[Netkit.users] Too many netkit machines?

Massimo Rimondini rimondin at dia.uniroma3.it
Fri Mar 18 14:29:58 CET 2011

Dear Gareth,

the issue you are reporting seems quite strange. There should be no hard
limit apart from computational resources. On the other hand, I could
only just start 45 virtual machines (with a "factory configuration") on
a Core 2 Quad with 4GB of RAM without any problems.

Here is a first checklist of things that come into my mind:
- disable exec-shield (|sysctl -w kernel.exec-shield=0);|
- check for messages from the host kernel; some actions (e.g.
out-of-memory killing) are undertaken without the user being notified;
- check how many running processes/threads you have (unlikely to happen,
but you might be running out of PIDs);
- check that you can launch multiple (by "multiple" I mean "really
many") instances of the terminal emulator you are using; a crashing
terminal emulator could be another cause for apparently inexplicable
virtual machine aborts.


On 03/16/2011 09:16 PM, Gareth Lapworth wrote:
> Dear All,
> I have just joined the list, so I do apologise if this has been asked
> before - I have also searched the website, and looked through the
> mailing list archives but I didn't seem to find an answer to my
> problem.
> I am in the process of building a netkit lab.  I have 37 of my
> machines currently running but it seems that I have hit a wall and I
> am unable to launch any more.  When I attempt to launch a further
> machine, an xterm executes and quickly dies.  I ran the command
> vstart vm --verbose --con0=this to see if I could catch the error
> message before it disappeared,  The following data was displayed:
> ============= Starting virtual machine "vm" =============
>    Kernel:     /opt/netkit/kernel/netkit-kernel
>    Modules:    /opt/netkit/kernel/modules
>    Memory:     32 MB
>    Model fs:   /opt/netkit/fs/netkit-fs
>    Filesystem: /home/glapworth/labs/ctec3427_cw2/nw-c/vm.disk (new)
>    Hostfs at:  /home/glapworth
> Running ==> /opt/netkit/kernel/netkit-kernel
> modules=/opt/netkit/kernel/modules name=vm title=vm umid=vm mem=36M
> ubd0=/home/glapworth/labs/ctec3427_cw2/nw-c/vm.disk,/opt/netkit/fs/netkit-fs
> root=98:1 uml_dir=/home/glapworth/.netkit/mconsole
> hosthome=/home/glapworth con0=fd:0,fd:1 con1=null SELINUX_INIT=0
> Locating the bottom of the address space ... 0x10000
> Locating the top of the address space ... 0xc0000000
> Core dump limits :
> 	soft - 0
> 	hard - NONE
> Checking that ptrace can change system call numbers...OK
> Checking syscall emulation patch for ptrace...OK
> Checking advanced syscall emulation patch for ptrace...OK
> Checking for tmpfs mount on /dev/shm...OK
> Checking PROT_EXEC mmap in /dev/shm/...OK
> Checking for the skas3 patch in the host:
>   - /proc/mm...not found: No such file or directory
>   - PTRACE_FAULTINFO...not found
>   - PTRACE_LDT...not found
> UML running in SKAS0 mode
> Adding 2617344 bytes to physical memory to account for exec-shield gap
> Terminated
> I can't see anything in this output that corresponds to a problem
> other than the word "Terminated". The machine I am running on is a
> quad core Xeon with 6Gb RAM running Ubuntu 10.04.  My system shows
> that I have only used 647Mb RAM at the moment and therefore I should
> have adequate to continue.  My CPU is happily running at 5% usage on
> average so this shouldn't be too taxing on the hardware.
> I've checked my file limits and I am not getting any too many open
> files errors.  Any ideas or help would be greatly appreciated.
> Thanks in advance.
> All the best,
> Gareth
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> Netkit.users a list.dia.uniroma3.it
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