Tag Archives: systemd

Mount encfs folder on startup with systemd

A quick note on how to encrypt a folder with encfs and then mount it on boot via a systemd startup script. In my case the folder is located on a network drive and I wanted it to happen whether I was logged in or not.

Create encfs folder:

encfs <path to encrypted folder> <path to mount decrypted folder>

Follow the prompts to create the folder and set a password.

Next create a file which will contain your decryption password

echo "YOUR_PASSWORD" > /home/user/super_secret_password_location
chmod 700 /home/user/super_secret_password_location

Create a simple script to be called by systemd on startup using cat to pass your password over to encfs

cat super_secret_password_location | encfs -S path_to_encrypted_folder path_to_mount_decrypted_folder

Finally create a systemd unit to run your script on startup:

vim /etc/systemd/system/mount-encrypted.service
Description=Mount encrypted folder 

ExecStartPre=/bin/sleep 20 


Then enable the unit:

sudo systemctl daemon-reload
sudo systemctl enable mountt-encrypted.service

VGA Passthrough with Threadripper

An unfortunate bug exists for the AMD Threadripper family of GPUs which causes VGA Passthrough not to work properly. Fortunately some very clever people have implemented a workaround to allow proper VGA passthrough until a proper Linux Kernel patch can be accepted and implemented. See here for the whole story.

Right now my Thrdearipper 1950x successfully has GPU passthrough thanks to HyenaCheeseHeads “java hack” applet.  I went this route because I really didn’t want to try and recompile my ProxMox kernel to get passthrough to work. Per the description “It is a small program that runs as any user with read/write access to sysfs (this small guide assumes “root”). The program monitors any PCIe device that is connected to VFIO-PCI when the program starts, if the device disconnects due to the issues described in this post then the program tries to re-connect the device by rewriting the bridge configuration.” Instructions taken from the above Reddit post.

  • Go to https://pastebin.com/iYg3Dngs and hit “Download” (the MD5 sum is supposed to be 91914b021b890d778f4055bcc5f41002)
  • Rename the downloaded file to “ZenBridgeBaconRecovery.java” and put it in a new folder somewhere
  • Go to the folder in a terminal and type “javac ZenBridgeBaconRecovery.java”, this should take a short while and then complete with no errors. You may need to install the Java 8 JDK to get the javac command (use your distribution’s software manager)
  • In the same folder type “sudo java ZenBridgeBaconRecovery”
  • Make sure that the PCIe device that you intend to passthru is listed as monitored with a bridge
  • Now start your VM

In my case (Debian Stretch, ProxMox) I needed to install openjdk-8-jdk-headless

sudo apt install openjdk-8-jdk-headless
javac ZenBridgeBaconRecovery.java

Next I have a little script on startup to spawn this as root in a detached tmux session, so I don’t have to remember to run it (If you try to start your VM before running this, it will hose passthrough on your system until you reboot it.) Be sure to change the script to point to wherever you compiled ZenBridgeBaconRecovery

cd /home/nicholas  #change me to suit your needs
sudo java ZenBridgeBaconRecovery

And here is the command I use to run on startup:

tmux new -d '/home/nicholas/passthrough.sh'

Again, be sure to modify the above to point to the path of wherever you saved the above script.

So far this works pretty well for me. I hate having to run a java process as sudo, but it’s better than recompiling my kernel.

Update 6/27/2018:  I’ve created a systemd service script for the ZenBaconRecovery file to run at boot. Here is my file, placed in
/etc/systemd/system/zenbridge.service:  (change your working directory to match the zenbridgebaconrecovery java file location. Don’t forget to do systemctl daemon-reload.)

Description=Zen Bridge Bacon Recovery 

ExecStart=/usr/bin/java ZenBridgeBaconRecovery 
Restart=on-failure # or always, on-abort, etc 


Update 8/18/2018 Finally solved for everyone!

Per an update on the reddit thread motherboard manufactures have finally put out BIOS updates that resolve the PCI passthrough problems. I updated my X399 Tachi to the latest version of its UEFI BIOS (3.20) and indeed PCI passthrough worked without any more wonky workarounds!

XAPI won’t start in Xenserver 7

I came home yesterday to discover that every last one of my VMs were unresponsive. It was most distressing. I couldn’t even SSH into my xenserver – it was unresponsive too. Its physical console had dropped into an emergency shell. A reboot allowed me to get a physical console again, but my networking and VMs would not start.

In trying to pick up the pieces and put everything back together I ran

systemctl --failed

which revealed several key services not running – namely openvswitch and xapi (very important services.) Manually starting them did nothing – they would silently fail and immediately quit working.

After banging my head against a wall for a bit (I really didn’t want to restore from backup) I stumbled across this post. It states in essence that xapi won’t start if the disk is full. I checked disk usage and it said I had a few gigs free, but thought I’d try the steps in the post anyway.

ls /var/log

revealed quite a lot of log files. I then decided to just delete all the .gz archived logs:

rm /var/log/*.gz

After doing this, xapi started. I restarted the hypervisor for good measure and everything came up – all back to normal as if nothing had happened.

It’s incredibly frustrating that Xenserver is designed to be a ticking time bomb with default configuration. If you don’t take care to manually delete old logs, or alternatively send logs to a remote log server, it will crash and burn. This is stupid. That being said, I was impressed that it recovered so gracefully once I freed up some disk space.

If you’re running xenserver, make sure you’re logging somewhere else – or put a cron job to delete old log files!