Red Hat Enterprise Linux 6 coming soon

Red Hat, a company that holds a large portion of the Linux server market, recently released the latest version of their OS, Red Hat Enterprise Linux 5.5. The first version of the 5.x series was released in 2007, and now RHEL 6 is said to be released soon.

RHEL is the child of Red Hat Linux, which was primarily a consumer Linux distribution, but many system administrators used it for enterprise-level web hosting servers. Eventually, Red Hat decided to cash in on the enterprise market and developed RHEL. To keep the consumer Linux users happy, they also released Fedora, a community-driven version of the same operating system.

Fedora’s development line is faster and usually has newer packages. Some system administrators who want cutting-edge technology, still use Fedora for web hosting. But for many businesses that want stable long-term releases, RHEL has been their reliable choice. Some of the improvements in version 5.5 include support for latest hardware, better virtualization support, and improved memory management. Red Hat has an annual revenue of $653 million.

Image Source: Wikimedia Commons

How to install OpenVZ with yum

OpenVZ is a free and open source virtualization solution for Linux. Here is an easy guide to installing OpenVZ on Redhat Enterprise Linux, CentOS, or Fedora.

Note: It is recommended that you use an ext2 or ext3 file system if you want per-container disk quota.

1. Add the OpenVZ YUM repository:

# cd /etc/yum.repos.d
# wget http://download.openvz.org/openvz.repo
# rpm --import http://download.openvz.org/RPM-GPG-Key-OpenVZ

2. Find out which kernel version you need and install it:

# yum install ovzkernel[-flavor]

3. Change the new GRUB bootloader lines created when you installed the kernel to look something like this in /boot/grub/grub.conf:

title OpenVZ (2.6.8-022stab029.1)
root (hd0,0)
kernel /vmlinuz-2.6.8-022stab029.1 ro root=/dev/sda5
initrd /initrd-2.6.8-022stab029.1.img

That’s it! You now have OpenVZ installed. Visit the OpenVZ wiki for more information about configuring your new installation.

Source: OpenVZ Quick Installation

How to install Nginx via YUM in CentOS

Nginx (pronounced “Engine X”) is a lightweight web server that offers speed and flexibility without all of the extra features that larger web servers like Apache offer. Although it is a free and open source application, CentOS does not offer the latest version in its default YUM repository. To install it, you need to add the EPEL (Extra Packages for Enterprise Linux) repository, which is part of the Fedora Project.

1. Install the EPEL repository:

# rpm -Uvh http://download.fedora.redhat.com/pub/epel/5Server/x86_64/epel-release-5-3.noarch.rpm

2. Install nginx

# yum install nginx

3. You will be asked to install the gpg-key for EPEL. Answer yes

4. Start Nginx

# /etc/init.d/nginx start

5. Check the installation by going to your web server’s default site, either using your ip address or domain name.

How to delete duplicate files in Linux

Question: Two of my directories on my server have some the same files. How can I easily delete any duplicates while preserving the unique files?

Answer: There exists a Linux tool for just about everything, and this is no exception. You need a tool called fdupes, which searches the path you give it for duplicate files and uses several comparison techniques (sizes, MD5 signatures, byte-by-byte comparison) to find and eliminate duplicates.

First install fdupes. In RHEL/Fedora/CentOS, use the rpmforge repository enter:

# yum install fdupes

To find duplicates in the /etc directory, you would enter:

# fdupes /etc

To force fdupes to prompt you whether to preserve or delete files:

#fdupes -d /etc

As you can see, fdupes might be just what you need to clean up your server and possibly increase that precious disk space.

Source: nixCraft
Photo: Wikimedia Commons

Managing bootup services on Linux servers

Question: Which Linux services should be enabled at boot on a server?

Answer: Most Linux distributions come with more than what you need. They are designed to not only work on servers but also desktop computers, laptops, netbooks, and in some cases, even smaller mobile devices like phones. Because of this there are sometimes numerous services running that you may not need. Similarly, there might be special server-oriented services that you will want to enable.

Security is also an issue. In the past we covered X.org and why it is a bad idea to have it running on a server. There are other services like X.org that might be good for the desktop but are superfluous on a server. The first thing to do is to find out which services are currently running. Execute the following commands:

#service --status-all
#chkconfig --list | grep '3:on'

You can read the rest of the steps in tis process at nixCraft. Everything in the complete how-to article will cover CentOS, Fedora, and Redhat Enterprise Linux.

