Add new partition to Centos hard drive

Question

My hard drive currently has (I believe) 2 partition; boot (sda1) and everything else (sda2?). Some of the hard drive is also being used as swap memory, but I don't really understand how that effects things. The server is physical and I have a LiveCD.

How do I add a new partition (1 MB, ext3) to the hard drive, and make sda2 smaller to accommodate the new partition?

Any additional comments on how lvm, /dev/mapper, and dm-0 and dm-1 apply would be appreciated, but not required.

Thank you

[root@desktop ~]# mount
/dev/mapper/vg_desktop-lv_root on / type ext4 (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
tmpfs on /dev/shm type tmpfs (rw,rootcontext="system_u:object_r:tmpfs_t:s0")
/dev/sda1 on /boot type ext4 (rw)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)
sunrpc on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw) 

[root@desktop ~]# fdisk -l /dev/sda

Disk /dev/sda: 1500.3 GB, 1500301910016 bytes
255 heads, 63 sectors/track, 182401 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x00056f9a

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          64      512000   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2              64      182402  1464625152   8e  Linux LVM

[root@desktop ~]# lvdisplay
  --- Logical volume ---
  LV Path                /dev/vg_desktop/lv_root
  LV Name                lv_root
  VG Name                vg_desktop
  LV UUID                DhBjdq-0UJR-dJjx-bgH6-adGJ-TL43-8DrZR7
  LV Write Access        read/write
  LV Creation host, time desktop.xxx.com, 2013-07-01 04:10:19 -0700
  LV Status              available
  # open                 1
  LV Size                1.36 TiB
  Current LE             356082
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     1024
  Block device           253:0

  --- Logical volume ---
  LV Path                /dev/vg_desktop/lv_swap
  LV Name                lv_swap
  VG Name                vg_desktop
  LV UUID                mNpyae-UtdA-MzJR-bbEc-D9OA-VPn8-ECMpbq
  LV Write Access        read/write
  LV Creation host, time desktop.xxx.com, 2013-07-01 04:13:25 -0700
  LV Status              available
  # open                 1
  LV Size                5.83 GiB
  Current LE             1492
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     1024
  Block device           253:1

[root@desktop mapper]# ls -l /dev/mapper
total 0
crw-rw----. 1 root root 10, 58 Jul  4 00:37 control
lrwxrwxrwx. 1 root root      7 Jul  4 00:37 vg_desktop-lv_root -> ../dm-0
lrwxrwxrwx. 1 root root      7 Jul  4 00:37 vg_desktop-lv_swap -> ../dm-1
[root@desktop mapper]#

Is this 1MB a requirement or just an example? The proper way is to shrink an LVM and add another one. — Nathan C, Jul 04 '13 at 14:16
@NathanC. I've since shrunk my LVM to 1000G. Question remains how do I add a new partition (using remaining space instead of only 1MB)? Thanks — user1032531, Jul 04 '13 at 15:21

score 2 · Accepted Answer · answered Jul 04 '13 at 15:26

2

You'll need to shrink your existing group with lvreduce to make room for the new volume. Then, you can use:

lvcreate -L 3G -n <lvname> vg_desktop where 3G is the size you want the volume to be. Then:

mkfs -t ext3 /dev/vg_desktop/<lvname> to format it. And finally, mount it with mount -t ext3 /dev/vg_desktop/<lvname> /mnt/somedir.

answered Jul 04 '13 at 15:26

Nathan C

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Thanks! Looks like I still have only (2) partitions (sda1 & 2), however, sda2 uses LVM to effectively have multiple partitions (in my new case, lv_root, lv_swap, and lv_myNewPartition). Correct? Also, I am sure you knew, but when mounting, I needed to add "lv_" to my selected . – user1032531 Jul 04 '13 at 15:47
That is correct. LVM is "logical" so it won't appear as an sda*-style partition. It's actually designed to span multiple drives too. – Nathan C Jul 04 '13 at 15:49
Makes sense. Do you know if LVM is slower than creating a new primary partition on a single drive? My reason for doing this is to store /var/lib/mysql on its own partition, see if ext3 is quicker, remove barriers, or whatever is needed. See http://serverfault.com/questions/518747/mysql-is-running-very-slow-on-centos-6x-not-5x for history. – user1032531 Jul 04 '13 at 16:04
LVM should be more or less the same. – Nathan C Jul 04 '13 at 17:32

Add new partition to Centos hard drive

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