Basic linux setup

First things first: basic linux installation. From scratch.

Linux kernel 2.6.37

• there is no need for every driver available as a module, what I need is xen-support, basic drivers and some networking. As a baseline, a minimum set of driver compiled in should be sufficient. However, quite a few network-modules would be "nice to have" (tunneling, ipsec, vlan, bonding etc) but not needed for booting, and some of these needs to be modules to be able to provide load-time parameters.
• there is also no need for an initial ram-disk, this will be a small, simple setup with one ext2-partition, and the few drivers needed for boot will be linked into the kernel

I have set up a 4GB logical volume in dom0 for the installation. (Normally I would use iSCSI, but the firewall must be able to boot without any other networking present. Infact, the iSCSI-server expects to get an IP-address from the firewall with DHCP)

BusyBox 1.18.1

I will use BusyBox for basic unix utilities. This has probably been compiled with far more functionality than what is currently needed, but it would be a bother to re-compile just to get that one extra utility. Currently I have included:

• init and related utilities
• basic file-utils and text-utils
• every network-util
• some filesystem-tools

The boot-sequence is very simple:

• init starts all daemons through inittab
• init also starts /etc/init.d/rcS which mounts filesystems and set up networking

Putting it all together

Basic directory structure:

• /etc
• /etc/init.d
• /bin
• /sbin
• /usr
• /usr/bin
• /usr/sbin
• /usr/lib
• /lib
• /var
• /lib64
• /proc
• /dev
• /tmp

I added the following files to /etc:

• fstab
• group
• init.d/rcS
• inittab
• passwd
• shadow
• nsswitch.conf
• resolv.conf

contents of inittab:

::sysinit:/etc/init.d/rcS
::respawn:/sbin/getty -L hvc0 9600 linux
::restart:/sbin/init
::ctrlaltdel:/sbin/reboot
::shutdown:umount -a -r

contents of rcS:

#!/bin/sh

fsck /dev/root
mount -t proc proc /proc
mount -o remount,rw /
#mount -a

hostname firewall2
ip address add dev eth0 local 192.168.32.10/24
ip link set dev eth0 up
ip route add to default via 192.168.32.1

(since everything is mounted in the rc-script, fstab is really not needed)

I put busybox in /bin and ran:

/bin/busybox --install -s

this created symlinks to all busybox commands in /bin, /sbin, /usr/bin and /usr/sbin.

Finally, I copied these libraries from an Ubuntu-installation:

/lib/libm.so.6
/lib/libc.so.6
/lib/libcrypt.so.1
/lib/libdl.so.2
/lib/libnsl.so.1
/lib/libresolv.so.2
/lib/libutil.so.1
/lib/libz.so.1
/lib/libnss_files-2.11.1.so
/lib/libnss_dns-2.11.1.so
/lib64/ld-linux-x86-64.so.2

The kernel itself is not on the guest filesystem, it is started by xen in dom0.