subjam - User Mode Linux in Debian Etch

User Mode Linux in Debian Etch

Saturday, 4. November 2006, 20:14:25

UML Configuration

Prepartion

1. Install user-mode-linux and related packages in debian
2. Get some filesystem images from Nagafix.co.uk UML Resources

Launch Two UML Instances

linux mem=128M ubda=cow1,/home/work/uml/Ubuntu-x86-root_fs umid=ubuntu1
linux mem=128M ubda=cow2,/home/work/uml/Ubuntu-x86-root_fs umid=ubuntu2

host# uml_mconsole ubuntu1 config eth0=mcast
host# uml_mconsole ubuntu2 config eth0=mcast
ubuntu1# ifconfig eth0 192.168.0.1 up
ubuntu2# ifconfig eth0 192.168.0.2 up

We can verify that we have connectivity by pinging one from the other.

TUN/TAP with Routing
Note: Tap devices are point-to-point connections. There can only be one UML using one at a time.

host# su root

Run the following bash script in host
chmod 666 /dev/net/tun
tunctl -u bob -t uml
ifconfig uml 192.168.1.1 up
iptables --flush
iptables --table nat --flush
iptables --delete-chain
iptables --table nat --delete-chain
iptables --table nat --append POSTROUTING --out-interface eth0 \
         -j MASQUERADE
iptables --append FORWARD --in-interface uml -j ACCEPT
echo 1 > /proc/sys/net/ipv4/ip_forward
echo 1 > /proc/sys/net/ipv4/conf/uml/proxy_arp
arp -Ds 192.168.1.2 eth0 pub 
route add -host 192.168.1.2 dev uml

host# exit
host# uml_mconsole ubuntu1 config eth0=tuntap,uml

ubuntu1# ifconfig eth0 192.168.1.2 up
ubuntu1# route add default gw 192.168.1.1
Configure /etc/resolv.conf in ubuntu1.

Compile From Source

Download Kernel Source

host# wget http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.18.tar.bz2
host# bunzip2 linux-2.6.18.tar.bz2 
host# tar xf linux-2.6.18.tar 
host# cd linux-2.6.18

Apply this patch from Jeff Dike

Index: linux-2.6.17/arch/um/os-Linux/process.c
===================================================================
--- linux-2.6.17.orig/arch/um/os-Linux/process.c 2006-09-20 11:15:08.000000000 -0400
+++ linux-2.6.17/arch/um/os-Linux/process.c 2006-09-20 13:35:24.000000000 -0400
@@ -140,11 +140,9 @@ void os_usr1_process(int pid)
* syscalls, and also breaks with clone(), which does not unshare the TLS.
*/

-inline _syscall0(pid_t, getpid)
-
int os_getpid(void)
{
- return(getpid());
+ return syscall(__NR_getpid);
}

int os_getpgrp(void)
Index: linux-2.6.17/arch/um/os-Linux/sys-i386/tls.c
===================================================================
--- linux-2.6.17.orig/arch/um/os-Linux/sys-i386/tls.c 2006-06-18 13:49:35.000000000 -0400
+++ linux-2.6.17/arch/um/os-Linux/sys-i386/tls.c 2006-09-20 13:37:27.000000000 -0400
@@ -3,8 +3,6 @@
#include "sysdep/tls.h"
#include "user_util.h"

-static _syscall1(int, get_thread_area, user_desc_t *, u_info);
-
/* Checks whether host supports TLS, and sets *tls_min according to the value
* valid on the host.
* i386 host have it == 6; x86_64 host have it == 12, for i386 emulation. */
@@ -17,7 +15,7 @@ void check_host_supports_tls(int *suppor
user_desc_t info;
info.entry_number = val[i];

- if (get_thread_area(&info) == 0) {
+ if(syscall(__NR_get_thread_area, &info) == 0){
*tls_min = val[i];
*supports_tls = 1;
return;
Index: linux-2.6.17/arch/um/os-Linux/tls.c
===================================================================
--- linux-2.6.17.orig/arch/um/os-Linux/tls.c 2006-08-15 21:59:56.000000000 -0400
+++ linux-2.6.17/arch/um/os-Linux/tls.c 2006-09-20 13:37:14.000000000 -0400
@@ -48,14 +48,11 @@ int os_get_thread_area(user_desc_t *info
#ifdef UML_CONFIG_MODE_TT
#include "linux/unistd.h"

-static _syscall1(int, get_thread_area, user_desc_t *, u_info);
-static _syscall1(int, set_thread_area, user_desc_t *, u_info);
-
int do_set_thread_area_tt(user_desc_t *info)
{
int ret;

- ret = set_thread_area(info);
+ ret = syscall(__NR_set_thread_area, info);
if (ret < 0) {
ret = -errno;
}
@@ -66,7 +63,7 @@ int do_get_thread_area_tt(user_desc_t *i
{
int ret;

- ret = get_thread_area(info);
+ ret = syscall(__NR_get_thread_area, info);
if (ret < 0) {
ret = -errno;
}

Apply this patch from Emmanuel Fleury

--- arch/um/include/sysdep-i386/stub.h.orig 2006-11-04
02:33:58.000000000 +0100
+++ arch/um/include/sysdep-i386/stub.h      2006-11-14
11:23:20.000000000 +0100
@@ -12,6 +12,7 @@
 #include "stub-data.h"
 #include "kern_constants.h"
 #include "uml-config.h"
+#include "asm/page.h"

Compile kernel and modules

host# make mrproper
host# make mrproper ARCH=um
host# make defconfig ARCH=um
host# make xconfig ARCH=um

CONFIGURE 2G/2G Host Address Space Split
CONFIGURE Host Filesystem
 
host# make ARCH=um

Run UML instance with the compiled "linux"
Configure networking

host# make modules_install INSTALL_MOD_PATH=/home/work/uml/mods/ ARCH=um
ubutu# mkdir -p /lib/modules/`uname -r`
ubutu# passwd
ubutu# apt-get install ssh
host# scp -r /home/work/uml/mods/lib/modules/2.6.18/kernel/ 
      root@192.168.1.2:/lib/modules/2.6.18
ubuntu# depmod -a
ubuntu# modprobe xx
ubuntu# rmmod xx