[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Question: Redirect guest kernel's message via serial port to a file on dom0
On Tue, 2015-09-01 at 11:15 -0400, Meng Xu wrote: > 2015-09-01 6:52 GMT-04:00 Ian Campbell <ian.campbell@xxxxxxxxxx>: > > On Tue, 2015-08-25 at 09:04 -0400, Meng Xu wrote: > > > 2015-08-25 3:42 GMT-04:00 Andrew Cooper <andrew.cooper3@xxxxxxxxxx>: > > > > On 25/08/2015 03:48, Meng Xu wrote: > > > > > Hi Andrew, > > > > > > > > > > Thank you so much for your suggestion! I tried but have some > > > > > questions. > > > > > > > > > > 2015-08-24 4:10 GMT-04:00 Andrew Cooper < > > > > > andrew.cooper3@xxxxxxxxxx>: > > > > > > On 24/08/2015 04:01, Meng Xu wrote: > > > > > > > > > > > > Hi, > > > > > > > > > > > > I'm trying to use a PV guest VM on Xen to help debug Linux. > > > > > > I was using VirtualBox to help debug Linux kernel by > > > > > > redirecting > > > > > > the output of the serial port of the VM to a file in the host. > > > > > > I > > > > > > can do it in VirtualBox. > > > > > > > > > > > > [Why do I want to achieve this?] > > > > > > It is much faster to reboot a VM than rebooting the physical > > > > > > machine. > > > > > > I don't need another machine to physically connect to the > > > > > > serial > > > > > > port of the development machine. > > > > > > I want to use Xen for as many things as possible. ;-) > > > > > > > > > > > > I tried to google a tutorial or manual about how to configure > > > > > > it, > > > > > > but didn't find any. :-( > > > > > > > > > > > > In my understanding, I need to do the following things: > > > > > > 1) I need to add a line (something like "serial=") in the > > > > > > guest's > > > > > > configuration file to specify the serial port device to the VM; > > > > > > 2) I need some configuration to redirect the output of the > > > > > > serial > > > > > > device to a file in domU; > > > > > > 3) After that, I can configure the kernel command line in the > > > > > > VM to > > > > > > dump the kernel message via the serial port of the VM. (I know > > > > > > how > > > > > > to do this step.) > > > > > > > > > > > > Did anyone have tried this before and have some configuration I > > > > > > can > > > > > > refer to? or > > > > > > Could anyone give me some references that describes how to > > > > > > configure the above three steps? > > > > > > > > > > > > I really appreciate any help or suggestion or comment. > > > > > > > > > > > > > > > > > > Configure xenconsoled to log guest consoles to file "- > > > > > > -log=guest" > > > > > > at which point anything sent to hvc0 will be logged to files in > > > > > > /var/log/xen/guest/console (configurable with "--log-dir=") > > > > > > > > > > I set "XENCONSOLED_TRACE=guest" under /etc/default/xencommons , > > > > > because in /etc/init.d/xencommons, it has: test -z > > > > > "$XENCONSOLED_TRACE" || XENCONSOLED_ARGS=" - > > > > > -log=$XENCONSOLED_TRACE" > > > > > > > > > > So I think this is what you mean by "--log=guest"; After I set > > > > > this > > > > > variable and restart the xencommons by "service xencommons > > > > > restart" > > > > > on > > > > > dom0 (Ubuntu 12.04LTS), I still couldn't find the file in > > > > > /var/log/xen/guest/console when I reboot the VM. > > > > > Actually, "find /var -name console" returns no result. > > > > > > > > > > **My question is:** > > > > > Is there anything else I need to configure to get the > > > > > /var/log/xen/guest/console? > > > > > > > > > > I don't see the folder under /var/log/xen. :-( > > > > > > > > You probably need to mkdir it then, or extend the args list with > > > > --log-dir=/var/log/xen > > > > > > I tried both, but neither of them works. :-( > > > > > > I'm wondering if anyone has some document about how to do this? > > > If there is some document about how to debug this configuration > > > issue, > > > it could also be helpful... > > > But I didn't find it after googling and trying for 2 hours...:-( > > > > > > Below is the detail of what I tried: > > > > > > I tried to mkdir /var/log/xen/guest > > > > The correct (default) path is /var/log/xen/console I think. > > > > > and restart the xencommons by > > > "service xencommons restart", > > > > Are you using sysvinit or systemd? > > I'm using sysvinit, since "pidof /sbin/init " shows that init process > has pid = 1. What if systemd were /sbin/init? > > If the latter are you using the systemd > > units of the sysvinit scripts via systemd's LSB compat mode? > > > > If you are using the systemd units then I think they might be > > configured > > elsewhere. > > Do I have to explicitly configure a virtual serial device to the PV > VM, in order to make Xen create the /var/log/xen/console file? > > Right now, when I ssh into the PV VM and issue the command #echo 1 > > /dev/ttyS0, it returns error "echo: write error: Input/output error". > I'm guessing maybe it's because the VM has no serial port configured? > > Thank you very much for your time and help in this issue! Are we talking about HVM guests or PV guests here? I had assumed PV... A PV guest doesn't have /dev/ttyS0, it has no serial devices. Such guests have /dev/hvc0 as their console. An HVM guest needs to be told where the serial device (ttyS0) goes via the guest config, serial = 'pty' is the magic rune to cause it to be logged by xenconsoled. There are other possibilities, check xl.cfg(5). Ian. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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