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Old 03-15-2005, 07:30 AM   #1
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Create your own Live Linux CD

These steps will show you how to create a functioning Linux system, with the
latest 2.6 kernel compiled from source, and how to integrate the BusyBox
utilities including the installation of DHCP. Plus, how to compile in the
OpenSSH package. The system will have full ssh capabilities. The techniques
for compiling and installing software can be universally applied to your
own packages. So, once you understand the process, you are free to recreate
your own system -- there is a lot of free space.

On system boot-up a filesystem will be created and the contents from the CD
will be uncompressed and completely loaded into RAM -- the CD could be removed
at this point for boot-up on a second computer. You can take over any PC
assuming you have configured the kernel with the appropriate drivers and
the PC can boot from a CD.

FOR COMPLETE DOCUMENT (Could Not Completely Post Here)

QUICK INSTALL: Confirmation that Everything Works - Before Rolling You Own

Quick step 1:

Download "cdrom_linux_boot_proj1.iso" and burn this iso on your
cdrom. Next, reboot the system. This is a check to see if the
current kernel has been compiled with the necessary network,
video, and keyboard (USB included) drivers. If critical drivers
are not recognized they can be added into the kernel.

Quick step 2:

Download the complete project environment "proj1.tar.gz." This includes
everything used to build and customize "cdrom_linux_boot_proj1.iso",
including the BusyBox source, libraries, and ssh. The directory "_install"
contains the necessary libraries for ssh, init and tcpdump. The 2.6.11
kernel ".config" can be found in the documents directory. The staging area
contains a copy of the kernel bzImage, along with the isolinux boot loader.
The "proj1.tar.gz" file is about 13M, since it includes everything
you need, except the kernel source, which can be downloaded from the
following link:

Step 8 covers the configuration and installation of the latest kernel. At
this stage, download the project environment "proj1.tar.gz" from the
following link:

You must "tar -xzf" this file as root to get all the necessary character and
block devices. Standard user accounts cannot create all the necessary block
and character devices that will be needed. Try "tar -xzf" under an account
without root privileges to see the differences in the files created under

If you're curious about the difference between character devices and block
devices, you may want to reference the Linux Journal article

In summary, only block devices can mount filesystems. But character devices,
such as a tape drive can contain data found on a block device.

Checking the download:

a. Check the md5sum to make sure you got the full copy, then,
"tar -xzf" the package.

$ md5sum proj1.tar.gz

b. Now as root, so that you will get all "dev/" devices, execute
the following command.

[Must be done as root]
$ su -
# cd <to project directory>
# tar -xzf proj1.tar.gz

If you did the above as root, then you should have the following:

[root@third-fl-71 _install]# ls -l dev
total 8
crw------- 1 root root 5, 1 Feb 25 20:41 console
lrwxrwxrwx 1 root root 11 Mar 6 09:22 core -> /proc/kcore
brw-rw-rw- 1 root floppy 2, 0 Feb 20 17:37 fd0
brw-rw---- 1 root disk 3, 0 Mar 5 04:32 hda
brw-rw---- 1 root disk 3, 1 Mar 5 20:37 hda1
brw-rw---- 1 root disk 3, 2 Mar 5 20:38 hda2
brw-rw---- 1 root disk 3, 3 Mar 5 21:02 hda3
brw-rw---- 1 root disk 3, 4 Mar 5 21:02 hda4
drwxr-xr-x 2 root root 4096 Mar 5 21:13 mapper
crw-rw-rw- 1 root root 1, 3 Feb 20 17:37 null
crw-rw-rw- 1 root tty 5, 2 Feb 26 12:54 ptmx
drwxr-xr-x 2 root root 4096 Mar 4 05:33 pts
brw------- 1 root disk 1, 0 Feb 20 17:37 ram0
brw-rw-rw- 1 root disk 1, 1 Feb 20 17:37 ram1
brw-rw-rw- 1 root disk 1, 2 Feb 20 17:37 ram2
brw-rw-rw- 1 root disk 1, 3 Feb 20 17:37 ram3
crw-rw-rw- 1 root root 1, 8 Feb 26 03:23 random
brw-rw---- 1 root disk 8, 0 Mar 5 04:32 sda
brw-rw---- 1 root disk 8, 1 Mar 5 04:32 sda1
brw-rw---- 1 root disk 8, 2 Mar 5 04:32 sda2
brw-rw---- 1 root disk 8, 3 Mar 5 21:02 sda3
brw-rw---- 1 root disk 8, 4 Mar 5 21:02 sda4
lrwxrwxrwx 1 root root 15 Mar 6 09:22 stderr -> /proc/self/fd/2
lrwxrwxrwx 1 root root 15 Mar 6 09:22 stdin -> /proc/self/fd/0
lrwxrwxrwx 1 root root 15 Mar 6 09:22 stdout -> /proc/self/fd/1
crw-rw-rw- 1 root root 5, 0 Feb 21 18:32 tty
crw-rw-rw- 1 root root 4, 0 Feb 20 17:37 tty0
crw-rw-rw- 1 root root 4, 1 Feb 20 22:38 tty1
crw-rw-rw- 1 root root 4, 2 Feb 26 08:24 tty2
crw-rw-rw- 1 root root 4, 3 Feb 26 08:24 tty3
crw-rw-rw- 1 root root 4, 4 Feb 26 08:24 tty4
crw-rw-rw- 1 root root 4, 5 Feb 26 08:24 tty5
crw------- 1 root root 4, 6 Mar 1 19:34 tty6
crw-rw---- 1 root root 4, 7 Mar 1 14:33 tty7
crw-rw---- 1 root root 4, 8 Mar 1 14:33 tty8
crw-rw---- 1 root tty 4, 9 Mar 1 14:33 tty9
cr--r--r-- 1 root root 1, 9 Feb 26 03:23 urandom
crw------- 1 vcsa tty 7, 0 Mar 1 14:33 vcs
crw-rw-rw- 1 root root 1, 5 Feb 26 03:23 zero

