp/log.log
```

Example Service

```bash
[Unit]
Description=My custom script

[Service]
Type=simple
ExecStart=/opt/myscript.sh
User=arronp
```

Example Timers

```bash
[Unit]
Description=My Custom script

[Timer]
Unit=myscript.service
OnBootSec=5min
OnUnitActiveSec=15min

[Install]
Wantedby=graphical.timer
```

```bash
[Unit]
Description=My Custom script

[Timer]
Unit=myscript.service
OnCalendar=Thu *-*-* 17:00:00

[Install]
Wantedby=timers.target
```

To start the timer once all elements are in place:

```bash
sudo systemctl deamon-reload
sudo systemctl enable myscript.timer
sudo systemctl start myscript.timer
```

## View Timers

You can view all of the timers with:

```bash
systemclt list-timers
```

Continuously look at timers every second with:

```bash
watch -n 1 'systemctl list-timers'
```