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-   -   setting up new RH server, trouble figuring out partitions (naive about fdisk) (

eje4 07-27-2009 02:43 PM

setting up new RH server, trouble figuring out partitions (naive about fdisk)

We bought a new Dell server with RH Enterprse pre-installed. I naively expected that it would be set up with a partition configuration that would make use of the whole 750 GB disk. But no. It came with a minimal partition configuration that only actually uses a very small fraction of the total disk space, and the rest of the disk is unaccessible with the current partitions. I would naturally like to modify the partition setup so that we can use the entire disk. I'm a newcomer to this stuff and, although I've read the documentation on fdisk, I still can't get a handle on exactly what I need to do to accomplish this.

Here is our current situation: The output from fdisk -l shows this:

Disk /dev/sda: 750.1 GB, 750156374016 bytes
255 heads, 63 sectors/track, 91201 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sda1 1 8 64228+ de Dell Utility
/dev/sda2 9 661 5245222+ 8e Linux LVM
/dev/sda3 * 662 686 200812+ 83 Linux
/dev/sda4 687 91201 727061737+ 5 Extended
/dev/sda5 687 91201 727061706 8e Linux LVM

The output from df -h shows as follows:

Filesystem Size Used Avail Use% Mounted on
3.9G 661M 3.1G 18% /
3.9G 204M 3.5G 6% /home
3.9G 1021M 2.7G 28% /var
3.9G 137M 3.6G 4% /tmp
7.8G 3.9G 3.5G 53% /usr
/dev/sda3 190M 25M 156M 14% /boot
tmpfs 3.9G 0 3.9G 0% /dev/shm

The first thing that confuses me is that the /dev/ names in the second list don't correspond to the /dev names in the first list. Why is that? For example, just what is /dev/mapper/VolGroup00-LogVol00?

If anyone has any guidance for me on how I can get started setting up my partitions properly so I can make use of the entire disk, I'd appreciate hearing it.

Thanks very much,

neonsignal 07-27-2009 08:21 PM

Caveat - only having a desktop system not using LVM, I can't give you specific details here, but hopefully this will get you started.

Your system is set up with logical volumes, which is a layer on top of the old style of disk partitioning. The advantage of logical volumes is that volumes can be extended (even across multiple physical devices) and moved in ways that are not possible with hardwired partitions.

The output of df is confusing because you cannot see the connections between the logical volumes and the underlying partitions. Have a look at commands like 'lvdisplay -m' and the other lvm tools.

Looking at the output of fdisk, the whole disk has already been partitioned and formatted, but not all of the physical space has been allocated to filesystems. I don't know how to do this for LVM systems, though you will find documentation here.

On a server it makes sense to keep separate logical volumes for various purposes (whereas on a desktop the tendency is to preallocate all the spare space to /home). And because you can add logical extents to a logical volume without disruption, there is no need to allocate everything at the beginning.

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