| kiorky | hi; im trying to debug upstart inside a docker, and i would like to attach a gdb to it, but as it crashes directly, i cant | 10:50 |
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| kiorky | (idea is to launch one docker with the compiled init and attach a gdb from another shell) | 10:51 |
| kiorky | if someone has an idea on how i can debug ... | 10:51 |
| jodh | Kiorky: I've never used docker. Do you get any crash output? You could boot your docker environment specifying bash as your init, then start upstart in a separate pid namespace running with --no-startup-event, then attach gdb to that pid. | 12:03 |
| kiorky | jodh: well the difficulty is the docker magic between | 12:04 |
| kiorky | jodh: and that upstart wants pid - 1 | 12:04 |
| kiorky | jodh: well, i want to debug the start process, that's the real problem amongst all | 12:05 |
| jodh | kiorky: in all likelihood, the crash is probably due to some environment issue: try installing procenv into the docker environment (its in the debian and ubuntu archives, or https://launchpad.net/procenv/), and boot the docker container so that procenv runs first, logs the environment output, then execs upstart. I've blogged about how to do this for lxc here: | 12:05 |
| jodh | http://ifdeflinux.blogspot.co.uk/2013/04/observing-initial-lxc-environment-using.html | 12:05 |
| kiorky | jodh: i dont know why but init dies, without logs, so my idea was to gdb it | 12:05 |
| kiorky | jodh: lookin' thx | 12:06 |
| jodh | kiorky: yes, you can run upstart in the docker environment as *pid 1* if you put it into a new pid namespace within your docker environment. | 12:06 |
| kiorky | jodh: ha i see! | 12:06 |
| jodh | kiorky: are you sure there is no stdout/stderr output being logged by docker somewhere? no docker option to record the console? | 12:06 |
| kiorky | jodh: normally, all goes to docker logs, but anything is captured | 12:07 |
| kiorky | jodh: i have some logs, but nothing fatal | 12:07 |
| kiorky | just that the docker boot and after a little while, dies | 12:07 |
| kiorky | without explanation | 12:07 |
| kiorky | but i will look your blog post and go forward into trying to exec init inside a new pid namespace | 12:08 |
| jodh | kiorky: I've covered the technique in the cookbook too: http://upstart.ubuntu.com/cookbook/#debugging-another-instance-of-upstart-running-as-root-with-pid-1 | 12:09 |
| kiorky | jodh: in your setup, init starts and then you attach with gdb isnt it ? | 12:10 |
| kiorky | jodh: problem there is that init dies before i can even attach to it | 12:11 |
| kiorky | jodh: i mean on the cookbook | 12:11 |
| jodh | kiorky: Well, in the lxc example yes, but not in the first example using my clone utility. | 12:12 |
| jodh | kiorky: I still think it might be quicker to use the procenv trick to get a dump of the docker environment, then run procenv in a "normal" environment and diff the files. | 12:14 |
| kiorky | jodh: the clone is same, you one already running, isnt it ? | 12:16 |
| kiorky | :) | 12:16 |
| modafinil | I'm really at my wits-end here -- how can I, in an unprivileged upstart job, emit an event to start another job? | 13:58 |
| modafinil | I have a job to make logs for a service, so I want the service to start this job 'make sure my logs dir is owned by serviceuser' and then run itself unprivileged (using setgid/setuid) | 13:59 |
| modafinil | Really annoying that pre-start runs as the setuid user :/ | 14:00 |
| modafinil | obviusly sudo doesn't work | 14:00 |
| jodh | modafinil: easy - turn it round: have the job that handles your logs run as root, then make the job that actually runs the service (with setuid/setgid), specify 'start on stopped <log_job>'. | 14:13 |
| modafinil | jodh: the problem is that i have a bunch of jobs, and i want them all to use this one job (and set the variable of where the logs dir is) | 14:13 |
| modafinil | i think i figured it out though | 14:13 |
| modafinil | i can 'start on starting acmeco-*' to wildcard match in the log creation job | 14:14 |
| jodh | modafinil: have the root job that starts first 'export logdir' so that "$logdir" is available to all the non-priv jobs. | 14:16 |
| modafinil | jodh: i agree that would work, but its not really workable for this specific situation -- theres hundreds of different services and i don't want to have one thing that needs to know about them all | 14:20 |
| modafinil | this wildcard match definitely works though | 14:20 |
| modafinil | i appreciate your help! thanks! | 14:21 |
| kiorky | jodh: simpler solution; add a sleep(3) and recompile upstart ;) so i have the time to attach gdb with lxc-execute | 15:51 |
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