Re: [Xen-users] Xen questions - Swap, networking and errors

[Daniel Lang <dlang@xxxxxxxxxx>]

M.A. Williamson wrote:
>> This is my first time trying Xen.  I have installed Xen-2.0.6, on a
>> Debian Sarge server.  I have a few questions that I haven't been able to
>> find answers to in the documentation or FAQs.
> 
> 
> OK, welcome to the community! I'll try and answer your questions. If
> there's anything you feel should be in a FAQ, feel free to get a Wiki
> account and add it at http://wiki.xensource.com.
> 
>> 1)When I boot xen0, the specified amount of RAM shows up in top
>> correctly, but the swap partitions I have are not activated.  When I
>> attempt to activate swap myself, I recieve the following error message:
>>     xen:/# swapon /dev/hde2
>>     swapon: /dev/hde2: No such device or address
>> The server has a mirrored RAID1 setup, and both MD devices are detected
>> and mounted properly.  However, I am confused about why the kernel does
>> not see the hard disk partitions themselves.  The disks are SATA drives,
>> and so at first I thought perhaps it didn't recongize the drives, but if
>> that were the case, I don't think either MD device would be detected
>> properly.  Is there a boot option that I have not seen to address this
> 
> 
> Are all the drives in the machine the same? Are other partitions on hde
> in the RAID configuration.
> 
> If the drives are on different controllers (e.g. a couple of PATA and a
> SATA, as on some systems) then the default kernel config may not be
> building the drivers for hde but still builds enough drivers for the MD
> devices to work.
> 
>> As a side note, what is a proper amount of RAM needed for xen0?  I have
>> not found any documentation really stating how much RAM is need for the
>> priveledged Xen instance.  The server itself has 4GB of RAM.  Should
>> xen0 have all 4GB of RAM to partition to the xenU domains?
> 
> 

I went back and checked /proc/partitions.  Under a normal kernel, all of
the partitions show up as /dev/hde* and /dev/hdg*, but with the Xen
kernel, all of the partitions are /dev/sda* and /dev/sdb*  Now that I've
found the correct device names, swap is turned on.

> RAM that you give to dom0 can't be allocated to domUs. 256MB should
> probably be enough for a slim dom0. If you use LVM snapshots that'll
> need to be larger though.
> 
> You can use the "balloon driver" to reduce the size of dom0 after
> booting if you need more memory for other domains.
> 
>> 2)With the default xend config, when I start xend the bridge device
>> xen-br0 is created.  However, after that I lose all network activity to
>> xen0.  I noticed that no vif devices were created, only xen-br0.
>> Initially, xen-br0 doesn't have an IP.  I've tried setting it to the IP
>> of eth0, and a 192.168.0.x IP, but I still cannot get networking up.
> 
> 
> Sounds a bit broken... What should happen is that eth0's IP is
> transferred to xen-br0.
> 
> Do you have any existing bridge setup? Anything else unusual in your
> networking config?

This is a brand new server meant to run Xen.  It has an Intel gigabit
NIC, but only one.  I was using the default configuration from a source
install of Xen-2.0.6.   There are/were not any other bridge devices
working.  The thing that stood out to me was that no vif devices were
created, which from the documentation I've found, seems unusual.

> 
>> I changed the xend config to use the network-route rather than network,
>> and when I start xend, networking doesn't go down, but xen-br0 is not
>> created.  I am not sure why the default network config is not working.
>> Do I need to make changes to the routing tables?
> 
> 
> You won't get a xen-br0 if you're using the routed config - you don't
> need it. Don't know about the routing tables as I've never used the
> routed config myself.
> 
> <snip>
> 
>> ioctl: LOOP_SET_FD: Device or resource busy
> 
> <snip>
> 
>> vif-route up vif=vif1.0 domain=TestDomain mac=aa:00:00:62:e9:12
> 
> 
>> I am not sure why the error message LOOP_SET_FD: Device or resource busy
>> appears, since the loopback device I created the root filesystem on is
>> not mounted or being used.
> 
> 
> What does ls -l /dev/loop* give you?

xen:~# ls -l /dev/loop*
brw-rw----  1 root disk 7, 0 Jun 29 16:32 /dev/loop0
brw-rw----  1 root disk 7, 1 Jun 29 16:32 /dev/loop1
brw-rw----  1 root disk 7, 2 Jun 29 16:32 /dev/loop2
brw-rw----  1 root disk 7, 3 Jun 29 16:32 /dev/loop3
brw-rw----  1 root disk 7, 4 Jun 29 16:32 /dev/loop4
brw-rw----  1 root disk 7, 5 Jun 29 16:32 /dev/loop5
brw-rw----  1 root disk 7, 6 Jun 29 16:32 /dev/loop6
brw-rw----  1 root disk 7, 7 Jun 29 16:32 /dev/loop7

Thanks for the help so far.  One problem taken care of.  Are there
developer docs that might help explain the reason for the xenU instance
crashing?

Regards,

Dan Lang

-- 
Daniel Lang

Systems Administrator
SevenL Networks
416.642.1235
1.866.639.5123

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users