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In Linux, how are files stored, how is the logical composition of disk partitions realized, and how to partition, format, and mount the disk?

How the file is stored in the block group super block group description symbol

The file system is first divided into multiple block groups and super blocks. Each block group contains inode and data block, and each block group also contains inode bitmap and block bitmap;. Each block group also includes a block group descriptor.

The super block contains information such as volume label, mount time, UUID, magic number, file system characteristics, default options for mounting, file system status, OS type, related quantity of Inode and Block, size, available quantity, reserved space, and so on. Use tune2fs-l / dev/sda3 to view information about the super block.

GDT: records the number of unused inodes, the location of inode bitmap and datablock bitmap, the location of the inode table, and the number of free block and inode. Dumpe2fs / dev/sda3 | less can also use the-h parameter

What are the characteristics of the two linked files?

Hard links: multiple file paths to the same inode

Features: directories do not support the creation of hard links, hard links cannot be created across partitions, and creating hard links increases the inode reference count.

Ln passwd.back passwd.back2

Soft link: another file path that points to one file path

For a normal file, the inode pointer points to the location of the datablock, while the soft link points to the path of another file. The soft link in the file size is the number of bytes of the file path it points to.

Ln-s passwd.back passwd.sylink

[root@localhost tmp] # ls-il

Total dosage 12

33554511-rwx-. 1 root root 836 February 29 09:50 ks-script-XVVd4f

33554501-rw-r--r--. 2 root root 1099 March 1 11:37 passwd.back

33554501-rw-r--r--. 2 root root 1099 March 1 11:37 passwd.back2

33578842 lrwxrwxrwx. 1 root root 11 March 1 11:38 passwd.sylink-> passwd.back

Partition formatting mke2fs

Mke2fs [OPTIONS] device

-t {ext2 | ext3 | ext4}: indicates the type of file system to be created

Mkfs.ext4 = mkfs-t ext4 = mke2fs-t ext4

-b {1024 | 2048 | 4096}: indicates the block size of the file system

-L LABEL: indicates the volume label

-j: create a journaling file system ext3

Mke2fs-j = mke2fs-t ext3 = mkfs-t ext3 = mkfs.ext3

-I #: bytes-per-inode, indicating the ratio of inode to bytes; that is, creating an Indode for every number of bytes

By default, one inode for every 16K byte

-N #: directly indicates the number of inode to be created for this file system

-m #: specify reserved space, percentage

-O [^] FEATURE: creates the target file system with the specified properties

[root@localhost tmp] # mke2fs-t ext3-b 4096-L lq_data-I 32768-m 3 / dev/sda3

Mke2fs 1.42.9 (28-Dec-2013)

File system label = lq_data

OS type: Linux

Block size = 4096 (log=2)

Chunk size = 4096 (log=2)

Stride=0 blocks, Stripe width=0 blocks

655360 inodes, 5242880 blocks

157286 blocks (3.00%) reserved for the super user

First data block = 0

Maximum filesystem blocks=4294967296

160 block groups

32768 blocks per group, 32768 fragments per group

4096 inodes per group

Superblock backups stored on blocks:

32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208

4096000

Allocating group tables: done

Writing inode table: complete

Creating journal (32768 blocks): complete

Writing superblocks and filesystem accounting information: done

Master Fdisk Partition

Please complete the experiment.

What is stored in the metadata area

The metadata area stores inode inode bitmaps and block bitmaps

Datastores are disk blocks.

Inode stores information about the permissions and attributes of the file. You can use stat / etc/passwd to view the metadata information of a file.

How to make the kernel recognize the new partition parx kpartx

Cat / proc/partitions

When we have partitioned a disk using fdisk and formatted the partition using the mke2fs tool, we need to let the kernel recognize our new partition.

At this point, you can use cat / proc/partitions to see if the kernel recognizes this partition.

If it is not recognized, ask the kernel to reread the partition information.

A. partx-tell the Linux kernel about the presence and numbering of on-disk partitions

-an Add the specified partitions, or read the disk and add all partitions.

