[uml-user] UML hangs with con=fd:0,fd:1 if stdin is no tty
Hello, I'm trying to use UML to provide a "standard environment" for computational jobs in a Grid computing setting. So, I launch "linux mem=256M ubd0=apppot0.img con=null con0=fd:0,fd:1 root=/dev/ubda umid=my". The /etc/inittab within the UML machine is set up to run a certain non-interactive script instead of the regular multiuser boot. Everything runs fine if I start the UML in a terminal. However, if I redirect stdin from a non-tty stream (e.g., /dev/null), then all output disappears as soon as control is passed to userspace, and the CPU usage of the host machine goes up to 100%. These are the last lines printed to stdout: Initialized stdio console driver Console initialized on /dev/tty0 console [tty0] enabled Initializing software serial port version 1 console [mc-1] enabled ubda: unknown partition table registered taskstats version 1 Is there a way I can run a UML and have all its output redirected to a stream, and stdin connected to /dev/null ? This is how non-interactive jobs are run in a batch system, and it would be difficult to work around. I'm using the UML `linux` 2.6.35.1 from the Ubuntu 10.10 package `user-mode-linux` version 2.6.35-1um-0ubuntu1. The UML filesystem image contains a standard minimal Debian squeeze (except for the startup scripts). Thanks for any help! Riccardo -- WhatsUp Gold - Download Free Network Management Software The most intuitive, comprehensive, and cost-effective network management toolset available today. Delivers lowest initial acquisition cost and overall TCO of any competing solution. http://p.sf.net/sfu/whatsupgold-sd ___ User-mode-linux-user mailing list User-mode-linux-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-user
Re: [uml-user] UML hangs with con=fd:0,fd:1 if stdin is no tty
On Fri, Apr 29, 2011 at 5:14 PM, Riccardo Murri wrote: > Hello, > > I'm trying to use UML to provide a "standard environment" for > computational jobs in a Grid computing setting. > > So, I launch "linux mem=256M ubd0=apppot0.img con=null con0=fd:0,fd:1 > root=/dev/ubda umid=my". The /etc/inittab within the UML > machine is set up to run a certain non-interactive script instead of > the regular multiuser boot. Do you really need a full blown disk image with a inittab? I would use hostfs. E.g: ./linux rootfstype=hostfs init=/path/to/work/doit.sh con=null con0=fd:0,fd:1 &> uml.log < /dev/null BTW: When doit.sh is done UML panics with "Kernel panic - not syncing: Attempted to kill init!". This is okay. Anyway, what is the exact command-line which causes UML to hang? Can you provide me a stand alone test case? -- Thanks, //richard -- WhatsUp Gold - Download Free Network Management Software The most intuitive, comprehensive, and cost-effective network management toolset available today. Delivers lowest initial acquisition cost and overall TCO of any competing solution. http://p.sf.net/sfu/whatsupgold-sd ___ User-mode-linux-user mailing list User-mode-linux-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-user
Re: [uml-user] UML hangs with con=fd:0,fd:1 if stdin is no tty
Hi Richard, On Fri, Apr 29, 2011 at 5:47 PM, richard -rw- weinberger wrote: > Anyway, what is the exact command-line which causes UML to hang? > Can you provide me a stand alone test case? > Here it is: * download the 64-bit kernel: http://uml.devloop.org.uk/kernels/kernel64-2.6.35.7.bz2 * download the 64-bit filesystem http://fs.devloop.org.uk/filesystems/Debian-Squeeze/Debian-Squeeze-AMD64-root_fs.bz2 * Run (this works regularly): ./kernel64-2.6.35.7 umid=my mem=256M \ ubd0=Debian-Squeeze-AMD64-root_fs root=/dev/ubda \ con=fd:0,fd:1 * Now redirect stdin from /dev/null; the UML hangs and cannot be shutdown even from uml_mconsole (I have to manually kill the processes): ./kernel64-2.6.35.7 umid=my mem=256M \ ubd0=Debian-Squeeze-AMD64-root_fs root=/dev/ubda \ con=fd:0,fd:1 Do you really need a full blown disk image with a inittab? > I would use hostfs. > E.g: > ./linux rootfstype=hostfs init=/path/to/work/doit.sh con=null > con0=fd:0,fd:1 &> uml.log < /dev/null Well, the idea is that users get a "reference disk image", which they can run on their desktop to do development; when they are done with the coding and it runs on the reference machine, they can submit to the Grid. I guess we could do that with hostfs as well, but then we risk running into more permission problems than by distributing "opaque" disk images that users can boot like a regular VM. Thanks, Riccardo -- WhatsUp Gold - Download Free Network Management Software The most intuitive, comprehensive, and cost-effective network management toolset available today. Delivers lowest initial acquisition cost and overall TCO of any competing solution. http://p.sf.net/sfu/whatsupgold-sd ___ User-mode-linux-user mailing list User-mode-linux-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-user
Re: [uml-user] UML hangs with con=fd:0,fd:1 if stdin is no tty
On Fri, Apr 29, 2011 at 6:10 PM, Riccardo Murri wrote: > Hi Richard, > > On Fri, Apr 29, 2011 at 5:47 PM, richard -rw- weinberger > wrote: >> Anyway, what is the exact command-line which causes UML to hang? >> Can you provide me a stand alone test case? >> > > Here it is: > I fear you cannot use /dev/null (or any other non-tty file) as stdin. :-( UML uses poll() to detect whether input is available from stdin. As you can always read from /dev/null poll() doesn't block and UML gets flooded with interrupts. Do you really need stdin set to /dev/null? Can't you use a tool like screen to detach UML from your terminal? -- Thanks, //richard -- WhatsUp Gold - Download Free Network Management Software The most intuitive, comprehensive, and cost-effective network management toolset available today. Delivers lowest initial acquisition cost and overall TCO of any competing solution. http://p.sf.net/sfu/whatsupgold-sd ___ User-mode-linux-user mailing list User-mode-linux-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-user
Re: [uml-user] UML hangs with con=fd:0,fd:1 if stdin is no tty
On Fri, Apr 29, 2011 at 6:46 PM, richard -rw- weinberger wrote: > I fear you cannot use /dev/null (or any other non-tty file) as stdin. :-( > UML uses poll() to detect whether input is available from stdin. > As you can always read from /dev/null poll() doesn't block and > UML gets flooded with interrupts. > > Do you really need stdin set to /dev/null? > Can't you use a tool like screen to detach UML from your terminal? H... no :-( The purpose of this exercise is to launch a UML machine as a non-interactive job in a batch system, and this means it will run with stdin = /dev/null (or a file, which has the same `poll()` behavior). But I can still redirect stdin from a named FIFO and attach a "silent" process to it: mkfifo fake.stdin (sleep 365d > fake.stdin) & linux ... con=fd:0,fd:1 < fake.stdin This apparently works; I wonder whether there is a simpler/better solution. Thanks for your help! Riccardo -- WhatsUp Gold - Download Free Network Management Software The most intuitive, comprehensive, and cost-effective network management toolset available today. Delivers lowest initial acquisition cost and overall TCO of any competing solution. http://p.sf.net/sfu/whatsupgold-sd ___ User-mode-linux-user mailing list User-mode-linux-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-user
Re: [uml-user] UML hangs with con=fd:0,fd:1 if stdin is no tty
On Fri, Apr 29, 2011 at 7:05 PM, Riccardo Murri wrote: > But I can still redirect stdin from a named FIFO and attach a "silent" > process to it: Sure, but you'll still need a wrapper script which creates this FIFO in the grid node. I've had enough fun with sge, lsf, ... ;) -- Thanks, //richard -- WhatsUp Gold - Download Free Network Management Software The most intuitive, comprehensive, and cost-effective network management toolset available today. Delivers lowest initial acquisition cost and overall TCO of any competing solution. http://p.sf.net/sfu/whatsupgold-sd ___ User-mode-linux-user mailing list User-mode-linux-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-user