Source: nixCraft

How to install and configure ProFTPD in RHEL/CentOS/Fedora Linux

ProFTPD is one of the most widely used and trust Linux-based FTP servers. When installed on a dedicated server, ProFTPD can act as a virtual ftp server host to multiple user accounts. It also allows anonymous FTP, if needed, chroot jail support, SSL/TLS encryption, and much more.

nixCraft has an excellent tutorial for installation and configuration of ProFTPD in CentOS, Redhat Enterprise Linux, and Fedora.

To install ProfFTPD, type the following as root:

# yum install proftpd

To make ProFTPD start whenever the system boots, enter:

# chkconfig --level 3 proftpd on

To start it immediately, type:

# service proftpd start

Read the rest of the nixCraft article.

The sysconfig directory in Redhat-based Linux

Redhat Enterprise Linux, Fedora, and Centos have a convenient directory called “sysconfig”. It is located under the main /etc directory and contains many of the frequently-used configuration files necessary to operate a server. Often the configuration files are for command line options or very specific settings rather than the complete settings for a particular application.

For example, the httpd file under sysconfig is the configuration for the httpd server rather than Apache as a whole. In it you can set startup options and command flags. Other configuration files include crond (for configuring the crontab frequency), syslog (which configures the system log rotation), and spamassassin (setup for the spam filtering service).

One of the most important folders in sysconfig is “networking“. This is where a user sets up network devices, and devices that are automatically setup appear here as well. You would only need to configure this file if you were running a locally housed server. If your server is remote, this will never need to be changed and attempting to change it could cause you to lose the ability to access the server at all. I recommend browsing through the complete list of files in /etc/sysconfig and at least becoming aware of them, in case you need one of them in the future.

Fixing YUM Dependency Problems: Part 1

Question: YUM is telling me I have broken dependencies. I can’t install anything. Help!

Answer: Fiddling with your server can lead you to problems, very serious ones if it lands you in what is affectionately called RPM Hell. This usually happens when you download an RPM outside of your standard distribution repository and install it over top of your current Linux distribution. For example, you might be running CentOS and install a Fedora package that has a different set of dependencies.

Hopefully, if you are reading this, you were just curious and have not taken that plunge. If so, heed the warning and think twice before you grab any RPM you can find and start plugging it in to your server hosting all of your hard-earned websites. If you have already sent YUM into fits, all hope is not lost. First, try uninstalling whatever started the problem. In some cases, all you need to do is clean YUM:

yum clean all

You can also ignore dependencies until you can install whatever packages you need to remedy the situation.

From the command line, enter:

yum --skip-broken update

Continued in Part 2…

Photo Source: Flickr

How to reinstall packages with YUM

Question: One of my applications in CentOS Linux is not working right. How do I reinstall it?

Answer: Early version of YUM did not have a “reinstall” function, but the newest version do. To reinstall a package, simply type as root:

yum reinstall package-name

If you are running a server with an older version of Fedora or other Redhat-based Linux distribution, your version of YUM may not support reinstallation. In such a case, you will have to manually reinstall it. From root, enter a command such as this to remove the files from the database:

rpm -e --justdb --nodeps packagename

YUM will then believe the package is not installed, even though it still is. Install as you normally would with:

yum install package-name

Making YUM Faster

Question: When I run updates with YUM (an update tool for Redhat, CentOS, or Fedora Linux), it seems like it takes forever. How can I make it faster?

Answer: Although there many things to consider when trouble-shooting speed issues, one specific YUM concern might be the speed of the mirror sites used for downloading packages. If download time seems to be the main concern (as opposed to actual installation time), installing yum-fastmirror should help.

This simple program will automatically seek out the fastest YUM mirror servers and then store the metadata in /var/cache/yum/timedhosts.txt. The plugin works by timing all the servers that come up in the mirror list and then selecting the one that is fastest for your location. Locations closer to you on less congested servers usually connect and send data faster. With yum-fastmirror, this can all be configured automatically.

To install the plugin, enter as root:

yum install yum-fastmirror