• FAQ
• CentOS5

Questions about CentOS 5

1. What is the "Server" and what is the "Path" when I try to do a network install?

If you desire to do a remote HTTP or FTP install from the Internet using the LiveCD or the netinstall.iso, you can pick a mirror that is close to you from these public mirrors:

http://www.centos.org/modules/tinycontent/index.php?id=13

You can then find the path on that mirror to the "5/os/<arch>/" directory and use the paths for install where <arch> is the desired architecture (i386 or x86_64 for example). If you want to choose the mirror provided by "Linux Kernel Archives", in the above page click on the HTTP link for that mirror, then click 5 -> i386 -> os ... the full path for this mirror would be:

http://mirrors.kernel.org/centos/5/os/i386/

In the HTTP installation, use these paths based on the above mirror:

Server: mirrors.kernel.org
Path:   centos/5/os/i386

Other install locations are available by selecting a mirror close to you.

2. I get a yum error "TypeError: unsubscriptable object"

It is not quite clear what leads to this error at the moment. You can work around it by issuing yum clean all on the command line and then try again. This should resolve the error. See this CentOS bug report and this Bug report at Red Hat.

This issue is fixed in CentOS-5.4

3. Can I install CentOS 5 with just the first CD?

You can do a minimal install that just requires the first CD by performing the following two steps during the installation:

• During the category/task selection, deselect all package categories, and choose the "Customize now" option at the bottom of screen.

• During the customized package selection, deselect everything ( including the Base group ).

There are reports that more than CD 1 is required in the following case:

• If you use some software raid options (this will also require CD 2 and 5)
• If you use encrypted filesystems

When the anaconda installer notes that additional disks will be required but you desire a one CD install, the quick answer is one or more of the following approaches:

• Trim back and do a minimal install. Then once the install is up and running, pull in more packages with yum and add more options later.

If you want to avoid using more than one CD but want to install more than just the minimal set of packages, you could also consider doing a network installation. A network installation ISO (called boot.iso) is available from the 5/os/<arch>/images/ directory on CentOS mirrors.

This latter mode of installation, however, is only really reliable via a LAN (an Intranet installation) and not via the Internet.

4. What kernels are available?

CentOS 5 provides the following kernel packages:

• kernel: Contains the 'normal' kernel. This kernel includes support for both UP and SMP machines.

• kernel-PAE (x86-only): Contains a kernel with support for 64GB of memory on x86 systems through Physical Address Extensions (PAE). Only x86 CPUs that support PAE can run this kernel. This kernel is provided because x86 systems can't address more than 4GB of memory without PAE extensions.

• kernel-xen: Contains a Linux kernel that runs on the Xen hypervisor, for both privileged (dom0) and unprivileged (domU) domains. The Xen kernel is compiled with PAE support.

Additional kernels that have some more options enabled are available through the CentOSPlus repository.

5. Bind is broken in CentOS 5

No, it's not. Yes, it looks like it, as bind-9.3.3 in CentOS doesn't install the config files anymore, at least not where you would expect them. That was a deliberate choice by our upstream vendor. See this bugzilla entry.

Basically you can just copy the example files from /usr/share/doc/bind-9.x.x/sample/etc/ and /usr/share/doc/bind-9.x.x/sample/var/ to start your own configuration from.

Or you can use system-config-bind to set things up.

Documentation on bind can be found in the Deployment Guide, see Chapter 16.

6. yum groupinstall "GNOME Desktop Environment" complains about a missing libgaim.so.0

This actually is a bug from our upstream provider, see this bugzilla entry.

You can work around that with yum --exclude=nautilus-sendto groupinstall "GNOME Desktop Environment".

This bug was fixed in CentOS 5.3.

7. How do I change my server's name

Running as root:

• hostname acme.dev.nul

(assuming you wish to name the host: 'acme.dev.nul'), and adding or editting the "HOSTNAME=" line in:

• /etc/sysconfig/network

appropriately will do the trick.

Some applications also want to be able to do a lookup of hostname to IP, and for that purpose, editting /etc/hosts is often done. Another and better solution to that second question is to place the server in an environment with a working forward and reverse DNS and letting the initscripts manage the matter. We just answer the question about changing a server's name here.

See also the file documentation concerning the initscripts, which in the first instance handle the setting of the server name based on the values found in /etc/sysconfig/network or /etc/sysconfig/network-scripts/ifcfg-ethX:

• rpm -ql initscripts | grep doc

8. How long will CentOS 5 be supported?

We intend to support CentOS 5 until Mar 31st, 2017 The current plan is this:

• Full Updates (including hardware updates): Currently to Q4, 2012

• Updates ( including minor hardware updates): Up to Q1 of 2014

• Maintenance Updates Q1, 2011 - Mar 31st, 2017

  Full Updates

  During the Full Updates phase, new hardware support will be provided at the discretion of CentOS via Update Sets. Additionally, all available and qualified errata will be provided via Update Sets (or individually {and immediately} for Security level errata.) Update Sets normally will be released 2-4 times per year, with new ISOs released as part of each Update Set. In the 5.x numbering scheme, the .x is the number of the Update Set.

