Centos 4

The Computer Systems Lab is pleased to announce support for Centos 4 as a new desktop and server platform.

Centos is a rebuild of Red Hat Enterprise Edition 4. As such, it obtains many strengths from the corresponding Red Hat product, including highly tested and proven software component versions.

The information on this page should answer your questions about Centos. If you have questions that aren't answered here, please email lab lab@cs.wisc.edu and someone will assist you.

How Do I Schedule An Upgrade?

Point your web browser to https://www-auth.cs.wisc.edu, and click Continue to Web Forms. Then, under Account and Workstation Administration, click Request an Operating System upgrade. Fill in the information requested and click the submit button. One of the CSL staff members will contact you to confirm the upgrade time and coordinate any details regarding your upgrade.

What New Features Are Available?

Centos 4 includes the linux 2.6 kernel, which provides many improvements compared to kernel version 2.4 (the version included in Tao linux). Other major components include openafs 1.4, kde 3.3, gnome 2.8, X.Org 6.8.2, and others.

Centos uses the HAL (hardware abstraction layer) daemon to allow mounting and unmounting of usb-attached storage, as well as cd, dvd, and floppy disks (on computers equipped with suitable hardware). The CSL recommends the use of the kdf visual device manager for mounting and unmounting removable storage devices. However, the mount and umount commands can also be used to mount and unmount removable storage devices.

While the CSL doesn't support Gnome, we continue to take steps to provide a usable Gnome desktop for those individuals who prefer this environment. In this iteration of the desktop, we have returned to the native (RHEL) Gnome build. Although Ximian provided a highly functional desktop, we have concluded that using the native build will provide a more up-to-date and consistent Gnome desktop.

How Much Disk Space Will I Have?

The default Centos 4 install requires approximately 18 GBytes of disk space. With a 40 GByte disk, this would leave 22 GBytes in /scratch for local storage. Centos can be installed on disks as small as 20 GB.

This only affects local disk space in /scratch, and has no impact on your home directory or research project space in afs.

What Are The Differences In Available Software?

Wherever possible, all programs that were available on previous linux distributions will also be available for Centos 4. There are some situations where support has been dropped for a program either by Red Hat or by upstream maintainers. The CSL will deal with these on a case-by-case basis.

If you are unsure of whether or not a particular application is available for Centos 4, you can check for its availablity by logging in to our test system, cent40-test.cs.wisc.edu, and checking for yourself.

Release Notes

The following caveats exist with Centos 4. Workarounds are listed if known.

• Use /usr/bin/cdrecord to record all CD and DVD .iso images, as in: /usr/bin/cdrecord ISO_IMAGE . The only option that may need to be specified is -dao which may be required on some drives. You should not need device=, speed=, or other options. You can always use -v to show more information about the burn. Some individuals have reported failed burns when writing CDs/DVDs from .iso files in /afs. We strongly encourage copying .iso files to your CentOS computer's local disk and burning from there.

• A new version of groff has been installed, which outputs documents for screen viewing using different escape sequences. If a user has a PAGER environment variable set to use the less command, the PAGER options must include -r or -R to view the document correctly. This most often shows up with the man command.

• There is an afs issue of data appended to a file on one workstation not being immediately available on other workstations without a close()/open() or stat() of the file in question.

• Users of xscreensaver may need to edit or remove their ${HOME}/.xscreensaver file to avoid spurious messages at startup.

• /s/std/bin/gv no longer exists. Please use /s/std/bin/mgv instead.

• When moving files from local disk to afs, The message warning: security context not preserved `foo': Operation not supported may be displayed. This message is related to the selinux security subsystem present in the linux 2.6 kernel, and can be safely ignored.

• The sound subsystem on CentOS is initialized with the volume control set to zero. Use the alsamixer program to increase the volume to a comfortable level.

• The network packet sniffer formerly known as ethereal is now called wireshark. Run wireshark instead of ethereal. The command-line syntax is exactly the same.

What Versions Of Red Hat Software Will Be Installed?

To see the current software install set for Centos 4, please ssh to cent40-test.cs.wisc.edu and run the command:

rpm -qa

This will display the entire set of rpms included in the base install.

-- DavidThompson - 18 Jun 2007