[PLUG] Odd partition has appeared

John Jason Jordan johnxj at comcast.net
Sun Nov 7 19:12:40 UTC 2010


On Sun, 7 Nov 2010 08:17:56 -0800
Denis Heidtmann <denis.heidtmann at gmail.com> dijo:

>On Sat, Nov 6, 2010 at 11:02 PM, John Jason Jordan
><johnxj at comcast.net>wrote:

>> I just looked at the GUI again. It has a button for Expand Volume
>> Group, and a button for Remove Selected Physical Volume(s), but there
>> appears to be no way to shrink a volume with the GUI.

>Is there any chance that under "Expand Volume Group" you can
>"expand" by X >0.5, or minus 100 G, or some such?  It would not be the
>first time a title was less than accurate, e.g., the "Start" button.

It's considerably more complicated than that.

I have been googling and searching the Fedora forums. Most of what
Google turns up is in the Fedora forums, because apparently Fedora has
been in the cutting edge of implementing logical volume groups. There
are a lot of Fedora users trying to figure out how they work,
especially how to shrink one. The usual case is installing Fedora, then
later wanting to make a separate partition to install another OS into.

In addition to the Logical Volume Manager GUI that I found earlier, I
have discovered Palimpsest, which also comes with Fedora (in
Applications > System Tools > Disk Utility). It has more buttons, but
still no button for "shrink."

The process is not trivial. Apparently first you have to boot to Rescue
mode and make sure your root filesystem is not mounted. Right there I
am confused, because how can you boot without mounting and reading
the root filesystem? Then you use commands like lvm --pvresize and lvm
--lvresize, neither of which I understand. Another part of the problem
is that a default installation of Fedora does not create a separate
swap partition; instead swap is allocated somehow at the end of the
root partition. And the pvresize and lvresize cannot yet resize the root
partition when the swap is there, so the swap has to be moved out of
the way and then put back afterward. Or something like that. It's still
all very fuzzy to me.

I do suggest for anyone considering installing Fedora that you not
let Fedora use its default partition scheme:

1) Make the boot partition at least 1 GB for future needs. Current
    versions of Fedora set it to 500 MB, but I think that is still
    shortsighted.
2) Make your root filesystem (and /home if you want it on a separate
    partition) less than the remaining space on the disk so you won't
    have to shrink it later.
3) Volume groups can include multiple partitions which the OS sees as
    one disk. So split your disk into multiple smaller partitions and
    let Fedora stripe them into one volume group. Removing a
    partition from a volume group is trivial compared to having to
    shrink a partition.

I'll keep reading and perhaps eventually I'll get it all figured out.
Unfortunately, I'm starting from zero, because I don't understand what
terms mean like "extent" and "sector," among many others.

Even though I don't understand it all yet, the best Fedora post I have
found so far is:

http://fedorasolved.org/Members/zcat/shrink-lvm-for-new-partition



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