Adding a new disk drive to Centos 6
Installing a new HDD in NON-HW RAID system using deprecated fdisk
NOTE: in current example we are using fdisk . you can create only up to 2TB partitions with fdisk. Nowadays you may use parted instead. Note that Your OS also should support GPT support in kernel in order to use partitions more than 2TB. So in this case we use parted and partitions less than 2 TBs. Also please note that in case you are using HW RAID you most likely should rather differ way to manage your partitions. In current case we suppose that there no hardware RAID controller present in a system . Also this way should be applied to the fully virtualized servers using KVM or XEN-fullHV virtualisation tech.
First of all take a look on all disks installed in your system to be sure you are not mix up anything:
lsblk -io KNAME,TYPE,SIZE,MODEL
The disk drives in Centos is named hd* or sd*. In system with only one HDD you should receive following output:
# ls /dev/sd* /dev/sda /dev/sda1 /dev/sda2
Now connect new HDD to the system. If it is visible to BIOS it will be automatically detected by OS.
After new HDD is installed output of the same system will be like this:
After new HDD is installed output of the same system will be like this:
# ls /dev/sd* /dev/sda /dev/sda1 /dev/sda2 /dev/sdb
Check once again with lsblk, you'll see the disk added:
lsblk -io KNAME,TYPE,SIZE,MODEL <----ommited---> sdb disk 1T WDC WD100XXXX-X
The new HDD is assigned sdb with no partitions. A new partitions can be created on the new HDD and then mounted or the disk can be added to an existing volume group as a physical volume.
Creating partitions
Creating partitions using fdisk utility (root rights required).
# fdisk /dev/sdb
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0xd1082b01.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.
Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)
WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
switch off the mode (command 'c') and change display units to
sectors (command 'u').
Command (m for help):
Switch off DOS compatible mode and change the units to sectors by entering the c and u commands:
Command (m for help): c DOS Compatibility flag is not set Command (m for help): u Changing display/entry units to sectors
In order to view the current partitions on the disk enter the p command:
Command (m for help): p Disk /dev/sdb: 34.4 GB, 34359738368 bytes 255 heads, 63 sectors/track, 4177 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xd1082b01 Device Boot Start End Blocks Id System
fdisk output shows that the disk has no partitions yet because it has not been used before. New partition can be created by entering n (for new partition) and p (for primary partition):
Command (m for help): n Command action e extended p primary partition (1-4) p Partition number (1-4):
Currently we plan to create only one partition - partition 1, so the first available sector will be beginning and the last one will be end. If you wish to create multiple partitions you can specify the size of each partition by sectors, bytes, kilobytes or megabytes.
Partition number (1-4): 1
First sector (2048-67108863, default 2048):
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-67108863, default 67108863):
Using default value 67108863
Now when partition is specified write it to disk by entering w:
Command (m for help): w The partition table has been altered! Calling ioctl() to re-read partition table. Syncing disks.
The new partition is now visible as /dev/sdb1:
# ls /dev/sd* /dev/sda /dev/sda1 /dev/sda2 /dev/sdb /dev/sdb1
The next step is to create file system on the new partition with mkfs.ext4 utility.
# /sbin/mkfs.ext4 -L /backup /dev/sdb1
mke2fs 1.41.12 (17-May-2010)
Filesystem label=/backup
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
2097152 inodes, 8388352 blocks
419417 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=4294967296
256 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
4096000, 7962624
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 36 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
Now when a file system on the new partition is created we need to mount it so that it is accessible. For example, let's create a directory /media which will be our mountpoint.
# mkdir /media
Mount file system:
# mount /dev/sdb1 /media
Running the mount command with no arguments shows us all currently mounted file systems (including our new file system):
# mount /dev/mapper/vg_CentOS6-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) /dev/sr0 on /media/CentOS_6.0 x86_64 Disc 1 type iso9660 (ro,nosuid,nodev,uhelper=udisks,uid=500,gid=500, iocharset=utf8,mode=0400,dmode=0500) /dev/sdb1 on /media type ext4 (rw)
In order to Centos automatically mount new file system at boot add it to /etc/fstab file. Below is shown fstab configured to automount /media at boot:
/dev/mapper/vg_centos6-lv_root / ext4 defaults 1 1 UUID=0d06ebad-ea73-48ad-a50a-1b3b8ef24491 /boot ext4 defaults 1 2 /dev/mapper/vg_centos6-lv_swap swap swap defaults 0 0 tmpfs /dev/shm tmpfs defaults 0 0 devpts /dev/pts devpts gid=5,mode=620 0 0 sysfs /sys sysfs defaults 0 0 proc /proc proc defaults 0 0 /dev/sdb1 /media ext4 defaults 1 2
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