  Maintenance Updates

  During the Maintenance updates phase, only Security errata and select mission critical bug fixes will be released. There will be few, if any, Update Sets released.

9. How do I disable IPv6?

• Edit /etc/sysconfig/network and set "NETWORKING_IPV6" to "no"
• For 5.4 and later, replace in /etc/modprobe.conf

alias ipv6 off

by

options ipv6 disable=1

Alternative (which might be easier and works on any release with /etc/modprobe.d):

# touch /etc/modprobe.d/disable-ipv6.conf
# echo "install ipv6 /bin/true" >> /etc/modprobe.d/disable-ipv6.conf 

• For CentOS 5.3 or older, add the following to /etc/modprobe.conf :

alias ipv6 off
alias net-pf-10 off

• Run /sbin/chkconfig ip6tables off to disable the IPv6 firewall

• Reboot the system

With the 5.4 update symbol/ipv6 module dependency capabilities have been introduced; therefore, if IPv6 has been previously disabled as above an upgrade to the bonding driver in 5.4 will result in the bonding kernel module failing to load. For the module to load properly use instead:

# touch /etc/modprobe.d/disable-ipv6.conf
# echo "options ipv6 disable=1" >> /etc/modprobe.d/disable-ipv6.conf 

Upstream employee Daniel Walsh recommends not disabling the ipv6 module but adding the following to /etc/sysctl.conf:

net.ipv6.conf.all.disable_ipv6 = 1

10. How do I install a software RAID on CentOS 5?

There are two kinds of RAID: hardware RAID and software RAID. The first thing that everyone needs to understand is that many of the new SATA RAID motherboards do not have real hardware RAID, but instead contain a software RAID. The hardware manufacturer provides a software driver to have Windows recognize this a RAID, however it is not hardware RAID, any more than winModems are full hardware modems. So, in these instances, software RAID on Linux can be used. Here is documentation on how to do software RAID on CentOS:

• Redundant Array of Independent Disks (RAID)

• mdadm guide (note: do not install mdadm from the tarball per the article, instead use the command: yum install mdadm, if required)

• mdadm on FedoraNews

• How to Setup a Software RAID on CentOS 5

Man pages: mdadm, mdadm.conf, md

After installation of a software RAID1, you must install GRUB on both partitions. Here are articles that address issues related to that:

• Are You Unable to Boot With Your RAID Card?

• GRUB on a mirrored boot partition

11. What is the root password of the CentOS 5 Live CD?

No password set for root (as of CentOS-5.1)

12. When will CentOS 5 for ''your favorite architecture'' be released ?

Now that CentOS 5.1 for i386 and x86_64 has been released the developers have indicated that this is the planned order of release of other architectures : ia64 (Itanium), ppc (PowerPC, POWER), sparc.

13. Is PHP 5.2.5 released for CentOS?

Short answer: No, but PHP 5.3 is.

A bit longer answer: No. As with each other program in CentOS, the version numbers of released software will not change over the life time of a CentOS product. CentOS 5.0 contained PHP 5.1.6, and that is the point version PHP will stay at for the life time of CentOS 5. On the other hand PHP 5.3.3 was officially included and is therefore supported in the distribution since minor release 5.6. The separate php53 package fills this task. Be sure to read the release notes before attempting to use it.

14. Where do I get the package signing key for CentOS 5?

You need to install the CentOS RPM signing key. It is not installed as part of the base system install for security reasons. This provides you the opportunity to validate the key before installing it on your system. RPM has the capacity to retrieve the key from a Centos Mirror:

rpm --import http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5

(as root) will install ('import') the CentOS 5 package signing key for RPM to use to confirm a validly signed package. Please note that it is safer to import the copy of the key from the install ISO media. It is in the root directory of each ISO, as RPM-GPG-KEY, and the same key is present on disc 1 as RPM-GPG-KEY-CentOS-5. The reason this is safer is that a CD is immutable media, and when you verify ISO MD5SUMs, you are implicitly also verifying the key. As a backstop, this key is as follows:

-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: GnuPG v1.2.6 (GNU/Linux)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=o/Mx
-----END PGP PUBLIC KEY BLOCK-----

If there is any question as to the validity of the key, please enquire; if a forged key is encountered, please send details, and return contact details to reach you to: security@centos.org

15. Why do I get "memory for crash kernel (0x0 to 0x0) notwithin permissible range"?

During the firstboot configuration phase you did not choose to reserve some RAM for the crash kernel. This message is informational only and can be safely ignored. If desired, you can configure some RAM for Kdump with 'system-config-kdump'.

16. Why do I get "you need kernel source files" when I already have the kernel-devel package?

There are two possible causes. First, make sure your kernel-devel matches your running kernel. Run:

uname -a ; rpm -qa kernel\* | sort

Second, make sure you installed kernel-devel of the correct type. For example, kernel-xen requires kernel-xen-devel and kernel-PAE needs kernel-PAE-devel.