Re: [Qemu-devel] [questions] about qemu log

[Zhang Haoyu]

>>>> Hi, all
>>>>
>>>> If I use qemu command directly to run vm, bypass libvirt, how to configure 
>>>> qemu to assure that each vm has its own log file, like vmname.log?
>>>> For example, VM: rhel7-net has its own log file, rhel7-net.log,
>>>> VM:rhel7-stor has its own log file, rhel7-stor.log.
>>>
>>> -D /path/to/unique/file/name.log
>>>
>> -D option is to configure qemu_logfile for the output logs which are 
>> controlled by qmp command "logfile", which can be enabled/disabled on run 
>> time.
>> 
>> I want to configure the log file for the output of fprintf(stderr, fmt, 
>> ...), .etc,
>> i.e., how to redirect the output of fprintf(stderr, fmt, ...), or some other 
>> log-interface to a specified file?
>
>In a shell you would write something like:
>
>2> stderr.log
>
>You may also want to toggle QEMU's -msg timestamp=on option.
>
I think the "-msg -msg timestamp=on" option will add timestamp to the output of 
error_report(fmt, ...),
but where is the output? Which file saves the output?
And where is the output of fprintf(stderr, fmt, ...)?
Should I redirect of stderr to specified log file?

In libvirt code, when start a vm(qemuProcessStart), it will create a qemu log 
file named /var/log/libvirt/qemu/vmname.log,
and redirect the stderr and stdout to file descriptor of this qemu log file.

But if I run a vm directly by qemu command, bypass libvirt, then how to 
configure qemu to assure that each vm has its own log file,
and how to redirect the stderr, stdout to each vm's own log file?

Thanks,
Zhang Haoyu

>Cheers,
>Andreas