Examining partitions on Linux systems

Linux systems provide many ways to look at disk partitions. In this post, we’ll look at a series of commands, each which shows useful information but in a different format and with a different focus. Maybe one will make your favorites list.

lsblk

One of the most useful commands is the lsblk (list block devices) command that provides a very nicely formatted display of block devices and disk partitions. In the example below, we can see that the system has two disks (sda and sdb) and that sdb has both a very small (500M) partition and a large one (465.3G). Disks and partitions (part) are clearly labeled, and the relationship between the disks and partitions is quite obvious. We also see that the system has a cdrom (sr0).

$ lsblk | grep -v loop
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0 111.8G  0 disk
└─sda1   8:1    0 111.8G  0 part /
sdb      8:16   0 465.8G  0 disk
├─sdb1   8:17   0   500M  0 part
└─sdb2   8:18   0 465.3G  0 part /apps
sr0     11:0    1  1024M  0 rom

[ Two-Minute Linux Tips: Learn how to master a host of Linux commands in these 2-minute video tutorials]

A block device is a device that the system reads and writes one block of data at a time unlike, for example, character and serial devices. The command above is skipping over loop devices with the grep -v command.

cat /proc/partitions

Looking at the partitions file shows similar data, but not in as nearly a useful format. Partitions and disks sizes are reported in blocks. It does, however, show the major and minor device numbers. Note that we are again selecting lines (only those containing an “s”) to omit loop devices.

$ cat /proc/partitions | grep s
major minor  #blocks  name
   8        0  117220824 sda
   8        1  117219328 sda1
  11        0    1048575 sr0
   8       16  488386584 sdb
   8       17     512000 sdb1
   8       18  487872512 sdb2

df

The df (disk usage) command can provide a succinct report on disk partitions, but only mounted partitions. It shows file system sizes along with measurements of how much of the disk space is used. In this example, we’re using -h (human-readable size measurements), -T (include partition type), and -t (select partitions of the specified type) options.

$ df -hTt ext4
Filesystem     Type  Size  Used Avail Use% Mounted on
/dev/sda1      ext4  110G  9.0G   95G   9% /
/dev/sdb2      ext4  457G   73M  434G   1% /apps

mount

Another command for listing file systems that are mounted along with their types and mount options is the mount command itself. This command shows us nothing about partition sizes, but the options are interesting.

$ mount | grep ^/dev
/dev/sda1 on / type ext4 (rw,relatime,errors=remount-ro,data=ordered)
/dev/sdb2 on /apps type ext4 (rw,relatime,data=ordered)

In the above output, we see the partitions, mount points, file system type, and these options:

• rw — read/write
• relatime — access time (atime) will not be written to the disc during every access
• errors=remount-ro — file system will be remounted as read-only if errors are detected
• data=ordered — file data written to file system prior to metadata being committed to the journal

The remount-ro choice is specified in the /etc/fstab file. The tune2fs command allows us to adjust other file system parameters.

fdisk

The fdisk command provides ways to manipulate disk partitions, but with the -l option, we are only displaying partition descriptions on ext2, ext3 and ext4 file systems.

$ sudo fdisk -l /dev/sda1
Disk /dev/sda1: 111.8 GiB, 120032591872 bytes, 234438656 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

$ sudo sfdisk -l /dev/sda1
Disk /dev/sda1: 111.8 GiB, 120032591872 bytes, 234438656 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

parted

Like sfdisk, the parted command allows us to manipulate partitions but offers a -l option for displaying partition descriptions.

$ sudo parted -l
Model: ATA SSD2SC120G1CS175 (scsi)
Disk /dev/sda: 120GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:

Number  Start   End    Size   Type     File system  Flags
 1      1049kB  120GB  120GB  primary  ext4         boot


Model: ATA SAMSUNG HE502HJ (scsi)
Disk /dev/sdb: 500GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:

Number  Start   End    Size   Type     File system  Flags
 1      1049kB  525MB  524MB  primary  ntfs         boot
 2      525MB   500GB  500GB  primary  ext4

blkid

The blkid command displays block device attributes. It shows the 128-bit UUID and file system type, but it is not likely to be the most illuminating command for providing partition stats.

$ sudo blkid
/dev/sda1: UUID="235f8f0c-641a-4d83-b584-7280cfcd3faa" TYPE="ext4" PARTUUID="f63b5929-01"
/dev/sdb1: LABEL="System Reserved" UUID="08F0AF99F0AF8C0E" TYPE="ntfs" PARTUUID="7e67ccf3-01"
/dev/sdb2: UUID="94a29e41-b282-4ca2-aacb-fbd91507dc27" TYPE="ext4" PARTUUID="7e67ccf3-02"

hwinfo

The hwinfo command probes system hardware and provides a nicely organized display of disks, partitions and, if available, other block devices. This short report displays only a fraction of the information the command will report. The –block and the –short options specify that we only want the command to provide summaries on block devices.

$ hwinfo --block --short
disk:
  /dev/sdb             SAMSUNG HE502HJ
  /dev/sda             SSD2SC120G1CS175
partition:
  /dev/sdb1            Partition
  /dev/sdb2            Partition
  /dev/sda1            Partition
cdrom:
  /dev/sr0             HL-DT-ST DVD+-RW GSA-H73N

file

Even the file command can shed some light on partitions. In the example below, we see the partitions, file system types, and the 128 bit UUID numbers.

$ sudo file -s /dev/sda1
/dev/sda1: Linux rev 1.0 ext4 filesystem data, UUID=235f8f0c-641a-4d83-b584-7280cfcd3faa (needs journal recovery) (extents) (64bit) (large files) (huge files)
$ sudo file -s /dev/sdb2
/dev/sdb2: Linux rev 1.0 ext4 filesystem data, UUID=94a29e41-b282-4ca2-aacb-fbd91507dc27 (extents) (64bit) (large files) (huge files)

Wrap-up

Linux systems provide many ways to examine partition information. Which is best depends on what you’re looking for. Some commands look only at mounted file systems, while others provide copious details on the hardware.