Linux disk and file management

Linux disk and file management

In Linux O & M, O & M personnel mainly Manage Server I/O devices: disks and NICs. Here we mainly introduce disk management.

Everything in Linux is a file, and the hardware device also has a corresponding file. Accessing a device in Linux is actually accessing the corresponding file interface.

File interfaces: open (), read (), write (), close (), and so on.

Device Type:

Block: random access. The data exchange unit is block"

Character device (character): a linear device. The unit of data exchange is "character ". For example, enter the keyboard

Device Files: FHS (hierarchical standard for file systems)

In Linux, the/dev/directory is used to store device files. The device files are associated with the device driver and the device access portal.

Device management: Device number

Device No.: main device No. (major), sub-device No. (minor)

Major: Specifies the device type, which is used to indicate the required driver.

Minor: a specific device (c, character, and B) driven by drivers for different devices of the same type)

Linux disk device file name:

IDE (ATA): 133 MB/s,/dev/hd

SCSI: 640 MB/s

SATA: 6 Gbps

SAS: 6 Gbps

USB: 480 MB/s

Identify hard drive devices in Linux except IDE:/dev/sd

Mark Different Hard Drive devices:/dev/sd [a-z]

Mark different partitions on the same device:/dev/sd [a-z] [1-]

1-4: primary or extended partition ID

5 +: Logical partition ID

Mechanical hard drive Introduction: track, sector, cylinder cylindrical

MBR: 0 channels, 0 sectors, master boot record)

MBR is divided into three parts: 446 bytes: bootloader, boot program

64 bytes: partitioned table

16 bytes: Mark a partition

2 bytes: 55AA. indicates whether the MBR information is valid.

If a single hard disk exceeds 2 TB, you cannot use MBR partitioning. You can only use GPT partitioning.

Partitioning: separates buckets into multiple small spaces. Each space can use a file system independently;

Partition tool:

Fdisk, parted, sfdisk

Use of the fdisk tool:

Fdisk supports up to 15 partitions on one hard disk;

Fdisk partition management sub-command:

M: get help to display sub-commands

P: displays existing partition tables.

N: Create

D: Delete

T: Modify the partition ID.

L: list all supported ID types

W: Save and exit

Q: discard the modification and exit

After the partition is created, check whether the kernel recognizes the new partition:

# Cat/proc/partitions

There are three commands for the kernel to re-read the disk partition table:

CentOS 5: partprobe [DEVICE]

CentOS 6, 7:

Partx

Kpartx

Partx command: Note: The partition on the mounted hard disk must be executed. You may need to run the command twice or more times to read the partition successfully.

Partx DEVICE

Partx-a DEVICE

Partx-a-n M: N DEVICE

M

M:

: N

Kpartx command:

Kpartx-af DEVICE

After creating a partition, you must create a file system and format it.

For more details, please continue to read the highlights on the next page:

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