Jun 042013

While installing a new computer (soon a post on my new arch-linux laptop) I’ve re-discovered a command that I don’t use frequently, but that can be really useful : lsblk

lsblk lists information about all or the specified block devices. The lsblk command reads the sysfs filesystem to gather information.
The command prints all block devices (except RAM disks) in a tree-like format by default.

This command can be very useful to check how the different partitions and/or disks are mounted in the system, this is an example on my desktop:

sda       8:0    0 465.8G  0 disk   
├─sda1    8:1    0  46.6G  0 part   /
├─sda2    8:2    0     1K  0 part   
├─sda5    8:5    0   3.7G  0 part   [SWAP]
└─sda6    8:6    0 415.5G  0 part   
sdb       8:16   0 465.8G  0 disk   
└─sdb1    8:17   0 465.8G  0 part   
  └─md0   9:0    0 465.7G  0 raid10 /data
sdc       8:32   0 465.8G  0 disk   
└─sdc1    8:33   0 465.8G  0 part   
  └─md0   9:0    0 465.7G  0 raid10 /data
sdd       8:48   1  14.9G  0 disk   
└─sdd1    8:49   1  14.9G  0 part   /media/linuxaria/KINGSTON
sr0      11:0    1  1024M  0 rom

From this output you can see that on this desktop I’ve the following disks:

SDA the fist “scsi” disk, in my case a SATA disk.
On this disk the first partition is used for the / filesystem, the second partition it’s an extended partition, the third it’s my swap partition and the last one (sda6) is used for my /home, it’s a BTRFS filesystem and the command don’t recognize it,

SDB and SDC are the two disks that I use in RAID 10 and the filesystem is mounted as /data

SDD it’s an USB stick of 16GB mounted under the directory /media/linuxaria/KINGSTON

An output of a computer with LVM could be:

$ lsblk
NAME                       MAJ:MIN RM   SIZE RO MOUNTPOINT
sda                          8:0    0 298.1G  0
├─sda1                       8:1    0   500M  0 /boot
└─sda2                       8:2    0 297.6G  0
  ├─vg_main-lv_swap (dm-0) 253:0    0   5.8G  0 [SWAP]
  ├─vg_main-lv_root (dm-1) 253:1    0    50G  0 /
  └─vg_main-lv_home (dm-2) 253:2    0 241.8G  0
    └─home (dm-3)          253:3    0 241.8G  0 /home
sr0                         11:0    1  1024M  0

So as you can see this command it’s really easy to use and the output it’s really polish in its tree style, with a glance you can recognize partitions, logical volume and other useful information of your disks.
Running fdisk -l gives similar data. But, fdisk requires root privileges, and It does not understand dm or lvm partitions.

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