I am trying to start my uml with:
./linux mem=256M ubd7=swap eth0=tuntap,,, con0=fd:0,fd:1 con=pts

Here is a kernel output:
Checking for the skas3 patch in the host...found
Checking for /proc/mm...found
Checking PROT_EXEC mmap in /tmp...OK
Kernel virtual memory size shrunk to 258998272 bytes
Linux version 2.6.9-skas3-v8-rc1-bs7 (td@mammoth) (gcc version 3.2.2) #1 Tue Jun 21 15:28:46 CDT 2005
Built 1 zonelists
Kernel command line: mem=256M ubd7=swap eth0=tuntap,,, con0=fd:0,fd:1 con=pts root=98:0
PID hash table entries: 2048 (order: 11, 32768 bytes)
Dentry cache hash table entries: 65536 (order: 6, 262144 bytes)
Inode-cache hash table entries: 32768 (order: 5, 131072 bytes)
Memory: 256512k available
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 syscall emulation patch for ptrace...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/td/.uml/VarQr4/mconsole
ubd: Synchronous mode
Netdevice 0 : TUN/TAP backend - IP =
VFS: Disk quotas dquot_6.5.1
Dquot-cache hash table entries: 1024 (order 0, 4096 bytes)
RAMDISK driver initialized: 16 RAM disks of 4096K size 1024 blocksize
NET: Registered protocol family 2
IP: routing cache hash table of 2048 buckets, 16Kbytes
TCP: Hash tables configured (established 16384 bind 32768)
ip_conntrack version 2.1 (2004 buckets, 16032 max) - 176 bytes per conntrack
ip_tables: (C) 2000-2002 Netfilter core team
NET: Registered protocol family 1
NET: Registered protocol family 17
Initializing software serial port version 1
Using anticipatory io scheduler
 ubda: unknown partition table
 ubdh: unknown partition table
Initializing stdio console driver
kjournald starting.  Commit interval 5 seconds
EXT3-fs: mounted filesystem with ordered data mode.
VFS: Mounted root (ext3 filesystem) readonly.
Warning: unable to open an initial console.

I have tried many tips from the list archives, including devfs=nomount/mount root=/dev/ubd/0.  Any other ideas?