RHEL4  to RHEL5 upgrade

mokkan
mokkan used Ask the Experts™
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We would like to upgrade few critical boxes to  RHEL4 to RHEL5 and gathering some information. I read few articles and people are recommending  to install  RHEL5, and then restore the data. Some of the library functions are not working properly when they upgrade? Is it right? I need some confirmation. Thanks in advance.

 
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RedHat strongly recommends to do a fresh installation. If you still want to Upgrade Make a full backup. Boot from RHEL5 media and tell installer that you want to upgrade existing system.
Since it is a major upgrade, you may want to go to RHEL 6 instead or Scientific Linux 6 (free clone or RHEL6).

RHEL4 and RHEL5 are fundamentally different systems, like the way RHEL4 was different from RHEL3.  It is not a good idea to try to upgrade it when base packages are totally different.

Author

Commented:
Thank you for your comments.

When you restore, do we only need to restore? Home directory? When it comes to  backup and restore, there will be lots of issues. Some of the applications are using  using  lots /etc/xxxx .conf file etc...

What are the files we need to backup? I know it is depends on the system, but gen really for RHEL4 upgrade what are the filesystems need to backup?
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Backup everything on users home directories. i.e.

/home

OS configuration is generally under /etc so backup /etc.

/etc


Logs will be under

/var/log

PS: You may have to customize based on your installation

Commented:
Apart from the sreedhar2u suggest, take backup of the data of any application which you are running. Take backup of the database any, if you are running.

The bottom of the line is take full backup of your system.

I would suggest you a very good way.

Instead of installing RHEL5 or 6 on the same machine, use a different machine for the same and restore your data then run and test your application. If you get stuck anywhere then you can immediately swith to your old setup.

Author

Commented:
Thank you for all of your inputs. When I restore, can I overwrite all the /etc/ configuration files by  RHEl4 from back, once I have upgraded?
Commented:
No you are not supposse to do that, Lost of earlier configuration may not supprt your system and It may get crash. You should modify the files accordingly.

Author

Commented:
Thank you for your comments. How do I know what are the files can be overwritten? And what are the files I need to keep? That's the problem.

Author

Commented:
I couldn't find release lots of release5, do you have the link? I have it for rhel6.
CentOS 5 (Red Hat clone for RHEL5)
http://www.centos.org/modules/tinycontent/index.php?id=15

Scientific 6 (Red Hat clone for RHEL6)
http://www.scientificlinux.org/

Redhat is controlled.  You have to pay for it to get it from their channels.

Author

Commented:
How do I know what are the files can be overwritten? And what are the files I need to keep? That's the problem.
Commented:
I am not getting you, are you going to perform a upgrade or doing a fresh install.
You need to install a fresh server.  You need to make a backup of your configuration files and the user files.  You also would need your portions of some system kind of files like /etc/passwd --list of users, /etc/shadow --password hashes, /etc/group --user groups, networking files -- to setup networking configuration, likewise files for each service like httpd.conf if you are running apache, etc.

You will also need personal accounts to be backed up because they are not version dependent.

Author

Commented:
Thank you guys.

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