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==Summary==
Based on my previous (unfinished) article on creating a Tiny CentOS distribution, I have created this article. This one is finished (almost). 

As I mentioned earlier. The idea is to have an absolute minimum number of packages. The driving force behind this thought is the latest RedHat Virtualization solution, RHEV, or, RedHat Enterprise Virtualization. RHEV is a slim/cut down version of RHEL 6, working as a KVM Hypervisor, with a very small install foot-print. I noticed that it is a similar concept as Citrix XEN Server. So, I wanted to see, if I can be successful in creating a similar product, based on CentOS 5.5. Notice that the procedure explained below DOES NOT contain libvirt, as yet. This is only because I was first interested in creating a distribution as small as possible. Since I have included yum in it, I (and you) can add any other RPM based package to it, without a problem. In coming days however, I will release a (so called) hypervisor version, InshaAllah (God Willing).

CENTOS/RHEL already has a @core group (option), which can be used in the kickstart based installation. Even that takes up considerable space and installs CUPS, SENDMAIL and a lot of other un-necessary packages. 

Since I wanted to create a very small list of RPMS. I came up with a plan. I started with kernel, and kept trying to install the related RPMS in a temporary directory using RPM. I continued including missing files (RPMS), which were being reported by RPM as required dependencies. When all dependencies got resolved, I believed I had the desired minimal file list. 

When I completed the basic minimal list, I added ssh-server, wget and yum to it. I further added the following: grub (boot loader), openssh-clients (for ssh, scp, sftp, etc), and vim-minimal (editor).

That would essentially make it a working server installation/distribution. Anything else can be added through "yum". The packages size is 108 RPM files (CENTOS), and 124 MB in total. 

Note that I (generated and) tested this on a KVM based VM. This list does not include kernel-xen. You should add kernel-xen RPM to the rpm list, if you intend to use it either as XEN host, or XEN VM. 

==Infrastructure==
===Physical Host===
The physical host is a Fedora 14 machine, with 4 GB RAM, and 200 GB of disk. Out of which about 70 GB is free space.

The disk has a directory /data/cdimages , which hosts various ISO images of different OS, I have. This directory has the following layout (only the part interesting to us is shown below). 

<pre>
[root@fedora14 cdimages]# tree -d
.
├── CentOS-5.5-i386
│   ├── CentOS
│   ├── images
│   │   ├── pxeboot
│   │   └── xen
│   ├── isolinux
│   ├── NOTES
│   └── repodata
└── CentOS-5.5-i386-tiny
</pre>

The /data/cdimages/CentOS-5.5-i386 is the full DVD copied in this directory. If you cannot afford to download full DVD, (for perfectly understandable reasons), you can download the packages, directly from the CENTOS website. The method to do so, is already mentioned here: http://cooker.wbitt.com/index.php/CENTOS_Server_CD_project#Creating_the_.22core.22_install-tree_from_a_http_site

The /data/cdimages/CentOS-5.5-i386-tiny directory shown above, is an empty directory. It is possible that you do not have this directory created at this moment. We can create this directory at a later stage. 

The directory /data/cdimages on the physical host, is made available as an NFS writeable share to the 192.168.122.0/24 network. As following:

<pre>
[root@fedora14 cdimages]# cat /etc/exports
/data/cdimages 192.168.122.0/255.255.255.0(rw,no_root_squash).
[root@fedora14 cdimages]#

[root@fedora14 cdimages]# service nfs restart 
</pre>
(Make sure that the firewall is not blocking incoming NFS requests on the physical host).

This is a good method to save space, both on the physical host and on the VMs. That means, you don't have to "fill-up" your build host (VM) will all the DVD/RPM files and ISO images. So they don't need large virtual disks for it. All of the work, can be performed, when we mount this directory /data/cdimages, from the physical host, to the buildhost-32 VM.

The physical host has the IP: 192.168.122.1 , on the virbr0 interface. It may (or may not) have any IP on it's eth0 interface, which is irrelevant to this text. 

