CentOS 6 Basic Install

There are a lot of new options to explore in CentOS 6 during install, be sure that you have a basic understand of what the options are before you begin the installation. One important aspect is to understand what type of hardware will be used for the server, hardware or software RAID, LVM, ext3 or ext4, etc.

Upgrades vs. Migration

An upgrade can be performed over the minor distribution increments. In other words, the software supports upgrading from a CentOS 5.6 to 5.7. However, upgrades between major versions CentOS 5 to 6 is not recommended. Many applications are modified between the major versions and will not maintain the settings and custom configuration that was used previously. Not to say it has not been done, it is not recommended and can lead to system problems. These situations, CentOS 5 to 6, would require a migration of the settings. In other words, all of the applications would be installed in CentOS 6 as were installed in CentOS 5 but they would require a fresh install on a clean system, not an upgrade. Any applications which were installed on the older version should have the settings migrated to the new system.

One thing that may be important to do in this process is to create a file that can be used as a reference in terms of the package versions that are installed so it is easier to troubleshoot later.

rpm -qa --qf '%{NAME} %{VERSION}-%{RELEASE} %{ARCH}\n' > pkglist.txt

centos-release-notes 5.5-0 i386

mktemp 1.5-23.2.2 i386

db4 4.3.29-10.el5_5.2 i386

libcap 1.10-26 i386

gdbm 1.8.0-26.2.1 i386

libsysfs 2.0.0-6 i386

libjpeg 6b-37 i386

perl-Convert-ASN1 0.20-1.1 noarch

file 4.17-15.el5_3.1 i386

---cut---

A clean install is preferable when you are going to install a server. A clean install means that you are not updating a system, this is a completely new install or the old hard drive is erased so that it functions as a new installation. Upgrades will often lead to old files with conflicts and old problems that need to be removed.

One of the first options you will see besides language and keyboard options is to determine “Storage Devices”. If you are using SATA or SCSI drives attached to the local machine the “Basic” option is the one to choose. If you are using other options like installing in a SAN, Firmware RAID, or iSCSI select the “Specialized” option. The fist option to explore is the “Basic Storage Devices”.

Basic Storage Devices

Install Minimal System Using Default Partitioning

This road map represents the decisions made to complete a minimal install with the defaults (choices highlighted).

Basic Storage Devices

Installation Type

Use All Space

Creates Default Partitions

(/, /home, SWAP - all LVM)

Desktop

Minimal Desktop

Minimal

Encrypt system

Review and modify partitioning layout

If you are using the “Basic” option, as in this example, then select that and choose “Next” which will lead to the screen to set the hostname and the networking options. If possible set the hostname as a Fully Qualified Domain Name (FQDN) as illustrated in the example, hostname and domain. The FQDN will be useful in locating this machine on your network.

Here the domain is localnet, it could easily be something like this example:

mail.example.com

The next step is to configure the networking aspect. Edit the system network cards that are detected. In this example eth0 is the only network card detected. Your server may have multiple network cards so you will need to determine which network card is the one that will be used by the internal and external networks. Servers do not typically use wireless or Mobile Broadband.

The other variation is that if this machine is a virtual machine the name of the network connection could be a number of things like venet0 instead of eth0. The name will depend on the type of virtualization that you are using.

The network card must have a static or “Manual” IP Address as you do not want to have this IP Address change. Be sure to list the IP, the netmask and the gateway. In this example the netmask number “24” includes all of the machines on the 192.168.5.0 network (255 machines) and is the same as saying 255.255.255.255. The gateway is the IP Address that Nagios will use to access the Internet. This is important for updates to the system.

The server will need a DNS server to help resolve addresses for updates and for connecting to other machines as well as for sending mail.

The only real option on a server is to “Use All Space” and remove all other system files to maintain the integrity of the installation. Certainly if this disk has been used previously you will want to destroy all previous data and create a clean install. If you want to create a custom layout select the last option.

Once you select the “Use All Space” option you will need to decide which drive you want to use in order to create the installation. The drive that is intended to receive the install should be moved into the “Target Devices”. Whatever devices you want to use for data can remain in the “Data Storage Devices”.

Whenever you create a server it is important to think about backups, redundancy and disk space growth at install. In this example there are two drives so the decision will be how to use that second drive to your advantage. If there is hardware RAID that support redundancy then this is not as critical decision. But if all you have is two drives you may consider using one drive as a backup drive so that if you have catastrophic failure on the primary drive you do have the files you need to rebuild quickly. The other option of course is to use the extra drive with LVM so that the entire system could be expanded if you needed.

The default install will create a boot partition, and two logical volumes for / and for /home. This type of set up will work OK for a basic installation. However, the separate partition for /home is probably not needed unless you will be creating a file server.

df

Filesystem 1K-blocks Used Available Use% Mounted on

/dev/mapper/vg_centos-lv_root

51606140 662756 48321944 2% /

tmpfs 255784 0 255784 0% /dev/shm

/dev/sda1 495844 27641 442603 6% /boot

/dev/mapper/vg_centos-lv_home

50065640 184136 47338300 1% /home

A minimal installation is all that is required for CentOS server as you can always use yum to install needed applications with yum.

Desktop - graphical desktop

Minimal - single-purpose install with as little as installed as possible

Basic Server - base system to use as typical server

Database Server - MySQL and PostgreSQL are loaded on the server

Web Server - Apache web server

Virtual Host - uses KVM and Virtual Machine Manager to create host for virutal machines

Software Development Workstation - installs all of the tools required to compile software

Adding Repositories

This section is designed to allow you to use additional repositories to add additional options to the server like high availability, load balancing, etc. This is not specifically designed for 3rd party repositories.

This basic install should provide a foundation for most basic installations.