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fdisk

View and edit partition tables and disk parameters.

Mnemonic: Format disk.

util-linux package.

REPL interface. Non-interactive usage only with pipes... http://superuser.com/questions/332252/creating-and-formating-a-partition-using-a-bash-script

Does not create filesystems. For that see: mke2fs for ext systems.

Better use gparted for simple operations if you have X11

To view/edit partitions with interactive CLI prompt interface.

l

Show lots of partition and disk data on all disks:

sudo fdisk -l

Sample output for each disk:

Disk /dev/sda: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x7ddcbf7d

Device Boot   Start     End   Blocks  Id System
/dev/sda1  *    2048   3074047   1536000  7 HPFS/NTFS/exFAT
/dev/sda2     3074048  198504152  97715052+  7 HPFS/NTFS/exFAT
/dev/sda3    948099072  976771071  14336000  7 HPFS/NTFS/exFAT
/dev/sda4    198504446  948099071  374797313  5 Extended
Partition 4 does not start on physical sector boundary.
/dev/sda5    198504448  907638783  354567168  83 Linux
/dev/sda6    940277760  948099071   3910656  82 Linux swap / Solaris
/dev/sda7    907640832  940267519  16313344  83 Linux

TODO: what is the boot column?

REPL

Edit partitions for sdb on REPL interface:

sudo fdisk /dev/sdb

Operation: make a list of changes to be made, then write them all to disk and exit with w (write).

Most useful commands:

  • m: list options
  • p: print info on partition, same as using -l option
  • o: create new DOS partition table
  • n: create new partition
  • d: delete a partition
  • w: write enqueued changes and exit

Erase everything and create a single partition

printf 'o\nn\np\n1\n\n\nw\n' | sudo fdisk /dev/sdX

This does not create a filesystem, only the partition.

The one partition takes up almost the entire disk, except the first 2048 bytes which are reserved for the partition table.

TODO: why does it leave 2048 and not just 512 which is what the MBR needs?

You will now likely want to use mke2fs to create a partition like:

sudo mkfs.ext4 /dev/sdX1

Minimal size for a partition

Why fails for small images?

TODO http://superuser.com/questions/972433/why-does-fdisk-fail-to-create-a-new-partition-with-you-must-set-cylinders-if