This article is a HOWTO for adding a new drive in
Linux.
Adding New Drives
There are many reasons why you would need to add a new
drive to your Linux box. You might have out-grown your
current space limitations, or you may want to add a
separate drive for a specific project or service. In
any case, if you follow this guide, you should have no
problems. First, you must be familiar with the naming
scheme Linux uses for your drives. For purposes if
this article, everything highlighted in blue is the
command you must type at the terminal prompt. Anything
highlighted in red indicates changes made by a
previous command or something you should pay special
attention to. Anything highlighted in green is simply
the standard output from a terminal or issued command.
The machine used for this guide is running Red Hat
Enterprise Linux.
Conventional Naming
This article assumes you know the difference between
primary, extended and logical partitions. In the
following example, I added a SCSI hard drive with one
primary partition. With that being said, I'll continue
explaining the naming scheme. Linux gives each drive a
3 letter name followed by a partition number. If you
are using IDE drives, these will all be named hd**.
Where hd denotes the drive and the next two variables
are associated with IDE order (primary master,
primary slave, etc) and partition number. So, your
primary master drive will always be named hda. If you
are using SCSI drives, everything remains the same
except instead of using hd, drives are named sd**.
Your SCSI primary master drive will always be named
sda. All of these devices reside under the /dev
portion of your Linux file system. For instance, as
root, you can issue the following command to view the
naming combinations possible for your system.
Remember, in this example, I am using SCSI hardware.
If you are using IDE, simply use hd is place of sd
here.
[root@roswell root]# ls /dev/sda*
/dev/sda /dev/sdab10 /dev/sdad12 /dev/sdaf14
/dev/sdah2 /dev/sdaj4 /dev/sdal6
/dev/sda1 /dev/sdab11 /dev/sdad13 /dev/sdaf15
/dev/sdah3 /dev/sdaj5 /dev/sdal7
/dev/sda10 /dev/sdab12 /dev/sdad14 /dev/sdaf2
/dev/sdah4 /dev/sdaj6 /dev/sdal8
/dev/sda11 /dev/sdab13 /dev/sdad15 /dev/sdaf3
/dev/sdah5 /dev/sdaj7 /dev/sdal9
/dev/sda12 /dev/sdab14 /dev/sdad2 /dev/sdaf4
/dev/sdah6 /dev/sdaj8 /dev/sdam
/dev/sda13 /dev/sdab15 /dev/sdad3 /dev/sdaf5
/dev/sdah7 /dev/sdaj9 /dev/sdam1
/dev/sda14 /dev/sdab2 /dev/sdad4 /dev/sdaf6
/dev/sdah8 /dev/sdak /dev/sdam10
----
Some results omitted**
----
[root@roswell root]#
Note that I omitted a large portion of the results
because they were huge! Remember that this list is not
dependent on the current number of hard drives in the
system, but the maximum naming possibilities for any
number of drives and partitions. Do not be surprised
if your results are rather lengthy as well.
Creating, Mounting, and Configuration New Partitions
Before adding an extra drive, this machine had 2
physical drives. Both of them were named accordingly
(sda and sdb) before the new drive was added. The
second drive containing the swap partitions was
automatically renamed when the new drive was added.
Notice the command and output below:
[root@roswell root]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 8.3G 2.4G 5.5G 30% /
/dev/sda2 99M 26M 69M 27% /boot
/dev/sdc1 16G 13G 2.3G 85% /export
<-- old sdb renamed to sdc by the Linux
none 250M 0 250M 0% /dev/shm
[root@roswell root]#
This command simply lists all currently mounted
drives, their names, and space usage. Notice that sdb
is not presently mounted. However, we know that it
exists otherwise, there would not be an sdc present. I
could not add my new drive as sdc because my SCSI
hotswap drive cage reserves the first two slots for
1.5" drives. So I was forced to make the new drive sdb
because it is a 1.5" drive.
Setting Partitions
You should be fairly familiar with fdisk. The commands
are somewhat different than it's DOS equivalent. See
the following commands and output:
[root@roswell root]# fdisk /dev/sdb
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):
If there is a problem, and there is no drive
associated with /dev/sdb, you will get an error
message. Remember, that nothing will actually be
executed until you issue a w command. It's always a
good idea to read through the variables of your
commands. Doing so will ensure that you aren't
forgetting anything. Let's get started!
Command (m for help): p
Disk /dev/sdb: 50.0 GB, 50019202560 bytes
255 heads, 63 sectors/track, 6081 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id
System
Command (m for help):
If you issue a p command, you will see any partitions
that currently exist on the drive. You can see by the
output above there are no existing partitions. This
drive is un-partitioned and unformatted. To create a
new partition, is the n command.