If you repeat the steps above using a standard account, a lot of the
files will be missing.

c. Take a look at the file "proj1/createiso". This will create
a filesystem on a loop back device with the mount point "./cdrom".
Copy the contents of "_install", which has already been compiled
with the necessary busybox code. Once it is copied, umount "./cdrom" so
that it can be compressed. This will then get copied to the staging area where
"mkisofs" will create a bootable CD image. The boot loader isolinux, along
with the needed config files can be found in "proj1/staging_iso_image/boot/isolinux/"

There is a bash script "createiso" that performs the above tasks.

$ cd proj1
$ su
# ./createiso

Take a look at "createiso". This bash script creates a virtual filesystem.
For details on creating a virtual filesystem reference the following
article on Freshmeat [ ]

COMPREHENSIVE TUTORIAL: Building Everything from Downloaded Source

You may want to keep the results of the quick install steps above in a separate
directory to compare against the completion of each step below.

STEP 1: Download BusyBox

Download BusyBox ( These examples
were created with

$ wget
$ wget
$ md5sum busybox-1.00.tar.gz
fa62459e098fc00b22772aaf2e75bc98 busybox-1.00.tar.gz

Next expand the files:

$ tar -xzf busybox-1.00.tar.gz

Note if you want to verify Erik's key:
$ wget
$ gpg --import gpg.asc
$ gpg --verify busybox-1.00.tar.gz.sign

Now look inside busybox-1.00.tar.gz.sign for the md5sum. Note, he has
done it differently than it's done with the 2.6 kernel (reference step 9).

STEP 2: Configuring BusyBox

You may want to download my config for BusyBox and
rename it to ".config". I have the needed features turned on.

My config download can be found here:

$ cd busybox-1.00

[Note you may need to select another mirror]
$ wget
$ cp chiricobusybox.config .config

You should take a look at the options that I have set by running "make menuconfig"
or take a look at "chiricobusybox.config" directly.

$ make menuconfig

In particular, "Support version 2.6.x Linux kernels" is checked. Under
"Login/Password Management Utilities" everything is checked EXCEPT
"Use internal password and group functions". Note, at this stage you
do NOT want to select this option because "/etc/passwd",
"/etc/shadow" and "/etc/shadow-", will be copied to the "_install/etc"
directory, and used instead.

Also, "lsmod", "modprobe", "rmmod" are checked. Although not essential for the
initial build, this system, you are building, will support networking. You may
eventually want to scp in modules and load them, once you get the system running, of
course. There is plenty of space for these modules.

After taking a look at ".config", run "make" and "make install", which by default
will install everything under "_install".

$ make
$ make install

During the final stages of "make install" the following message will be displayed.

You will probably need to make your busybox binary
setuid root to ensure all configured applets will
work properly.

