Blaisorblade and Sarah,
Thank you for your assistance. It turned out that I did not have
CONFIG_BLK_DEV_UBD_SYNC=y
defined. After rebuilding the kernel, building a new root_fs, and a
days worth of tweaking, it finally started working.

The only problem I have left is that with the command line
./vmlinux ubd0=rootfs.ext3 ubd1=swap con0=fd:0,fd:1 con=pts
the host system reports hundreds of processes like;
./vmlinux [/sbin/udevstart]
./vmlinux [/bin/bash]
./vmlinux [/bin/sh]
./vmlinux [initlog]
and others. Probably something in the root_fs init scripts.
I'll find out today if it's usable.

Thanks again.


Blaisorblade wrote:

On Wednesday 16 February 2005 19:33, Greg Huber wrote:


Hello,
I'm having what I hope is a simple problem getting a UML client to run.

My host system is Fedora Core 3, up to date, running
kernel-2.6.10-1.760_FC3 (unmodified).
I read that kernel's 2.6.9 and later should be good to go.
I created the 'udb' device nodes, although I'm not sure the host needs
them.


The host does not need them.


I also compilied and loaded the uml_utilities on this system.

Right.


For the guest, I used the 2.6.9 kernel from www.kernel.org and compilied
as described in the UserModeLinux-HOWTO and some other articles from
the web. I believe I have turned on everything needed, and just about
everything available. The kernel image and modules all compilied without
incident.

For the root filesystem I pulled down the closest image I could find,
root_fs.fc-2-client.pristine.20040504. I then mounted it and loaded
the modules from the kernel build. I also created the 'ubd' device
nodes, although they appear to be created automatically.

All appreared to go well but when I start vmlinux, I get the
following...

[umluser uml]$ ./vmlinux ubd0=root_fs.fc-2-client.pristine.20040504
Checking for the skas3 patch in the host...not found
Checking for /proc/mm...not found
tracing thread pid = 12878
Linux version 2.6.9uml ([EMAIL PROTECTED]) (gcc version 3.4.2 20041017 (Red
Hat
3.4.2-6.fc3)) #6 Tue Feb 15 13:20:33 EST 2005
Built 1 zonelists
Kernel command line: ubd0=root_fs.fc-2-client.pristine.20040504
root=98:0
PID hash table entries: 256 (order: 8, 4096 bytes)
Dentry cache hash table entries: 8192 (order: 3, 32768 bytes)
Inode-cache hash table entries: 4096 (order: 2, 16384 bytes)
Memory: 28888k available
Security Scaffold v1.0.0 initialized
Capability LSM initialized
Mount-cache hash table entries: 512 (order: 0, 4096 bytes)
Checking for host processor cmov support...Yes
Checking for host processor xmm support...No
Checking that ptrace can change system call numbers...OK
Checking that host ptys support output SIGIO...Yes
Checking that host ptys support SIGIO on close...No, enabling workaround
Checking for /dev/anon on the host...Not available (open failed with
errno 2)
NET: Registered protocol family 16
mconsole (version 2) initialized on /home/uml/.uml/ao52lJ/mconsole
audit: initializing netlink socket (disabled)
audit(0.4294966929:0): initialized
VFS: Disk quotas dquot_6.5.1
Dquot-cache hash table entries: 1024 (order 0, 4096 bytes)
devfs: 2004-01-31 Richard Gooch ([EMAIL PROTECTED])
devfs: boot_options: 0x0
Initializing Cryptographic API
RAMDISK driver initialized: 16 RAM disks of 16384K size 1024 blocksize
md: md driver 0.90.0 MAX_MD_DEVS=256, MD_SB_DISKS=27
NET: Registered protocol family 2
IP: routing cache hash table of 128 buckets, 4Kbytes
TCP: Hash tables configured (established 2048 bind 585)
Initializing IPsec netlink socket
NET: Registered protocol family 1
NET: Registered protocol family 17
Initializing software serial port version 1
Initializing stdio console driver
md: Autodetecting RAID arrays.
md: autorun ...
md: ... autorun DONE.
VFS: Cannot open root device "98:0" or unknown-block(98,0)
Please append a correct "root=" boot option
Kernel panic - not syncing: VFS: Unable to mount root fs on
unknown-block(98,0)





First question is why can't it find 'root'??


Seems like ubd support was not compiled in the guest kernel (with the .config it can be easily verified). Try enabling the option and retrying.


Is this a LVM issue??

No.


Second question is the root filesystem I pulled down contained a kernel
image
and modules,


They aren't needed there, they are there because it was probably a i386 install originally. That's just a guess however.

You have, instead, to install the modules you build inside the root filesystem.


Is this required. If so does this mean that you have to compile
a kernel twice, once with ARCH=um and once without??


Not at all.


Any insight you can provide would be greatly appreciated.








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