Determine the size of a block device

Question

How can I find out the size of a block device, such as /dev/sda? Running ls -l gives no useful information.

Answer 1

How about:

fdisk -l

This will give you a list of all your disks with their respective capacity, usage, and more.

Answer 2

df -k | grep /dev/sda

will give you the size in KB (first number) as well as the space used (second number) and space available (third number)

Answer 3

fdisk doesn't understand the partition layout used by my Mac running Linux, nor any other non-PC partition format. (Yes, there's mac-fdisk, but that's not the only other partition layout out there.)

Since the kernel already scanned the partition layouts when the block device came into service, why not ask it directly?

$ cat /proc/partitions
major minor  #blocks  name

   8       16  390711384 sdb
   8       17     514079 sdb1
   8       18  390194752 sdb2
   8       32  976762584 sdc
   8       33     514079 sdc1
   8       34  976245952 sdc2
   8        0  156290904 sda
   8        1     514079 sda1
   8        2  155774272 sda2
   8       48 1465138584 sdd
   8       49     514079 sdd1
   8       50 1464621952 sdd2

Answer 4

cat /sys/class/block/sda/size

This gives you its size in 512-byte blocks.

Answer 5

echo `cat /sys/class/block/sda2/size`*512 | bc

gives size in byte

Answer 6

blockdev --getsize /dev/sda

Answer 7

This simple code. Couldn't find any documentation, but does the trick nicely:

#include <linux/fs.h>
...
ioctl(file, BLKGETSIZE64, &file_size_in_bytes);

Answer 8

blockdev --getsize64 /dev/sda returns size in bytes.

blockdev --getsize /dev/sda returns size in sectors.