[mythtv-users] OT: Second SATA on Promise 376 controller? (Happy holidays!)

Stroller Linux.Luser at myrealbox.com
Sun Dec 26 00:39:24 UTC 2004

On Dec 25, 2004, at 8:26 pm, GERALD SCHEPENS wrote:
> ...  I just want to add another couple hundred gigs without having to 
> totally reformat, etc.
> Also, can a person take a non-LVM'd drive such as mine is currently 
> and begin using LVM with it and another drive, again without wiping 
> the existing disk?

This is fairly straight-forward, at least once you've done it the first 
time. The important thing to remember is that a logical volume looks to 
the filesystem as just another partition - it can be resized easily & 
it can span more than one physical drive, but it can be referred to as 
/dev/volumes/something, in the same way that conventional partitions 
are referred to as /dev/hda1 &c.

I haven't started building a mythtv box, yet, but presumably you have 
all your films in a directory such as /var/mythtv/movies or 
/home/mythtv. If you don't already have this as a mount point for a 
partition then things are a bit more involved, so let's start by 
assuming everything you want on LVM is already in a separate partition 
which you can format after you've moved it:
- First, shutdown the PC, add the new hard-drive & restart.
- Next, initialise the new drive with `pvcreate`, create & activate 
your logical volume group, add the new drive to it and create & format 
a logical volume of a suitable size & filesystem, as shown at 
<http://www.tldp.org/HOWTO/LVM-HOWTO/>. Once you're familiar with the 
concepts of physical & logical extents, chapter 11 is all you'll ever 
need to refer to.
- You should now be able to mount the new volume, using something like 
`mount /dev/volumes/movies /mnt/temp`, so `cp -aRf 
/path/to/movie/directory/ /mnt/temp/`
- You'll probably need to shut-down MythTV before proceeding - I always 
go to a single-user runlevel - and backup & edit your /etc/fstab to 
mount the /dev/volumes/movies at /path/to/movie/directory/. You'll need 
to comment out the old entry for /path/to/movie/directory/ and specify 
the filesystem with which you formatted the new logical volume in the 
new fstab entry.
- Reboot & test.
- Provided everything has gone ok you can now add the old partition to 
the logical volume group using `pvcreate` & `vgextend`. Then enlarge 
the movies volume as described as 

It becomes a bit more of a pain if you've currently got /etc, /lib, 
/bin and suchlike in the same partition as your movies. If you have a 
partition that you'll want smaller, preserving the data, you'll have to 
copy everything off that partition, delete it, set up the new 
partition(s) / logical volumes and then copy the data into the new 
arrangement. I gather it's kinda tricky to get your root partition 
itself on LVM, so I keep /etc, /lib, /bin, /sbin and so on on a 
conventional partition of 6gig and then hive off only my interesting 
data onto logical partitions, although experts may tune finer than 

Worst case is that you currently have something like this in /etc/fstab:
   # <fs>                  <mountpoint>    <type>  <opts>          
   /dev/hda1               /boot           ext3    noauto,noatime        
   1 2
   /dev/hda3               /               reiserfs noatime              
   0 1
   /dev/hda2               none            swap    sw                    
   0 0

In this case, I'd advise booting from a liveCD to do the work - I use 
the Gentoo ones. I'd mirror everything over to the new hard-drive & use 
that as the new boot device - once that's working you can add the 
original drive back in as secondary & add it to the logical volumes.

So fit the new hard-drive as secondary & use `fdisk` or `cfdisk` to 
make a better partition layout. Don't worry about LVM just yet, just 
make a big separate partition for your movies at first. Something like 
100meg for /boot, 500 or 1024meg for swap, a few gig for system files 
like /etc & /lib & the rest for /path/to/movie/directory/. Mark the 
smallest directory as bootable & put filesystems on the partitions.

Once you've finished fdisking you'll probably need to reboot before you 
can access it the new partitions.
At the liveCD shell prompt:
   # mkdir /mnt/old /mnt/new
   # mkdirhier /mnt/old/boot /mnt/new/boot 
Mount the partions appropriately:
   # mount /dev/hda3 /mnt/old
   # mount /dev/hda1 /mnt/old/boot
   # mount /dev/hdb3 /mnt/new
   # mount /dev/hdb1 /mnt/new/boot
   # mount /dev/hdb4 /mnt/new/path/to/movie/directory
Copy the files across:
   # cp -Rfva /mnt/old /mnt/new
Reward yourself with a cup of tea and a cigarette whilst your drives 
crunch merrily. The next thing is to do stuff with grub to make the 
second drive bootable - I do this by removing the original hard-drive, 
setting the new one as master, booting from a LiveCD & chrooting in 
before running grub. The GRUB HOWTO is probably worth a look-see before 
you start. You'll also need to edit the new drive's fstab to mount the 
new /dev/hda4 as /path/to/movie/directory before you boot it. Once 
you've got the new drive booting & you're sure you're happy with it all 
working you can set the original drive as slave & go back to paragraph 

It's all a bit time-consuming, but as long as you're clear how it all 
works and you type carefully you'll be fine. When you've done this the 
once you'll be plenty confident about doing it another time. Feel free 
to post the output of your current `df -h` & ask for advice.


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