Subject: Re: bug#40125: Problem with guix offload: Remote channel closed

From: Mikael Djurfeldt <[email-masked]>
Date: Sun, 22 Mar 2020 19:21:02 +0100

I did this.

What is a bit strange is that the error message seemingly randomly alters
between what I already reported above and the following:

mdj@hat:~/prusa$ guix offload test
guix offload: testing 1 build machines defined in
'/etc/guix/machines.scm'...
guix offload: Guix is usable on 'wand.pdc.kth.se' (test returned
"/gnu/store/883yjkl46dxw9mzykykmbs0yzwyxm17z-test")
guix offload: 'wand.pdc.kth.se' is running GNU Guile 3.0.1
sending 1 store item (0 MiB) to 'wand.pdc.kth.se'...
exporting path `/gnu/store/kw12ny565xl5p05ag6ysgshc9mhh4rz2-export-test'
guix offload: error: unknown error while sending files over SSH

This error message is more common. In this case, I couldn't see anything
obviously strange except the following backtrace which contains strange
characters:

31963 write(2, "Backtrace:\n          13 (apply-smob/1 #<catch-closure
56464c2232a0>)\nIn ice-9/boot-9.scm:\n    718:2 12 (call-with-prompt
(\"prompt\") #<procedure 56464c2407e0 \342\200\246> \342\200\246)\nIn
ice-9/eval.scm:\n    619:8 11 (_ #(#(#<directory (guile-user)
56464c2c4750>)))\nIn ice-9/command-line.scm:\n   181:18 10 (_ #<input:
string 56464c2d2bd0>)\nIn unknown file:\n           9 (eval (begin
(use-modules (guix) (srfi srfi-34) # #) \342\200\246) #)\nIn
ice-9/eval.scm:\n   721:20  8 (primitive-eval (begin (use-modules (guix)
(srfi \342\200\246) \342"..., 1150 <unfinished ...>

I have also noticed that the above (the error message) happens inside the
function send-files. It is the last error clause at the end of the function
which reports the error message.

I'd like to be able to, e.g., modify the function send-files to give some
debugging output. How can I easily do that? Should I checkout guix with git
and try to run it in the source tree? Or do you have other suggestions?

Best regards,
Mikael

On Sat, Mar 21, 2020 at 11:16 PM Ludovic Courtès <[email-masked]> wrote:

> Hi Mikael,
>
> Mikael Djurfeldt <[email-masked]> skribis:
>
> > I will look at the other buh reports. Meanwhile, do you have any hint on
> > where to look/insert logging code in order to see what is going on?
>
> On ‘wand’, can you run something like:
>
>   sudo strace -s 500 -p $(pidof sshd) -f -o sshd.log
>
> After that, run ‘guix offload test’ from the other host, and check what
> ‘sshd.log’ contains.  If would in particular look for all the ‘execve’
> syscalls as well as what happens right before ‘exit_group’ syscalls.
> There are probably error messages lurking there.  :-)
>
> You can share excerpts of the log but note that it will contain
> sensitive crypto material, so beware.
>
> Thanks in advance,
> Ludo’.
>