Re: [uml-user] Problem finding root file system

[Greg H. <gh...@va...>]

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 (uml@umluser) (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 (rg...@at...)
>>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.
>>    
>>
>
>  
>