===Build Host===
The buildhost (named buildhost-32) is actually a CentOS 5.5 32 bit Virtual Machine running inside a Fedora 14 physical host. It is installed with the minimal installation available with default CENTOS installer. It has additional packages installed on it, which are: 
<pre>
[root@buildhost-32 ~]# yum -y install anaconda anaconda-runtime mkisofs cdrecord
</pre>
The BuildHost has only 512 MB Virtual Memory, and 2GB Virtual Disk. We basically do not need much disk space on the build host. The BuildHost (VM) has the IP: 192.168.122.94, on its eth0 interface.


==Steps==
===Make the repositories available on the buildhost-32===
See if you are able to view the NFS share made available on the physical host.
<pre>
[root@buildhost-32 ~]# showmount -e 192.168.122.1
Export list for 192.168.122.1:
/data/cdimages 192.168.122.0/255.255.255.0
</pre>

Create a mount point on the build host, and mount the NFS share on it.

<pre>
[root@buildhost-32 ~]# mkdir /mnt/cdimages

[root@buildhost-32 ~]# mount -t nfs 192.168.122.1:/data/cdimages/  /mnt/cdimages/

[root@buildhost-32 ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/vda1             2.8G  913M  1.8G  34% /
tmpfs                 252M     0  252M   0% /dev/shm
192.168.122.1:/data/cdimages/
                      191G  113G   69G  63% /mnt/cdimages
[root@buildhost-32 ~]# 
</pre>

As you can see, the /data/cdimages from the physical host is now available on our buildhost-32, as /mnt/cdimages. 

Create an empty directory CentOS-5.5-i386-tiny inside /mnt/cdimages, if not already done so. It must be empty though. This directory is going to hold our new custom distribution.

<pre>
[root@buildhost-32 ~]# mkdir /mnt/cdimages/CentOS-5.5-i386-tiny
</pre>

Copy the DVD structure, (excluding the CentOS directory), from /mnt/cdimages/CentOS-5.5-i386/ to this newly created directory /mnt/cdimages/CentOS-5.5-i386-tiny/.  
<pre>
[root@buildhost-32 ~]# rsync -av --exclude CentOS/  \
   /mnt/cdimages/CentOS-5.5-i386/   /mnt/cdimages/CentOS-5.5-i386-tiny/
</pre>

Without the CentOS directory, which holds all the RPMs of the distribution, the structure (with some necessary files), is about 226 MB in total.
<pre>
[root@buildhost-32 ~]# du -sh /mnt/cdimages/CentOS-5.5-i386-tiny/
226M	/mnt/cdimages/CentOS-5.5-i386-tiny/
[root@buildhost-32 ~]# 
</pre>

I created a temporary directory named /tmp/rpms, and started copying RPM files one by one from the original source distribution directory (/mnt/cdimages/CentOS-5.5-i386/CentOS) , to this directory. I started with the kernel RPM and kept testing the  installation of the RPMS I copied, in the /tmp/RPMtest directory, which is again, a freshly created empty directory. 

<pre>
[root@buildhost-32 tmp]# mkdir /tmp/rpms

[root@buildhost-32 tmp]# mkdir /tmp/RPMtest
</pre>

Copy one file at a time to the /tmp/rpms directory:
<pre>

[root@buildhost-32 tmp]#  cp /mnt/cdimages/CentOS-5.5-i386/CentOS/kernel-2.6.18-194.el5.i686.rpm   \ 
  /tmp/rpms/
</pre>

Used the following two commands to test install the rpms I placed in /tmp/rpms/ directory. 

<pre>
rpm --initdb --dbpath /tmp/RPMtest/ 
rpm --test --dbpath /tmp/RPMtest/ -ivh /tmp/rpms/*.rpm
</pre>

<pre>
[root@buildhost-32 tmp]# rpm --test --dbpath /tmp/RPMtest/ -ivh /tmp/rpms/*.rpm
warning: /tmp/rpms/kernel-2.6.18-194.el5.i686.rpm: Header V3 DSA signature: NOKEY, key ID e8562897
error: Failed dependencies:
        fileutils is needed by kernel-2.6.18-194.el5.i686
        module-init-tools is needed by kernel-2.6.18-194.el5.i686
        initscripts >= 8.11.1-1 is needed by kernel-2.6.18-194.el5.i686
        mkinitrd >= 4.2.21-1 is needed by kernel-2.6.18-194.el5.i686
        /bin/sh is needed by kernel-2.6.18-194.el5.i686
[root@buildhost-32 tmp]#
</pre>

As you can see, now I need to copy more RPMs in the /tmp/rpms directory, to satisfy the dependencies problems seen above. This is a daunting manual task, as I don't know an automated method to do it, (nor had time to device a script for it).

