Centos 3.4 --> Centos 4 ?

This really isn't even worth doing at this point since you can't use selinux with cPanel.

 

Use at your own risk, and YMMV!

# rpm --import http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-4
# rpm -Uvh ftp://sunsite.utk.edu/pub/linux/caos/centos/4.0/os/i386/CentOS/RPMS/centos-release-4-0.1.i386.rpm
# yum install glibc glibc-common
# yum install {kernel|kernel-smp} *(if this give you errors installing lvm2 read the note at the end of the post)
# rpm -e kernel-smp-2.4.21-27.0.2.EL (the release number may vary depending on your system)
# yum upgrade

conflict between udev and kernel

# rpm -qa|grep kernel
# rpm -e kernel-2.4-whatever

Also remember before rebooting to view the new kernel's initrd image size and generate a new one to compare.

# ls -l initrd-2.6.9-5.0.3.ELsmp.img
-rw-r--r-- 1 root root 195325 Mar 2 16:09 initrd-2.6.9-5.0.3.ELsmp.img

# mkinitrd initrd-2.6.9-5.0.3.ELsmp.img.new 2.6.9-5.0.3.ELsmp

# ls -l initrd-2.6.9-5.0.3.ELsmp.img.new
-rw-r--r-- 1 root root 474840 Mar 3 11:39 initrd-2.6.9-5.0.3.ELsmp.img.new

If this differs in size, like mines, move the old image to a different file name and cut off the '.new' extension in the new one's filename

# mv initrd-2.6.9-5.0.3.ELsmp.img initrd-2.6.9-5.0.3.ELsmp.img.dist
# mv initrd-2.6.9-5.0.3.ELsmp.img.new initrd-2.6.9-5.0.3.ELsmp.img

You need this in order to permit grub loading the new initrd (or change the grub.conf to point to the new generated initrd image, make your choice).

As you see the rpm generated initrd is smaller than the manually generated, which means there's something wrong in the rpm postinstall script. Make sure of this and take a lot of care before rebooting (otherwise be ready with a rescue CD to boot and follow the above procedure).

P.S.: you may have need of cutting the "smp" letters in the kernel name, depending on your hardware configuration.

I forgot to mention some important changes between 3.4 and 4.0 release. One of most important is the name changing of some packages, like rpmdb. On CentOS 3.4 that package has the name "rpmdb-redhat" while in 4.0 it has "rpmdb-CentOS". There's now way to upgrade it since it's a totally different name and the package install paths are different by the old one.

Just install the new rpmdb-CentOS through Yum or simply downloading it and installing with rpm -ivh, then remove with rpm -e the old rpmdb-redhat.

*NOTE: Possible errors installing lvm2 package
==============================
Yum may give errors trying to install the lvm2 package, since lvm1 is already installed and files may go to be conflicting (I had this issue only on two systems, the third worked perfectly, don't ask me why). The only solution I found is to manually install the downloaded rpms located in the /var/cache/yum/base/packages directory, just remember to use the --replacefiles switch to install lvm2, and later erase lvm1, like described below:

# cd /var/cache/yum/base/packages
# rpm -Uvh --replacefiles lvm2*.rpm (and some dependencies must follow)

 

Please keep in mind that it is very easy to make your system unbootable if you do not follow these instructions exactly or forget to do something mentioned.

Also, if the system is rebooted at any point during this process, you will find yourself with an unbootable system.

After everything is done, you will need to reboot in order to complete the upgrade.

 

Yes, we've done it several times with success.

After doing everything and rebooting, make sure you run

# /scripts/upcp --force

To make sure Cpanel is good to go.

You may also have to download and run

# sh buildapache.sea

because the upgrade sometimes makes Apache unusable.

 

I'd strongly suggest you read the information and FAQ on the CentOS site:
http://www.centos.org/modules/smartfaq/faq.php?faqid=27

As Webjunkie said, you risk making your server unbootable, so I'd suggest you only do it on a server you can afford to have to lose any data on and have an OS restore done on. It would seem much more secure to backup, load CentOS4 then reload, but each to their own

 

Ramsy - how long did the upgrade take you and on what spec machine?

If I'm ever going to consider a live upgrade it would be good to know how long things are likely to take.

 

You're in uncharted territory. If you don't know what to do, you should probably have waited for others to clear the way first. Good luck, though.

 

CentOS support is that way ---> www.centos.org

 

I highly suggest that you use rack911.com for this. Their pricing is $50 a box and their upgrade is flawless (even on my screwed over box) . They upgrade it in stages and get the main stuff out of the way and then they do the upgrade. As i said before. Flawless.

I just did an upgrade before from 3.5 - 4 and it worked flawlessly. However, DO NOT UPGRADE TO 4.1, as i do not know if cPanel works on it yet (and im not game to test it). One of the major changes between 3 and 4 is the change from 'devfs' to udev as devfs was obsoleted by udev. And if you do try to migrate to 4 and realise you fucked it over, dont try 'downgrading' to 3 by installing all the 3.x rpms again. It wont work.

Regards,
Brent

 

cPanel will work with 4.1, 4.1 is only a respin of all the updates in 4.0 up to where RHEL released v4 U1.

 

There seems to be a fair amount of interest in upgrading CentOS 3.4/3.5 to 4.0/4.1.

Can anyone explain what the benefits of doing so are? Are there any real noticeable benefits aside from the "it's newer, it must be better" line of thought?

 

I'm using Centos 4.1 at one of my box without a problem

 

I'm not so sure about this, I asked rack911 to migrate my RHE 3 to Centos 3.4 about a month ago. They answered very fast and I sent them my login details. As agreed, they started with the migration but they told me, that there is a problem with the kernel, so I'm using now Centos 3.4 with the RHE kernel. They promissed me to fix this later, but since there, I'm not able to get any status from them. I sent email, replyed to the ticket in their helpdesk system, but no answer anymore.

How do you comunicate with them?

Michael