User Mode Linux

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> Will I be able to run UML (skas or not) on a plain RH 9 machine?

Yes,

uml tools comes with RH9. you can find some in /usr/bin/uml_* . so, you need to get "linux" command (uml kernel) and config file. from: http://kernels.usermodelinux.org/kernels/ I used linux-2.4.20-6um.

put "linux" in /usr/bin/ as executable. (chmod +x /usr/bin/linux)
put "dotconfig" in /usr/lib/uml/ as "config".

some files need to change the mode. RH9 kept them secure.

# chmod u+s /usr/bin/uml_net
# chmod g+rw,o+rw /dev/net/tun

download disk image file from http://user-mode-linux.sourceforge.net/dl-fs-sf.html I got Debian-3.0r0.ext2.bz2 which is Debian 3.0r0 minimum installation.

I explain with this case.

$ bunzip2 Debian-3.0r0.ext2.bz2

... this fs is almost full, to expand fs to 512mb is...

$ dd if=/dev/zero of=Debian-3.0r0.ext2 bs=1 count=0 seek=512MB 
$ resize2fs -p Debian-3.0r0.ext2 

... starting linux

$ linux ubd0=Debian-3.0r0.ext2.diff,Debian-3.0r0.ext2 eth0=tuntap,,,192.168.1.100

192.168.1.100 is any valid and unused IP on your LAN. you can login as root without password.

set hostname

UML# echo debian.mynet >/etc/hostname
UML# /etc/init.d/hostname.sh

set network

edit /etc/network/interfaces and add these lines:

-----
auto lo eth0

iface lo inet loopback

iface eth0 inet static
   address 192.168.1.101
   netmask 255.255.255.0
   gateway 192.168.1.1
---------

192.168.1.101 is any valid and unused IP address of your network. So, this UML setup uses two IP addresses, one for host side, another for guest side.

edit /etc/resolv.conf and add your name servers.

-------
nameserver 192.168.1.3
nameserver 192.168.1.4
-------

now, you can start network.

# /etc/init.d/network start

you can ping anywhere in the world.

you can access files on the host side.

# mount none /mnt -t hostfs

now, /mnt is the / of host OS. you can read/write.

if you want to install something more, use apt-get. for example, to install apache web server:

# apt-get update
--- to get the latest list of package, then

# apt-get install apache

you can see the test page from your host OS by http://192.168.1.101/

# halt

to shutdown Debian...

from 2nd time, you can start UML without real disk image.

$ linux ubd0=Debian-3.0r0.ext2.diff eth0=tuntap,,,192.168.1.100

love and fun
--Setu 19:51 21 Oct 2003 (JST)

Making file partition bigger

This is very simple. You can read article here.

first, stop UML
halt
make single file from fs file and COW file.
uml_moo Debian-3.0r0.ext2.diff Debian-3.0r0.4gb.ext2
- new fs is Debian-3.0r0.4gb.ext2 in above sample
checking new fs
e2fsck -f filename
making fs for 4GB but it uses around 64MB + "fs system area".
dd if=/dev/zero of=Debian-3.0r0.4gb.ext2 bs=1 count=0 seek=4gb
expand file system
resize2fs -p Debian-3.0r0.4gb.ext2

run it

First time:

linux ubd0=Debian-3.0r0.4gb.ext2.diff,Debian-3.0r0.4gb.ext2 eth0=tuntap,,,192.168.1.100

Second time:

linux ubd0=Debian-3.0r0.4gb.ext2.diff eth0=tuntap,,,192.168.1.100

giving more memory for UML

add option at the command line to start: example: linux mem=64M ubd0=Debian-3.0r0.4gb.ext2.diff eth0=tuntap,,,192.168.1.100

You can read all the command option by "linux --help"

making swap area

Making swap fs, next example is making 128MB swap.

at the host: dd if=/dev/zero of=128mb.swap seek=128 count=1 bs=1M

starting UML with this

linux mem=64M ubd0=Debian-3.0r0.4gb.ext2.diff ubd1=128mb.swap eth0=tuntap,,,192.168.1.100
initialize as swap partition. follows are in UML
mkswap -c /dev/ubd/1

/dev/ubd/1 swap swap defaults 0 0

try..

swapon -av

checking... with "free" command:

free: total used free shared buffers cached; Mem: 61772 22588 39184 0 708 4920; -/+ buffers/cache: 16960 44812; Swap: 132088 0 132088