I created the following script, containing the same two lines to repeatedly test-install the RPMs.
<pre>
[root@buildhost-32 tmp]# cat testrun.sh 
#!/bin/bash
rpm --initdb --dbpath /tmp/RPMtest/ 
rpm --test --dbpath /tmp/RPMtest/ -ivh /tmp/rpms/*.rpm
[root@buildhost-32 rpms]# 
</pre>

Here are the basic stats:

Total packages and size of the RPMs alone:
<pre>
[root@buildhost-32 tmp]# ls -l /mnt/cdimages/CentOS-5.5-i386-tiny/CentOS/ | wc -l
110

Actually 108 packages. (Need to exclude . and .. directories from the list above)

[root@buildhost-32 tmp]# du -sh /mnt/cdimages/CentOS-5.5-i386-tiny/CentOS/ 
124M	/mnt/cdimages/CentOS-5.5-i386-tiny/CentOS/
</pre>


Includes ssh-server, wget and yum:
<pre>
[root@vm2 centos-micro]# ls -1 | sort
audit-libs-1.7.17-3.el5.x86_64.rpm
basesystem-8.0-5.1.1.el5.centos.noarch.rpm
bash-3.2-24.el5.x86_64.rpm
binutils-2.17.50.0.6-14.el5.x86_64.rpm
bzip2-libs-1.0.3-4.el5_2.x86_64.rpm
centos-release-5-5.el5.centos.x86_64.rpm
centos-release-notes-5.5-0.x86_64.rpm
chkconfig-1.3.30.2-2.el5.x86_64.rpm
coreutils-5.97-23.el5_4.2.x86_64.rpm
cpio-2.6-23.el5_4.1.x86_64.rpm
cracklib-2.8.9-3.3.x86_64.rpm
cracklib-dicts-2.8.9-3.3.x86_64.rpm
crontabs-1.10-8.noarch.rpm
db4-4.3.29-10.el5.x86_64.rpm
device-mapper-1.02.39-1.el5.x86_64.rpm
device-mapper-event-1.02.39-1.el5.x86_64.rpm
device-mapper-multipath-0.4.7-34.el5.x86_64.rpm
dmraid-1.0.0.rc13-63.el5.x86_64.rpm
dmraid-events-1.0.0.rc13-63.el5.x86_64.rpm
e2fsprogs-1.39-23.el5.x86_64.rpm
e2fsprogs-libs-1.39-23.el5.x86_64.rpm
elfutils-libelf-0.137-3.el5.x86_64.rpm
ethtool-6-4.el5.x86_64.rpm
expat-1.95.8-8.3.el5_4.2.x86_64.rpm
filesystem-2.4.0-3.el5.x86_64.rpm
findutils-4.2.27-6.el5.x86_64.rpm
fipscheck-1.2.0-1.el5.x86_64.rpm
fipscheck-lib-1.2.0-1.el5.x86_64.rpm
gawk-3.1.5-14.el5.x86_64.rpm
gdbm-1.8.0-26.2.1.x86_64.rpm
glib2-2.12.3-4.el5_3.1.x86_64.rpm
glibc-2.5-49.x86_64.rpm
glibc-common-2.5-49.x86_64.rpm
grep-2.5.1-55.el5.x86_64.rpm
gzip-1.3.5-11.el5.centos.1.x86_64.rpm
hmaccalc-0.9.6-3.el5.x86_64.rpm
info-4.8-14.el5.x86_64.rpm
initscripts-8.45.30-2.el5.centos.x86_64.rpm
iproute-2.6.18-11.el5.x86_64.rpm
iputils-20020927-46.el5.x86_64.rpm
kernel-2.6.18-194.el5.x86_64.rpm
keyutils-libs-1.2-1.el5.x86_64.rpm
kpartx-0.4.7-34.el5.x86_64.rpm
