autofs-standby

Monitors the state of an autofs share and puts USB hubs into standby mode whenever possible.

⚠️ Please note: This is an experimental prototype for my very specific setup (Raspberry Pi 4 + Fantec QB-35US3R (4 x 3.5") RAID). If you inted to use this with your own setup, make sure not to power-off any USB devices while performing critical operations.

Installation

Prerequisites

1. Download and install https://github.com/mvp/uhubctl (make sure you can turn the correct USB hub on and off)
2. Install autofs: sudo apt install autofs

Configure AutoFS

1. Create the directory where the share is mounted: sudo mkdir /autofs
2. Adjust the uuid of the drive to ./auto.vault.sh (can be checked with sudo lsblk -f)
3. Copy the files ./auto.vault and ./auto.vault.sh to /etc and chown them to root
4. Add the following line to /etc/auto.master: /autofs program:/etc/auto.vault.sh --timeout=300 --ghost (make sure there is an empty line at the end of the config, otherwise the daemon will not load properly)
5. Restart autofs: sudo service autofs restart

Create a Standby Watchdog Service

1. Copy standby_watchdog.service to /etc/systemd/system/: sudo cp standby_watchdog.service /etc/systemd/system/
2. Start the service: sudo systemctl start standby_watchdog
3. Start the service on boot: sudo systemctl enable standby_watchdog
4. Register a service to run standby_watchdog.py in the background

Testing / Troubleshooting

1. Check if USB can be powered on and off using uhubctl:
   1. power on: sudo uhubctl -l 1-1 -a on
   2. power off: sudo uhubctl -l 1-1 -a off
2. Access the share: ls -la /autofs/vault
3. Monitor standby_watchdog.service to see if the mounted share is detected.
4. Wait the timeout specified in auto.vault.sh and try to access the share again.
5. Wait the timeout specified in standby_watchdog.py (SLEEP_DURATION * STANDBY_COUNT seconds) to check if USB is automatically powered off.