The next command must be executed after each "make install" to setuid root on the
BusyBox binary.

$ chmod 4755 ./_install/bin/busybox

STEP 3: Needed Directories

Several directories need to be created under "_install". Take
a look at the current contents.

$ cd _install
$ ls
bin linuxrc sbin usr

Next create "dev" for "device entries", which will be
populated later, "etc", "lib", "proc", "tmp", "var" and "sys" with
the following commands.

$ mkdir -p dev sys etc/init.d lib proc tmp var/lib/misc var/lock var/log var/run var/tmp
$ chmod 1777 tmp
$ chmod 1777 var/tmp

STEP 4: Device Entries

The "dev" directory needs to be populated with device entries. They can either be copied
from the current system or created with the "mknod -m " command. The following
will have to be done as root.

Since there are a lot of files, and you may want to rebuild you "_install", it
is recommended that these be put in a file. Below the file "createdev" is
created with the following contents:

# put this in a file called createdev
cp -avp /dev/console dev
cp -avp /dev/core dev
cp -avp /dev/fd0 dev
cp -avp /dev/null dev
cp -avp /dev/ptmx dev
cp -avp /dev/pts dev
cp -avp /dev/ram0 dev
cp -avp /dev/ram1 dev
cp -avp /dev/ram2 dev
cp -avp /dev/ram3 dev
cp -avp /dev/random dev
cp -avp /dev/stderr dev
cp -avp /dev/stdin dev
cp -avp /dev/stdout dev
cp -avp /dev/tty dev
cp -avp /dev/tty0 dev
cp -avp /dev/tty1 dev
cp -avp /dev/tty2 dev
cp -avp /dev/tty3 dev
cp -avp /dev/tty4 dev
cp -avp /dev/tty5 dev
cp -avp /dev/tty6 dev
cp -avp /dev/tty7 dev
cp -avp /dev/tty8 dev
cp -avp /dev/tty9 dev
cp -avp /dev/urandom dev
cp -avp /dev/vcs dev
cp -avp /dev/zero dev

Now run the command, as root, in "_install"

$ su
# pwd

# chmod 700 createdev
# ./createdev

The "ls -al" command now shows the following contents.

# ls -l dev
total 4
crw------- 1 root root 5, 1 Feb 17 14:49 console
crw------- 1 root root 1, 6 Jan 30 2003 core
brw-rw---- 1 root floppy 2, 0 Jan 30 2003 fd0
crw-rw-rw- 1 root root 1, 3 Jan 30 2003 null
crw-rw-rw- 1 root root 5, 2 Mar 5 17:16 ptmx
drwxr-xr-x 2 root root 4096 Feb 17 09:48 pts
brw-rw---- 1 root disk 1, 0 Jan 30 2003 ram0
brw-rw---- 1 root disk 1, 1 Jan 30 2003 ram1
brw-rw---- 1 root disk 1, 2 Jan 30 2003 ram2
brw-rw---- 1 root disk 1, 3 Jan 30 2003 ram3
crw-r--r-- 1 root root 1, 8 Jan 30 2003 random
lrwxr-xr-x 1 root root 17 Mar 5 17:16 stderr -> ../proc/self/fd/2
lrwxr-xr-x 1 root root 17 Mar 5 17:16 stdin -> ../proc/self/fd/0
lrwxr-xr-x 1 root root 17 Mar 5 17:16 stdout -> ../proc/self/fd/1
crw-rw-rw- 1 root root 5, 0 Mar 3 21:20 tty
crw--w---- 1 root root 4, 0 Jan 30 2003 tty0
crw------- 1 root root 4, 1 Feb 17 14:49 tty1
crw------- 1 root root 4, 2 Feb 17 14:49 tty2
crw------- 1 root root 4, 3 Feb 17 14:49 tty3
crw------- 1 root root 4, 4 Feb 17 14:49 tty4
crw------- 1 root root 4, 5 Feb 17 14:49 tty5
crw------- 1 root root 4, 6 Feb 17 14:49 tty6
crw--w---- 1 root root 4, 7 Oct 24 2003 tty7
crw--w---- 1 root root 4, 8 Jan 30 2003 tty8
crw--w---- 1 root tty 4, 9 Jan 30 2003 tty9
crw-r--r-- 1 root root 1, 9 Feb 17 14:49 urandom
crw--w---- 1 vcsa tty 7, 0 Jan 30 2003 vcs
crw-rw-rw- 1 root root 1, 5 Jan 30 2003 zero

These files could all have been created with the "mknod" command. Taking a look
at "tty" above, about half way down, it is a character device with a major number of 5 and
a minor number of 0. It has rights rw-rw-rw. So the "tty" device could have been
created with the command "mknod -m 666 dev/tty c 5 0" .

