socat ioctl error while using "qm terminal ..."

[proxdrop]

I have a setup where qm terminal works just fine from the command line. I'd like to programmatically pass and retrieve data to this serial device. I thought a construct similar to this would work, but I get ioctl errors on it.

qm terminal <vmid> <<EOF
    show version
EOF

Error is:

DATE TIME socat[1391302] E tcgetattr(0, 0x63c03419c3c0): Inappropriate ioctl for device

Presumably socat is used here and it doesn't like how I'm passing commands. Manually entering "qm terminal <vmid>" works fine, as does the "show version" command. Is there a "known" way to do this, or otherwise pass and retrieve data to a VM's serial port?

 

[fiona]

Hi,
you could try to connect to the socket yourself if you need a different configuration than the interactive terminal uses with socat. The socket path is /var/run/qemu-server/<ID>.serial<N>

 

[proxdrop]

Thanks. Ultimately I moved on to other options instead. I just don't know enough about socat and ptys in general, though maybe I'll eventually revisit.

I did get a "working" solution by launching qm terminal <vmid> inside of a screen session, then using screen -X stuff <data> to pass along my commands. Very janky, barely functional, but it did work.

 

[proxdrop]

Ah, it was a bit easier than I expected. I had to install netcat-openbsd for support for Unix sockets, but a simple nc -U /var/run/qemu-server/<vmid>.socket works mostly fine. There's some shenanigans with closing the connection after the script completes, but otherwise it seems workable.

EDIT: cat <testscript> | nc -U /var/lib/qemu-server/<vmid>.socket# -w 1 works perfectly fine. Next test would be assigning the results to a variable or file, but I won't bother to update the thread for that. Thanks for the help.