How to make Systemd service file run echo commands that contains special characters?

Question

I am trying to write a service file that unbinds a PCI device like this, after I run systemctl stop servicefile-name:

    ExecStop=/bin/echo 1 > "/sys/bus/pci/devices/0000\:03\:00.0/remove"

However the unbinding never occurs and the device is still active and running. Executing the echo command from the bash command line has no problems and removes the device just fine: echo 1 > /sys/bus/pci/devices/0000:03:00.0/remove

Running systemctl status servicefile-name shows that the echo command ran without any errors: (code=exited, status=0/SUCCESS). I am clearly not using the correct echo command syntax within the service file. I also tried to remove the escape characters but it still did not work

ExecStop=/bin/echo 1 > "/sys/bus/pci/devices/0000:03:00.0/remove"

Does anyone know how to remove/unbind devices at runtime from a systemd service file, give the special characters ":"?

Answer 1

ExecStop=... does not run bash. Therefore operators like > or & are not interpreted in the same way that bash would interpret them. systemd will simply run /bin/echo and pass 1, >, and "sys-bus-pci-devices-0000:03:00.0-remove" as arguments.

If you want > to act as bash redirection, then you need to pass this statement to the bash interpreter using bash -c.

Try this:

ExecStop=/bin/bash -c "/bin/echo 1 > /sys/bus/pci/devices/0000\:03\:00.0/remove"

I'm not as familiar with the escaping suggested by GAD3R, but you might also try that escaped string as well.

Answer 2

Use systemd-escape.

$ systemd-escape --path "/sys/bus/pci/devices/0000:03:00.0/remove"
sys-bus-pci-devices-0000:03:00.0-remove

Then edit your unit file:

ExecStop=/bin/echo 1 > "sys-bus-pci-devices-0000:03:00.0-remove"

see man systemd-escape