So, if you want to mount disk drives, ide (hda) and scsi (sda) consider executing
the following commands:

mknod -m 660 dev/hda b 3 0
mknod -m 660 dev/hda1 b 3 1
mknod -m 660 dev/hda2 b 3 2
mknod -m 660 dev/hda3 b 3 3
mknod -m 660 dev/hda4 b 3 4
chown root.disk dev/hda*

mknod -m 660 dev/sda b 8 0
mknod -m 660 dev/sda1 b 8 1
mknod -m 660 dev/sda2 b 8 2
mknod -m 660 dev/sda2 b 8 3
mknod -m 660 dev/sda2 b 8 4
chown root.disk dev/sda*

After the PC is booted from the CD, you can mount these devices after creating a
directory as the mount point "mkdir /h", then, it gets mounted
as "mount -t ext2 /dev/hda2 /h".

It is also possible to create volume groups

mkdir -p dev/mapper
mknod -m 600 dev/mapper/VolGroup00-LogVol00 b 253 0
mknod -m 600 dev/mapper/VolGroup00-LogVol01 b 253 1
chown -R root.root dev/mapper

Create a directory "/v1"

mkdir -p /v1

The VolGroup would be mounted as ext3, most likely by doing
the following after creating a mount point "/v1", then,
"mount -t ext3 /dev/VolGroup00/LogVol01 /v1". But, would require the
proper device drivers to be loaded in the kernel module, and the
needed configuration in "/etc/rc.sysinit", notably the section
under "# LVM2 initializtion". All of this will be discussed in a
future update of this article.

STEP 5: Needed Files and Directories (files and directories in "etc" and "var")

Create the necessary files in "etc". Exit out of root at this point, so
that there is no chance of over-writing you system "/etc" -- note disaster
is only a "/" away. WARNING: Never copy anything into a directory that starts
with "/", since that is your current running system.

[Exit out of root]

The "etc/passwd" file is shown below. Since the ssh daemon will
run, an account will be created for it. Note for sshd that login is set
to "/bin/false"

root:x:0:0:Linux User,,,:/root:/bin/sh
sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/bin/false

Below "root" and "sshd" have been added to the group.


Note below that there is a password for the account root. This encrypted
password is "root". You could create your own password here by copying an
existing account password from "/etc/shadow" and "/etc/shadow-".
The account "sshd" should have "*" for the password.



Interesting question regarding sshd: Why is "/dev/pts" necessary when
sshing into this computer? If you are uncertain, remove this line and
observe the results of the command "ps aux", when attempting to ssh in.

/dev/ram0 / ext2 defaults 0 0
proc /proc proc defaults 0 0
sysfs /sys sysfs defaults 0 0
none /dev/pts devpts gid=5,mode=620 0 0

The file "etc/inittab" is called by the init program. There are no run
levels with BusyBox. The lines "tty2::respawn:/sbin/getty 38400 tty2"
allow you to enter "ctl-alt-F2" and get a login screen.

# This is run first except when booting in single-user mode.
::respawn:/sbin/getty 38400 tty1
# /sbin/getty invocations for selected ttys
#tty1::respawn:/sbin/getty 38400 tty1
tty2::respawn:/sbin/getty 38400 tty2
tty3::respawn:/sbin/getty 38400 tty3
tty4::respawn:/sbin/getty 38400 tty4
tty5::respawn:/sbin/getty 38400 tty5
tty6::respawn:/sbin/getty 38400 tty6
tty7::respawn:/sbin/getty 38400 tty7
tty8::respawn:/sbin/getty 38400 tty8
tty9::respawn:/sbin/getty 38400 tty9
# Example of how to put a getty on a serial line (for a terminal)
#::respawn:/sbin/getty -L ttyS0 9600 vt100
#::respawn:/sbin/getty -L ttyS1 9600 vt100
# Example how to put a getty on a modem line.
#::respawn:/sbin/getty 57600 ttyS2
# Stuff to do when restarting the init process
# Stuff to do before rebooting
::shutdown:/bin/umount -a -r
::shutdown:/sbin/swapoff -a

Note above, "inittab" calls "etc/init.d/rcS". The ram drive
must be remounted; otherwise, it will be read only. Also, when the
system boots, DHCP will be enabled. If the computer is not going to
be connected to the network, comment this out, since it
will repeatedly attempt to acquire an IP address. Also, if
the proper NIC (Network Interface Card) is not found, you will
inundated with messages.

