[CentOS] Managing users and passwords

Thu Mar 24 12:17:09 UTC 2011
Kevin Thorpe <kevin at pibenchmark.com>

On 24/03/2011 03:45, Todd Cary wrote:
> I plan to make my current Centos 4 HD a slave and install Centos
> 5.5 on a new HD (master).  Then comes the challenge of of moving
> all of my /home/"user" data to the new master.  I have some
> preliminary questions:
>
> Is this a good strategy for installing Centos 5.5: keep the
> Centos 4 on a slave disk?
>
> Will the Centos 5.5 detect the slave disk (Centos 4)?
>
> Is there a way to move the users, groups and passwords from one
> disk to the new Centos 5.5?
>
> IT departments must have servers go down or want to install a new
> version of Linux and have the same challenges.
Starting with a new disk and making the old one a slave is a very good idea.
That's exactly what I'd do in your situation. Even better if you mount the
partitions on the slave as read-only then you know you have a fall-back
position.

Start with your new install and get all the packages installed that you 
need.
Now, assuming you aren't using anything clever for user logins you can 
splice
the users part of /etc/passwd /etc/shadow and /etc/group on to the system
parts of the new install. Don't overwrite the systems stuff as they may have
changed between versions. Then copy over /home using rsync or similar - if
you had this as a separate drive like I do then simply re-mount it. Make 
sure
the user and group permissions look right - if you spliced passwd  and group
properly then they'll be fine. Lastly you need to go through the servers 
and
services you need running and sort out the /etc directory entries for them.
Don't be tempted to just copy the old files over - it works most of the time
but you'll get bitten if the format of the file has changed.