15 managing disks - creating partitions fdisk /proc/partitions /dev/sda

By OK -

[svn@svn ~]$ cat /proc/partitions
major minor  #blocks  name

    8        0   31457280 sda
   8        1    1048576 sda1
   8        2   19921920 sda2
   8       16    5242880 sdb
  11        0    8086528 sr0
 253        0   17821696 dm-0
 253        1    2097152 dm-1
[svn@svn ~]$

sdb - new disk, there are no partitions on this disk


[root@svn ~]# fdisk /dev/sdb
Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Device does not contain a recognized partition table
Building a new DOS disklabel with disk identifier 0xf12de6be.

Command (m for help): 

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
   g   create a new empty GPT partition table
   G   create an IRIX (SGI) partition table
   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): p

Disk /dev/sdb: 5368 MB, 5368709120 bytes, 10485760 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0xf12de6be

   Device Boot      Start         End      Blocks   Id  System

Command (m for help): 

every sector is 512 bytes

sectors are default allocation unit which is used when creating partitions on disk


Let's add new partition. We should use primary partition unless we create more than 4 partitions on a disk


Command (m for help): n
Partition type:
   p   primary (0 primary, 0 extended, 4 free)
   e   extended
Select (default p): 
Using default response p
Partition number (1-4, default 1): 
First sector (2048-10485759, default 2048): 
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-10485759, default 10485759): +100M
Partition 1 of type Linux and of size 100 MiB is set

Command (m for help): p

Disk /dev/sdb: 5368 MB, 5368709120 bytes, 10485760 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0xf12de6be

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048      206847      102400   83  Linux

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

Calling ioctl() to re-read partition table.
Syncing disks.

[root@svn ~]# cat /proc/partitions 
major minor  #blocks  name

   8        0   31457280 sda
   8        1    1048576 sda1
   8        2   19921920 sda2
   8       16    5242880 sdb
   8       17     102400 sdb1
  11        0    8086528 sr0
 253        0   17821696 dm-0
 253        1    2097152 dm-1
[root@svn ~]# 

For error "device is busy" the best thing to do is reboot.

After we created partition, we can create file system on it


[root@svn ~]# fdisk -l

 Disk /dev/sda: 32.2 GB, 32212254720 bytes, 62914560 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x000c81c3

    Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     2099199     1048576   83  Linux
/dev/sda2         2099200    41943039    19921920   8e  Linux LVM

 Disk /dev/sdb: 5368 MB, 5368709120 bytes, 10485760 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0xf12de6be

    Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048      206847      102400   83  Linux

 Disk /dev/mapper/cl-root: 18.2 GB, 18249416704 bytes, 35643392 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/mapper/cl-swap: 2147 MB, 2147483648 bytes, 4194304 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

 [root@svn ~]# 

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