Re: OS upgrade

My reasoning for saying that LVM uses files on the system disk was 
not just the lvmtab which on Fedora4 is /etc/lvm and it's files 
(lvm.conf) but also the /dev/ mappings, EG:

/dev/mapper/my_vol-scanning1
                       1.8T   718G   926G  44% /data

I was concerned about the recreation of the /dev files.

As it turned out, the CentOS set-up (Anaconda) detected the volume 
but it complained about /dev/sdb which is odd as I don't have one:

/dev/sda2               13G   5.1G   6.5G  44% /
/dev/sda1              136M    23M   106M  18% /boot
/dev/shm               1.1G      0   1.1G   0% /dev/shm
/dev/sda5              130G   1.1G   122G   1% /var

It didn't offer me the option of installing on the 137GB disk that is 
the un-RAIDed system disk, least don't remember seeing it. 

I wasn't confident enough to proceed so I rebooted to get a better 
idea of existing disk arrangements. That lead to an fsck, at which 
point I decided to call it a night as I did want to wait 2+ hours for 
it to check the 1.8TB and then start the upgrade.

I'll have to try and find a longer window to do this in. I am not 
sure about backing it up to a removable drive. I know it takes 4 LTO2 
tapes and most of the weekend to back up the system. A restore would 
take about the same.

I'll do an update around Easter I guess. Thanx for the responses.
Dermot.


On 14 Feb 2008 at 9:05, Adam T. Bowen wrote:

> Hi,
> 
> I'm no expert on this subject, but seeing as nobody else has replied 
> yet, I thought I would have a guess as to how this would work.
> 
> Beginner wrote:
> > I want to upgrade, or re-install with CentOS and I don't want to have 
> > to re-store all data on the RAID 5 volume but I am not sure that I 
> > can because the LVM will use files from the system disk.
> 
> Will it?  We used to use LVM on HPUX and although there was an 
> /etc/lvmtab file (think fstab), you could re-create it easily enough by 
> running the lvscan command.  This same command exists on Linux (although 
> there is no lvmtab), and according to the man page it runs 
> automatically.  There is also a --mknodes switch which is nice.
> 
> If you want to be sure that you can just slap a new OS on and it will 
> automatically scan for and set up your logical volumes, try booting from 
> a live Linux CD (Knoppix for example) and see if you can still see your 
> logical volumes.
> 
> Cheers
> 
> Adam
> 
> > Am I going to be able to maintain my existing LVM volumes during the 
> > re-install? Is there a procedure to maintain LVM or store in after an 
> > install or upgrade?
> > 
> > The system is backed but if I have to re-create the partitions and 
> > restore it will be off-line for several days and I would need to 
> > schedule it for a public holiday.
> > 
> > Any advice. Thanx,
> > Dp.