Add basic linux troubleshooting tips

docs/source/docs/troubleshooting/index.md

@@ -7,4 +7,5 @@ common-errors
 logging
 camera-troubleshooting
 networking-troubleshooting
+unix-commands
 ```

docs/source/docs/troubleshooting/unix-commands.md

@@ -0,0 +1,61 @@
+Useful Unix Commands
+====================
+
+SSH
+---
+
+[SSH (Secure Shell)](https://www.mankier.com/1/ssh) is used to securely connect from a local to a remote system (ex. from a laptop to a coprocessor). Unlike other commands on this page, ssh is not Unix specific and can be done on Windows and MacOS from their respective terminals.
+
+:::{note}
+You may see a warning similar to `The authenticity of host 'xxx' can't be established...` or `WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!`, in most cases this can be safely ignored if you have confirmed that you are connecting to the correct host over a secure connection, and the fingerprint will change when your operating system is reinstalled or PhotonVision's coprocessor image is re-flashed. You can read more about it [here](https://superuser.com/questions/421997/what-is-a-ssh-key-fingerprint-and-how-is-it-generated)
+:::
+
+Example:
+
+:::{code-block}
+ssh username@hostname
+:::
+
+ip
+--
+
+Run [ip address](https://www.mankier.com/8/ip) with your coprocessor connected to a monitor in order to see its IP address and other network configuration information.
+
+
+SCP
+---
+
+[SCP (Secure Copy)](https://www.mankier.com/1/scp) is used to securely transfer files between local and remote systems.
+
+Example:
+
+:::{code-block}
+scp [file] username@hostname:/path/to/destination
+:::
+
+v4l2-ctl
+--------
+
+[v4l2-ctl](https://www.mankier.com/1/v4l2-ctl) is a command-line tool for controlling video devices.
+
+List available video devices (used to verify the device recognized a connected camera):
+
+:::{code-block}
+v4l2-ctl --list-devices
+:::
+
+List supported formats and resolutions for a specific video device:
+
+:::{code-block}
+v4l2-ctl --list-formats-ext --device /path/to/video_device
+:::
+
+List all video device's controls and their values:
+
+:::{code-block}
+v4l2-ctl --list-ctrls --device path/to/video_device
+:::
+
+:::{note}
+This command is especially useful in helping to debug when certain camera controls, like exposure, aren't behaving as expected. If you see an error in the logs similar to `WARNING 30: failed to set property [property name] (UsbCameraImpl.cpp:646)`, that means that PhotonVision is trying to use a control that doesn't exist or has a different name on your hardware. If you encounter this issue, please [file an issue](https://github.com/PhotonVision/photonvision/issues) with the necessary logs and output of the `v4l2-ctl --list-ctrls` command.
+:::