"Turn"/etc/fstab function detailed

"Turn"/etc/fstab function detailed

Recently went to the customer site, encountered a question about mount file /etc/fstab file, wrote a /etc/fstab file of the role of each parameter in the meaning of a file. Please correct me if you have any reference to the wrong place.

I. the role of/etc/fstab files

after the disk is manually mounted, the mount information must be written to the/etc/fstab file, or it will still need to be mounted again the next time the boot starts.

when the system is powered on, it will actively read the contents of the /etc/fstab file, and mount the disk according to the configuration in the file. So we just need to write the disk's mount information to this file and we don't have to mount it manually after each boot.

Ii. Restrictions on Mount

Before I explain the effect of this file, I would like to highlight the mounting restrictions.

1, the root directory must be mounted, and must be mounted before the other mount point . Because Mount is the directory of all directories, all other wood is derived from the root directory .

2. Mount point must be a directory that already exists.

3, Mount point designation can be arbitrary, but must abide by the necessary system directory architecture principles

4. All mount points can only be mounted once at the same time

5. All partitions can only be hung at once at the same time

6. If you uninstall, you must leave the working directory outside the Mount point (and its subdirectories).

Iii. parameters in the/etc/fstab file

Let's look at the /etc/fstab file, which is the contents of the /etc/fstab file in my Linux environment

[Email protected] ~]# Cat/etc/fstab

# This file was edited by Fstab-sync-see ' Man Fstab-sync ' for details

# Device Mount point filesystem parameters Dump fsck

label=//ext3 Defaults 1 1

Label=/boot/boot ext3 Defaults 1 2

None/dev/pts devpts gid=5,mode=620 0 0

NONE/DEV/SHM TMPFS Defaults 0 0

NONE/PROC proc Defaults 0 0

None/sys Sysfs Defaults 0 0

Label=swap-sda3 swap swap defaults 0 0

/dev/sdb1/u01 ext3 Defaults 1 2

uuid=18823fc1-2958-49a0-9f1e-e1316bd5c2c5/u02 ext3 Defaults 1 2

/dev/hdc/media/cdrom1 Auto pamconsole,exec,noauto,managed 0 0

/dev/fd0/media/floppy Auto pamconsole,exec,noauto,managed 0 0

In the file I have made each column to make it easy to identify, we can see a total of six columns.

First list of Device

disk device file or the Label or UUID of the device

1) View the label and uuid of the partition

Label is the label of the partition, in the initial installation of the system is filled with the mount point is the name of the label. You can find the UUID and Label name by looking at the information in the superblock of a partition.

For example we want to see the uuid and label name of the /DEV/SDA 1 device

[Email protected] u02]# dumpe2fs-h/dev/sda1

DUMPE2FS 1.35 (28-feb-2004)

Filesystem volume Name: /boot// This is the Label name

Last mounted on:

Filesystem uuid:3b10fe13-def4-41b6-baae-9b4ef3b3616c //uuid

Filesystem Magic number:0xef53

Filesystem Revision #: 1 (dynamic)

Filesystem features:has_journal ext_attr resize_inode dir_index filetype needs_recovery sparse_super

Default mount options: (None)

Filesystem State:clean

In a simple way, we can use the following command to view

[Email protected] u02]# blkid/dev/sda1

/dev/sda1:label= "/boot" uuid= "3b10fe13-def4-41b6-baae-9b4ef3b3616c" sec_type= "ext3" type= "ext2"

2) Use the device name and label and uuid as the different identification

The use of the device name (/DEV/SDA) to mount the partition is fixed dead, once the disk slot order has changed, there will be a problem with the name does not correspond. Because this name is going to change.

However, using a label mount does not worry about slot order issues. But keep an eye on your Label name.

As for UUID, each partition will have a uuid as its unique identification number after it is formatted. Use the uuid to mount the words without worrying about the problem of confusion.

Second row, Mount Point

The mount point of the device is the directory you want to mount to.

Column three filesystem

Format of the disk file system, including ext2,ext3,reiserfs,NFS, VFAT, etc.

Fourth column parameters

File system Parameters

Async/sync	Set whether to run synchronously, default to async
Auto/noauto	whether the file system is actively mounted when the MOUNT-A command is downloaded. Default is auto
Rw/ro	whether to mount in read-only or read-write mode
Exec/noexec	restricting the ability to perform operations within this file system
User/nouser	Whether the user is allowed to mount using the Mount command
Suid/nosuid	Whether to allow the existence of SUID
Usrquota	Boot file system supports disk quota mode
Grpquota	Boot file system support for group disk quota mode
Defaults	Colleagues with RW, Suid,dev,exec,auto,nouser,async and other default parameters settings

The fourth column: can be the dump backup command function

Dump is a command that is used as a backup. Usually the value of this parameter is 0 or 1

0	Rep don't do dump backup
1	Represents a daily dump operation
2	Perform a dump operation that represents an indefinite date

Whether the sixth column examines sectors

During the boot process, the system defaults to fsck to Verify that our system is complete (clean).

0	Do not test
1	First Test (Common root directory selection)
2	Inspection after completion of the 1 level inspection

"Turn"/etc/fstab function detailed