I have been looking but neither Gparted nor KDE Partition Manager can handle LVM. Working with the command line is probably fine but it would be clearer to have a GUI tool here. Does such thing exist?
Partition manager that can handle LVM
lvmpartition
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Your information is contradictory. /dev/md0 cannot simultaneously be a PV and have a partition table. file would recognize a PV. It seems that md0 is partitioned so that the LVM volume is rather /dev/md0p1 or /dev/md0p2.
Maybe for some reason pvscan / vgscan ignore /dev/md0 / /dev/md0p1 (and thus LVM cannot find the UUID). You may run pvscan through strace in order to check which block devices are scanned:
strace -e trace=open pvscan 2>&1 | grep /dev/md
The resize2fs does not support shrinking of a mounted file system:
DESCRIPTION The resize2fs program will resize ext2, ext3, or ext4 file systems. It can be used to enlarge or shrink an unmounted file system located on device. If the filesystem is mounted, it can be used to expand the size of the mounted filesystem, assuming the kernel and the file system supports on-line resizing.
As you are using fedora distribution, it's much easier to use System Storage Manager to change the size of your file system as it takes care on underlying partition/logical volume size change in one shot. Though you would need to boot the system off the one of LiveCD spins, provided by Fedora community (I recommend XFCE or LXDE to reduce the download size a bit), so in the terminal window just issue:
sudo ssm resize -s -5G /dev/mapper/pc_rperez_lvm-root
to decrease the root fs by 5 gigabytes, or
sudo ssm resize -s 15G /dev/mapper/pc_rperez_lvm-root
To set the fs size to 15 gigabytes.
If the ssm is not available in the live CD you would download, then do
sudo yum install system-storage-manager
prior to re-sizing.
to extend a volume to the maximum available space just omit the -s option:
sudo ssm resize /dev/mapper/pc_rperez_lvm-home
Best Answer
In RedHat's set of administration tools, there's system-config-lvm, which is optionally installable in other distributions like Fedora and Debian.
Recent versions of gnome-disk-utility support LVM.
The newly-released KDE 4.6 gains udisks as a Solid backend, which should provide LVM support. (Out of the three, this is the only one I haven't tried.)