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Storage Devices

/dev​

Each device on system is represented by a file in the /dev directory.

Notable devices are:

  • Hard drive for newer disk technologies such as SATA and SCSI are named with sd prefix. Older Linux machines used hd for hard drives. The file system treats each hard drive as a different device with an appended letter:

sda - First SATA hard drive. sda - Second SATA hard drive.

  • Drives are sometimes split up into partitions and are represented by numbers in the end of the name:
    sda1 - First partition of first SATA hard drive
    
    sda2 - Second partition of first SATA hard drive

To view more information about block devices how much capacity each drive can hold:

fdisk -l
lsblk

Character and Block devices​

Devices can transfer data in and out in two ways.

ls -latr /dev

crw-rw-rw-   1 root   wheel           24,  22 Jul 22 20:04 dtrace
brw-r-----   1 root   operator         1,   8 Jul 22 20:04 disk1s6

The c in the permission list row indicates that the dtrace device is a chatacter device which sends and receives data character by character such as mice and keyboards.

The b indicates the device sends and receives data in blocks of bytes. Hard drives and USB sticks are block devices which have higher data throughput.

Mounting Devices​

A storage device must be first physically connected then logically connected in order to be available for the filesystem. The mount point is the location where devices are attached. External USB drives are usually /media while internal hard drives are mounted in /mnt.

To mount a device:

mount /dev/sdb1 /mnt

Mount point should be empty!

The filesystems that are mounted are kept in /etc/fstab

To unmount:

umount /dev/sdb1

We can run df to retrieve information about free and used space of any devices/hard drives.

Repairing a device​

First need to unmount a device and then run:

# -p automatically repairs device
fsck -p /dev/sdb1