/bin/mount -a
# below getting rid of ram being mounted ro
/bin/mount -o remount /
# The following is for dhcp
ifconfig eth0
# Instead, if you want static IP address
#ifconfig eth0 netmask
#route add default gw
# Run ssh daemon

The file below, along with libraries /lib/libnss_* are necessary for
password authentication, since the recent version of GNU Libc (glibc)
uses Name Service Switch (NSS). This file can probably be copied
from your system's "/etc/nsswitch.conf" file. If you don't have this
file on your system, take the necessary files from "proj1.tar.gz".

# /etc/nsswitch.conf
# An example Name Service Switch config file. This file should be
# sorted with the most-used services at the beginning.
# The entry '[NOTFOUND=return]' means that the search for an
# entry should stop if the search in the previous entry turned
# up nothing. Note that if the search failed due to some other reason
# (like no NIS server responding) then the search continues with the
# next entry.
# Legal entries are:
# nisplus or nis+ Use NIS+ (NIS version 3)
# nis or yp Use NIS (NIS version 2), also called YP
# dns Use DNS (Domain Name Service)
# files Use the local files
# db Use the local database (.db) files
# compat Use NIS on compat mode
# hesiod Use Hesiod for user lookups
# [NOTFOUND=return] Stop searching if not found so far
# To use db, put the "db" in front of "files" for entries you want to be
# looked up first in the databases
# Example:
#passwd: db files nisplus nis
#shadow: db files nisplus nis
#group: db files nisplus nis
passwd: files
shadow: files
group: files
#hosts: db files nisplus nis dns
hosts: files dns
# Example - obey only what nisplus tells us...
#services: nisplus [NOTFOUND=return] files
#networks: nisplus [NOTFOUND=return] files
#protocols: nisplus [NOTFOUND=return] files
#rpc: nisplus [NOTFOUND=return] files
#ethers: nisplus [NOTFOUND=return] files
#netmasks: nisplus [NOTFOUND=return] files
bootparams: nisplus [NOTFOUND=return] files
ethers: files
netmasks: files
networks: files
protocols: files
rpc: files
services: files
netgroup: files
publickey: nisplus
automount: files
aliases: files nisplus

This file contains device names that permit root logins. For now,
it makes sense for root to have lots of capabilities, for testing.
"vc/1","vc/2" stands for virtual consoles.


Below is a minimal hosts file. If you are running on a local LAN without
a DNS server, then, add in additional names. Note, if you ping localhost
and get nothing, then, lo may need to be configured: "ifconfig lo".
If you are not sure what is defined where "ifconfig" will give you a listing.

[etc/hosts] localhost
# Additional names can be added
# squeezel

This is BusyBox's minimal conf.

su = ssx root.0 # applet su can be run by anyone and runs with euid=0/egid=0
su = ssx # exactly the same

The following is used for acquiring an IP address via dhcp. The important
setting here is the interface, which should be set to "eth0". The script that
gets run "_install/usr/share/udhcpc/default.script" is the default BusyBox
script for acquiring a dhcp address. Note, "etc/init.d/rcS" runs "/sbin/udhcpc",
on bootup. You could remove this and assign a static IP address instead.

FOR COMPLETE DOCUMENT (Could Not Completely Post Here)
Old 03-15-2005, 07:38 AM   #2
Bruce Hill
HCL Maintainer
Registered: Jun 2003
Location: McCalla, AL, USA
Distribution: Gentoo (all servers at work are openSUSE)
Posts: 6,931

Rep: Reputation: 128Reputation: 128
Forest, I think you got the wrong forum...
Old 03-15-2005, 08:38 AM   #3
Registered: Nov 2002
Location: Kent, England
Distribution: Debian Testing
Posts: 19,192
Blog Entries: 4

Rep: Reputation: 472Reputation: 472Reputation: 472Reputation: 472Reputation: 472
Cool how to, but it would go better (and more completely) in Tutorials. Could I ask that you submit it there so it doesn't get lost among the other posts.


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