Adding Additional Disk Drives to CentOS 5/6

Adding a new drive to CentOS or RedHat systems.

Making use of a second drive for extra space? Here's a quick run-down:

1) Make sure you know which disk is being formatted. First, second, and third drives will be /dev/sda, /dev/sdb, and /dev/sdc respectively. Check this with fdisk -l

[03:50:04] [[email protected] ~]# fdisk -l

Disk /dev/sda: 34.3 GB, 34359738368 bytes
255 heads, 63 sectors/track, 4177 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          13      104391   83  Linux
/dev/sda2              14        4177    33447330   8e  Linux LVM

Disk /dev/sdb: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/sdb doesn't contain a valid partition table

2) You can see that /dev/sdb (our second hard drive) does not have any partitions. We will need to create a partition(s) on the drive and then make a file system on it, then mount it. Let's write partitions to the drive using fdisk /dev/sdb:

[03:53:01] [[email protected] ~]# fdisk /dev/sdb
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel. Changes will remain in memory only,
until you decide to write them. After that, of course, the previous
content won't be recoverable.

Command (m for help): m
Command action
   a   toggle a bootable flag
   b   edit bsd disklabel
   c   toggle the dos compatibility flag
   d   delete a partition
   l   list known partition types
   m   print this menu
   n   add a new partition
   o   create a new empty DOS partition table
   p   print the partition table
   q   quit without saving changes
   s   create a new empty Sun disklabel
   t   change a partition's system id
   u   change display/entry units
   v   verify the partition table
   w   write table to disk and exit
   x   extra functionality (experts only)

Command (m for help):

3) As you can see from the help menu (by using the command "m") we want to add a new partition. Using the defaults will use the entire disk. After it's created, you will want to use the command "w" to "write table to disk and exit".

Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
Partition number (1-4): 1
First cylinder (1-1044, default 1): 1
Last cylinder or +size or +sizeM or +sizeK (1-1044, default 1044): 
Using default value 1044

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
[03:54:58] [[email protected] ~]# 

4) Now you will notice that the output of fdisk -l /dev/sdb shows a partition as /dev/sdb1:

[03:57:08] [[email protected] ~]# fdisk -l /dev/sdb

Disk /dev/sdb: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1        1044     8385898+  83  Linux

5) Now we need to create a file system on it. I've always used ext3 for general use/purposes. You'll want to use the command mkfs -t ext3 /dev/sdb1 as shown here:

[03:58:38] [[email protected] ~]# mkfs -t ext3 /dev/sdb1
mke2fs 1.39 (29-May-2006)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
1048576 inodes, 2096474 blocks
104823 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=2147483648
64 block groups
32768 blocks per group, 32768 fragments per group
16384 inodes per group
Superblock backups stored on blocks: 
	32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632

Writing inode tables: done                            
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 38 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.

6) Great, now we have a single partitioned secondary drive using ext3 file system. Now you want to create a directory to mount it in; lets just use "/drive2". You'll need to use the command mount -t [filesystem] [source] [mount directory] to mount it.

[03:59:50] [[email protected] ~]# mount -t ext3 /dev/sdb1 /drive2/

7) Now you'll notice, via df, that the drive is mounted:

[03:59:57] [[email protected] ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
                       28G  1.4G   25G   6% /
/dev/sda1              99M   19M   76M  20% /boot
tmpfs                1014M     0 1014M   0% /dev/shm
/dev/sdb1             7.9G  147M  7.4G   2% /drive2

8) Last step - you want to make sure the drive automatically mounts itself when the server boots/reboots. You'll need to add the following line to your /etc/fstab file:

/dev/sdb1  /drive2  ext3  defaults 0 0


All done!

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