rhel7磁盘管理

2023-01-31 10:56:29

一、MBR主引导记录
MBR有512个字节，分为三个部分：第一部分446个字节，存储了引导分区；第二部分64字节为分区表；第三部分2个字节结束符；每个分区需16个字节，所以MBR的模式下只能划分4个主分区或3个主分区和扩展分区；主分区可以直接使用，扩展分区不能直接使用，在扩展分区上划分逻辑分区再使用；

[root@wk ~]# cat /proc/partitions

major minor #blocks name

8 16 20971520 sdb

8 0 26214400 sda

8 1 1024000 sda1

8 2 18432000 sda2

8 3 1024000 sda3

11 0 3655680 sr0

二、GPT
GPT可以记录128个主分区；
三、使用命令管理磁盘分区
1、fdisk命令
使用fdisk划分磁盘，默认会划分为MBR格式的磁盘
fdisk -l 查看当前的磁盘和分区情况：

[root@wk ~]# fdisk /dev/sdb

Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.

Be careful before using the write command.

Device does not contain a recognized partition table

Building a new DOS disklabel with disk identifier 0x39c77fae.

Command (m for help): m

Command action
a toggle a bootable flag
b edit bsd disklabel
c toggle the dos compatibility flag
d delete a partition 删除分区
g create a new empty GPT partition table
G create an IRIX (SGI) partition table
l list known partition types 列出分区类型
m print this menu 打印帮助菜单
n add a new partition 添加一个新分区
o create a new empty DOS partition table
p print the partition table 打印分区表
q quit without saving changes
s create a new empty Sun disklabel
t change a partition's system id
u change display/entry units
v verify the partition table
w write table to disk and exit 退出并保存，然后使用partprobe或partx /dev/sdX刷新
x extra functionality (experts only)
添加分区：

Command (m for help): n

Partition type:

p primary (0 primary, 0 extended, 4 free)

e extended

Select (default p): p

Partition number (1-4, default 1):

First sector (2048-41943039, default 2048):

Using default value 2048

Last sector, +sectors or +size{K,M,G} (2048-41943039, default 41943039): +2G

Partition 1 of type Linux and of size 2 GiB is set

Command (m for help):p
Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 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

Disk label type: dos

Disk identifier: 0x39c77fae

Device Boot Start End Blocks Id System

/dev/sdb1 2048 4196351 2097152 83 Linux

Command (m for help):

只能划分四个主分区，如果要划分多余四个分区，则需要在第四个分区创建扩展分区，在扩展分区上创建逻辑分区：

Device Boot Start End Blocks Id System

/dev/sdb1 2048 4196351 2097152 83 Linux

/dev/sdb2 4196352 8390655 2097152 83 Linux

/dev/sdb3 8390656 12584959 2097152 83 Linux

/dev/sdb4 12584960 41943039 14679040 5 Extended

/dev/sdb5 12587008 16781311 2097152 83 Linux

[root@wk ~]# fdisk -l /dev/sda

有*标识代表的是启动分区：

Device Boot Start End Blocks Id System

/dev/sda1 * 2048 2050047 1024000 83 Linux

/dev/sda2 2050048 38914047 18432000 83 Linux

/dev/sda3 38914048 40962047 1024000 82 Linux swap / Solaris

分区类型，使用t命令可以修改分区的类型：
Command (m for help): l

0 Empty 24 NEC DOS 81 Minix / old Lin bf Solaris

1 FAT12 27 Hidden NTFS Win 82 Linux swap / So c1 DRDOS/sec (FAT-

2 XENIX root 39 Plan 9 83 Linux c4 DRDOS/sec (FAT-

3 XENIX usr 3c PartitionMagic 84 OS/2 hidden C: c6 DRDOS/sec (FAT-

4 FAT16 <32M 40 Venix 80286 85 Linux extended c7 Syrinx

5 Extended 41 PPC PReP Boot 86 NTFS volume set da Non-FS data

....省略

2、gdisk命令
使用gdisk划分磁盘，默认划分为GPT格式的磁盘

[root@wk ~]# gdisk /dev/sdb

GPT fdisk (gdisk) version 0.8.6

Partition table scan:

MBR: not present

BSD: not present

APM: not present

GPT: not present

Creating new GPT entries.

