How To Find Un Allocated Space On Linux

March 9, 2011 | By
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Using only fdisk, the "start" and "end" columns in your 'fdisk -l' output are the start and end cylinders. From the header of your 'fdisk -l' output, you can also see how many cylinders the disk has and how many bytes a cylinder represents.

fdisk -l /dev/cciss/c0d0

Disk /dev/cciss/c0d0: 72.8 GB, 72833679360 bytes
255 heads, 32 sectors/track, 17433 cylinders
Units = cylinders of 8160 * 512 = 4177920 bytes

Device Boot    Start       End    Blocks   Id  System
/dev/cciss/c0d0p1   *         1       100    407984   83  Linux
/dev/cciss/c0d0p2           101      1642   6291360   83  Linux
/dev/cciss/c0d0p3          1643      3184   6291360   83  Linux
/dev/cciss/c0d0p4          3185     17433  58135920    f  Win95 Ext'd (LBA)
/dev/cciss/c0d0p5          3185      4212   4194224   83  Linux
/dev/cciss/c0d0p6          4213      4983   3145664   83  Linux
/dev/cciss/c0d0p7          4984      5497   2097104   83  Linux
/dev/cciss/c0d0p8          5498      6011   2097104   82  Linux swap
/dev/cciss/c0d0p9          6012      9608  14675744   83  Linux

Since your last partition ends on cylinder 9608, you still have cylinders 9609 through 17433 unallocated. 7825 cylinders times 4 megs yields about 30g unallocated. This is approximate because your cylinders are actually just slightly under 4 megs (using powers of two), but I also rounded down on the final number, so it should be pretty close to the real number.

Or

Disk /dev/sda: 21.4 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 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         905     7164990   83  Linux
/dev/sda3             906        1036     1052257+  82  Linux swap / Solaris

Total space 21GB . You can use partx -l command to find the used space and can subtract from total space.

[root@localhost ~]# partx -l /dev/sda
# 1:        63-   208844 (   208782 sectors,    106 MB)
# 2:    208845- 14538824 ( 14329980 sectors,   7336 MB)
# 3:  14538825- 16643339 (  2104515 sectors,   1077 MB)
# 4:         0-       -1 (        0 sectors,      0 MB)

So my server has around 12 GB unallocated space.

Another option we have is to use parted command. You can use "free" parameter to get unallocated space and also disk partition. In my below examples, there is no partition on the hard disk and so it displays only free space.

[root@localhost ~]# parted /dev/sda print free
Model: ATA QEMU HARDDISK (scsi)
Disk /dev/sda: 2000GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:

Number   Start    End Size  File system   Name   Flags
17.4kB   2000GB   2000GB    Free Space

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Comments (2)

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  1. ronny says:

    thank you

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