Usage: partx-a / dev/sda

B. kpartx-Create device maps from partition tables

-an Add partition mappings

Usage: kpartx-a / dev/sda

If it doesn't come out once, please brush it again.

Create a swap partition and take effect

Mkswap / dev/sda6

Swapon

Create a 5G swap partition

Blkid locates or displays the attributes of the block device.

[root@localhost ~] # blkid / dev/sda3

Dev/sda3: LABEL= "lq_data" UUID= "f80f0e3d-9ccb-43a2-ac30-98722a8a6ea2" TYPE= "ext3"

[root@localhost] # blkid-L lq_data

/ dev/sda3

[root@localhost] # blkid-U f80f0e3d-9ccb-43a2-ac30-98722a8a6ea2

/ dev/sda3

[root@localhost] # blkid-t TYPE=ext3

/ dev/sda3: LABEL= "lq_data" UUID= "f80f0e3d-9ccb-43a2-ac30-98722a8a6ea2" TYPE= "ext3

E2label view and set the volume label. If you do not follow the volume label, you will view the volume label. If you follow the volume label, you will set a new volume label.

E2label device [LABEL]

[root@localhost ~] # e2label / dev/sda3

Lq_data

[root@localhost ~] # e2label / dev/sda3 DATA

[root@localhost ~] # e2label / dev/sda3

DATA

[root@localhost ~] # blkid / dev/sda3

Dev/sda3: LABEL= "DATA" UUID= "f80f0e3d-9ccb-43a2-ac30-98722a8a6ea2" TYPE= "ext3"

Tune2fs: adjust file system parameters on ext series file systems, of which-O and-o are the most useful

-l view the contents of the super block

-j upgrade ext2 to ext3, lossless upgrade

-L sets the volume label

-m is not formatted, adjust the percentage of reserved space, default is 5%

-O [^] feature adjusts the specified property

-o adjust default mount options

Tune2fs-o acl / dev/sda5

[root@localhost] # mke2fs-t ext2-L TEST-m 10 / dev/sda3

Next, we adjust the properties of the file system through tune2fs, which I first try to do in the mount state.

[root@localhost ~] # mount / dev/sda3 / mnt

a. Upgrade the file system type to ext3

[root@localhost] # tune2fs-j / dev/sda3

Tune2fs 1.42.9 (28-Dec-2013)

Creating journal inode: done

[root@localhost ~] # blkid / dev/sda3

Dev/sda3: LABEL= "TEST" UUID= "96361554-d8a3-43cb-860d-45ce26daaeff" SEC_TYPE= "ext2" TYPE= "ext3"

b. Set the volume label to Corun

[root@localhost] # tune2fs-L Corun / dev/sda3

Tune2fs 1.42.9 (28-Dec-2013)

[root@localhost ~] # blkid / dev/sda3

Dev/sda3: LABEL= "Corun" UUID= "96361554-d8a3-43cb-860d-45ce26daaeff" SEC_TYPE= "ext2" TYPE= "ext3"

c. Change the percentage of space reserved to 2%

[root@localhost] # tune2fs-m 2 / dev/sda3

Tune2fs 1.42.9 (28-Dec-2013)

Setting reserved blocks percentage to 2% (104857 blocks)

Dumpe2fs: displays attribute information for ext series file systems

Dumpe2fs / dev/sda5

Dumpe2fs-h / dev/sda5

Fsck and e2fsck

Special tools for ext series file systems:

E2fsck: check a Linux ext2/ext3/ext4 file system

E2fsck [OPTIONS] device

-y: automatically answer yes to all questions

-f: force detection even if the file system is in the clean state

Fsck:check and repair a Linux file system

-t fstype: indicates the file system type

Fsck-t ext4 = fsck.ext4

-a: automatically fix all errors without interaction

-r: interactive repair

Mounting and unmounting of file system

Mount DEVICE DIR

Umount DEVICE | DIR

Example:

Mount / dev/sda3 / mnt

Umount / dev/sda3

Nan should note that the mount point should be an empty directory, and it is recommended that you place the mount point on the file system where the root is located.

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