OS upgrade

Sorry for my 2nd post in a day but I'm after some advice again.

I have a server with 8 disks. Disk 0 is not RAIDed the others are.
Disk is the system disk with /, swap, boot on. The OS is FC4.

The RAID partition uses LVM and is about 1.8Tb, 1TB in use.

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.

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.





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Re: OS upgrade

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.
>
>
>
>
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-admin" in
> the body of a message to majordomo@vger.kernel.org
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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.

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