krb5-libs-1.6.1-36.el5_4.1.x86_64.rpm
less-436-2.el5.x86_64.rpm
libacl-2.2.39-6.el5.x86_64.rpm
libattr-2.4.32-1.1.x86_64.rpm
libcap-1.10-26.x86_64.rpm
libgcc-4.1.2-48.el5.x86_64.rpm
libselinux-1.33.4-5.5.el5.x86_64.rpm
libsepol-1.15.2-3.el5.x86_64.rpm
libstdc++-4.1.2-48.el5.x86_64.rpm
libsysfs-2.0.0-6.x86_64.rpm
libtermcap-2.0.8-46.1.x86_64.rpm
libxml2-2.6.26-2.1.2.8.x86_64.rpm
logrotate-3.7.4-9.x86_64.rpm
lvm2-2.02.56-8.el5.x86_64.rpm
m2crypto-0.16-6.el5.6.x86_64.rpm
MAKEDEV-3.23-1.2.x86_64.rpm
mcstrans-0.2.11-3.el5.x86_64.rpm
mingetty-1.07-5.2.2.x86_64.rpm
mkinitrd-5.1.19.6-61.x86_64.rpm
mktemp-1.5-23.2.2.x86_64.rpm
module-init-tools-3.3-0.pre3.1.60.el5.x86_64.rpm
nash-5.1.19.6-61.x86_64.rpm
ncurses-5.5-24.20060715.x86_64.rpm
net-tools-1.60-81.el5.x86_64.rpm
nspr-4.7.6-1.el5_4.x86_64.rpm
nss-3.12.3.99.3-1.el5.centos.2.x86_64.rpm
openssh-4.3p2-41.el5.x86_64.rpm
openssh-server-4.3p2-41.el5.x86_64.rpm
openssl-0.9.8e-12.el5_4.6.x86_64.rpm
pam-0.99.6.2-6.el5_4.1.x86_64.rpm
pcre-6.6-2.el5_1.7.x86_64.rpm
popt-1.10.2.3-18.el5.x86_64.rpm
procps-3.2.7-16.el5.x86_64.rpm
psmisc-22.2-7.x86_64.rpm
python-2.4.3-27.el5.x86_64.rpm
python-elementtree-1.2.6-5.x86_64.rpm
python-iniparse-0.2.3-4.el5.noarch.rpm
python-sqlite-1.1.7-1.2.1.x86_64.rpm
python-urlgrabber-3.1.0-5.el5.noarch.rpm
readline-5.1-3.el5.x86_64.rpm
rpm-4.4.2.3-18.el5.x86_64.rpm
rpm-libs-4.4.2.3-18.el5.x86_64.rpm
rpm-python-4.4.2.3-18.el5.x86_64.rpm
sed-4.1.5-5.fc6.x86_64.rpm
setup-2.5.58-7.el5.noarch.rpm
sgpio-1.2.0_10-2.el5.x86_64.rpm
shadow-utils-4.0.17-15.el5.x86_64.rpm
sqlite-3.3.6-5.x86_64.rpm
sysklogd-1.4.1-46.el5.x86_64.rpm
SysVinit-2.86-15.el5.x86_64.rpm
tar-1.15.1-30.el5.x86_64.rpm
tcp_wrappers-7.6-40.7.el5.x86_64.rpm
termcap-5.5-1.20060701.1.noarch.rpm
testrun.sh
tzdata-2010e-1.el5.noarch.rpm
udev-095-14.21.el5.x86_64.rpm
util-linux-2.13-0.52.el5_4.1.x86_64.rpm
wget-1.11.4-2.el5_4.1.x86_64.rpm
yum-3.2.22-26.el5.centos.noarch.rpm
yum-fastestmirror-1.1.16-14.el5.centos.1.noarch.rpm
yum-metadata-parser-1.1.2-3.el5.centos.x86_64.rpm
zlib-1.2.3-3.x86_64.rpm
[root@vm2 centos-micro]#
</pre>

===Install necessary packages on the buildhost-32===
<pre>
[root@buildhost-32 ~]# yum -y install anaconda anaconda-runtime mkisofs cdrecord
</pre>