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-6081, default 1): 1
Last cylinder or +size or +sizeM or +sizeK (1-6081,
default 6081): 6081
Command (m for help):
In the output above notice that interval I selected
for the cylinders. Using the entire range allows you
create one partition across the entire drive. So, in
order to create a primary partition on /dev/sdb/ we
issued the following commands:
* n
* (creates a new partition) p
* (creates a primary partition) 1
(the number 1 denotes the partition will be
/dev/sdb1)
We can check the partition specifications we just
entered by using the p command again.
Command (m for help): p
Disk /dev/sdb: 50.0 GB, 50019202560 bytes
255 heads, 63 sectors/track, 6081 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id
System
/dev/sdb1 1 6081 48845601 83
Linux
Command (m for help):
Notice the new partition (highlighted in red).
However, we must issue a w command to finalize it. If
you messed anything up, you can use the d command and
specify which partition you want to delete.
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
[root@roswell root]#
Formatting
Now that the partition has been created, you need to
format the drive. You can format it with almost any
file system you wish. However, the most common Linux
formats are ext2 and ext3. Ext3 is simply a candy
coated version of ext2 that adds a logging feature.
You must specify which partition to format by calling
the device and partition number like this:
[root@roswell root]# mkfs -t ext3 /dev/sdb1
mke2fs 1.32 (09-Nov-2002)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
6111232 inodes, 12211400 blocks
610570 blocks (5.00%) reserved for the super user
First data block=0
373 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, 2654208,
4096000, 7962624, 11239424
Writing inode tables: done
Creating journal (8192 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.
[root@roswell root]#
What did we do there? Using the mkfs (make file
system) command, we specified the type (using the -t)
ext3 using the device and partition name (/dev/sdb1).
You have successful partitioned and formatted your
new drive. Wait, you're not done yet. You will want to
mount this partition to make it usable. You will also
want this partition to mount automatically when you
reboot the machine.
Mounting
In order to automatically mount a partition, you must
edit the /etc/fstab file. The fstab file tells Linux
where to mount all partitions located within the
system. The output below shows the current fstab file
before including the newly added drive:
[root@roswell root]# vi /etc/fstab
LABEL=/ / ext3
defaults 1 1
LABEL=/boot /boot ext3
defaults 1 2
none /dev/pts devpts
gid=5,mode=620 0 0
LABEL=/export /export ext3
defaults 1 2
none /proc proc
defaults 0 0
none /dev/shm tmpfs
defaults 0 0
/dev/sdb2 swap swap
defaults 0 0
/dev/cdrom /mnt/cdrom
udf,iso9660 noauto,owner,kudzu,ro 0 0
/dev/fd0 /mnt/floppy auto
noauto,owner,kudzu 0 0
You may notice I viewed this file using vi. Vi is a
simple text editor that may or may not be loaded on
your Linux system. It is somewhat similar to emacs. In
any case, both programs can perform the same task. We
will mount the new partition as /media. Remember to
create a directory named media, otherwise fstab won't
be able to mount the partition. It is shown
high-lighted red in the output below:
LABEL=/ / ext3
defaults 1 1
LABEL=/boot /boot ext3
defaults 1 2
none /dev/pts devpts
gid=5,mode=620 0 0
LABEL=/export /export ext3
defaults 1 2
none /proc proc
defaults 0 0
none /dev/shm tmpfs
defaults 0 0
/dev/sdb1 /media ext3
defaults 1 2
/dev/sdb2 swap swap
defaults 0 0
/dev/cdrom /mnt/cdrom
udf,iso9660 noauto,owner,kudzu,ro 0 0
/dev/fd0 /mnt/floppy auto
noauto,owner,kudzu 0 0
Next, issue a simple mount command providing the
partition name:
[root@roswell export]# mount /dev/sdb1
[root@roswell export]#
You're all done! You will be able to access the /media
folder immediately and after the machine reboots as
fstab will automatically re-mount it for you. If you
want to verify the partition is successfully present
and mounted, use the following commands:
[root@roswell media]# mount
/dev/sda1 on / type ext3 (rw)
none on /proc type proc (rw)
none on /dev/pts type devpts (rw,gid=5,mode=620)
usbdevfs on /proc/bus/usb type usbdevfs (rw)
/dev/sda2 on /boot type ext3 (rw)
/dev/sdc1 on /export type ext3 (rw)
none on /dev/shm type tmpfs (rw)
/dev/sdb1 on /media type ext3 (rw)
[root@roswell media]#
The red line shows our new drive freshly mounted. You
can check the space usage if you issue the following
command.
[root@roswell media]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 8.3G 2.4G 5.5G 30% /
/dev/sda2 99M 26M 69M 27% /boot
/dev/sdc1 16G 13G 2.3G 85% /export
none 250M 0 250M 0% /dev/shm
/dev/sdb1 46G 33M 44G 1% /media
[root@roswell media]#