log commands and stdout/stderr

[rn]

I was debugging an issue with LCOW and it seems that gcs is shelling out to a number of commands inside the utility VM. It would be useful for debug if the code would log:

• the full command line of commands executed
• the stdout and stderr of the command

[jterry75]

@jhowardmsft - You said docker will show you these logs? How can @rn view them or am I missing that these are different commands than what you thought I had said offline.

Otherwise will use an io.MultiWriter here

[lowenna]

Certainly the command being executed itslogged in full when the daemon is run in debug mode (dockerd -D)

eg (just a couple)

DEBU[2017-08-07T13:21:47.207258300-07:00] opengcs: RunProcess: ls /sys/bus/scsi/devices/0:0:0:3/block

DEBU[2017-08-07T13:21:47.236063500-07:00] opengcs: RunProcess: mkfs.ext4 -q -E lazy_itable_init=1 -O ^has_journal,sparse_super2,uninit_bg,^resize_inode /dev/sdb

[rn]

I may have missed that in the busy debug logs. Do you know if the output of the commands is also avail?

[lowenna]

@rn no, it's not. What commands specifically are you interested in?

[rn]

just in general. It's hard to predict which command may fail :)

It would have helped debugging in the past if I had gotten the error messages, Most/all of the commands are very quiet so it shouldn't log much.

[lowenna]

I think failures do log the output. Maybe they didn't in earlier incantations of the code. True, most are quiet, but it should be obvious from the logs if a command does fail. I'm concerned about universally adding it though (success cases). Esp for tar2vhd/vhd2tar.

[rn]

OK. I don't recall if I saw something in the daemon logs or not. Let me close this for now as the commands themselves are logged and if I hit an issue again I may re-open with additional info.