Command (? for help):
使用方法与fdisk基本相同，这里不在复述。

3、parted命令：可以自行选择划分格式
parted命令可以将MBR结构修改为GPT结构，但是要慎重，因为分区表会丢失：

[root@wk ~]# parted /dev/sdb

GNU Parted 3.1

Using /dev/sdb

Welcome to GNU Parted! Type 'help' to view a list of commands.

(parted) help------------查看下帮助吧，不常用记不住。

使用mklabel转换分区类型：
aix amiga bsd dvh gpt loop mac msdos pc98 sun
(parted) mklabel

New disk label type? gpt

(parted)

Command (m for help): w

The partition table has been altered!

Calling ioctl() to re-read partition table.

Syncing disks.

[root@wk ~]# partprobe 或 [root@wk ~]# partx -a
4、使用mkfs给分区设置文件系统：

[root@wk ~]# mkfs -t xfs /dev/sdb1

meta-data=/dev/sdb1 isize=256 agcount=4, agsize=131072 blks

= sectsz=512 attr=2, projid32bit=1

= crc=0

data = bsize=4096 blocks=524288, imaxpct=25

= sunit=0 swidth=0 blks

naming =version 2 bsize=4096 ascii-ci=0 ftype=0

log =internal log bsize=4096 blocks=2560, version=2

= sectsz=512 sunit=0 blks, lazy-count=1

realtime =none extsz=4096 blocks=0, rtextents=0

指定block size大小：

[root@wk ~]# mkfs.xfs -b size=1024 /dev/sdb2

挂载分区到文件系统：

[root@wk ~]# mkdir /aa

[root@wk ~]# mount /dev/sdb1 /aa

[root@wk ~]# df -h

Filesystem Size Used Avail Use% Mounted on

/dev/sda2 18G 14G 3.8G 79% /

devtmpfs 482M 0 482M 0% /dev

tmpfs 490M 0 490M 0% /dev/shm

tmpfs 490M 6.9M 484M 2% /run

tmpfs 490M 0 490M 0% /sys/fs/cgroup

/dev/sda1 997M 123M 875M 13% /boot

/dev/sdb1 2.0G 33M 2.0G 2% /aa

可以使用xfs_info查看文件系统信息：

[root@wk ~]# xfs_info /aa

meta-data=/dev/sdb1 isize=256 agcount=4, agsize=131072 blks

= sectsz=512 attr=2, projid32bit=1

= crc=0

data = bsize=4096 blocks=524288, imaxpct=25

= sunit=0 swidth=0 blks

naming =version 2 bsize=4096 ascii-ci=0 ftype=0

log =internal bsize=4096 blocks=2560, version=2

= sectsz=512 sunit=0 blks, lazy-count=1

realtime =none extsz=4096 blocks=0, rtextents=0
使用xfs_admin查看分区的blkid:

[root@wk ~]# xfs_admin -u /dev/sdb1

UUID = 12d99538-2241-42b0-b873-6406266cc8e2
也可以使用blkid查看：

[root@wk ~]# blkid

/dev/sdb1: UUID="12d99538-2241-42b0-b873-6406266cc8e2" TYPE="xfs" PARTUUID="e71103e9-668d-444b-bc96-70501467cc43"

/dev/sdb2: UUID="9a951c66-78e1-416e-aa0e-7d41a55efc6d" TYPE="xfs" PARTUUID="38a4a2ea-2571-419d-b80f-8ea801f4291e"

/dev/sda1: UUID="7dfc741a-395f-46d9-ba69-a037f24ae107" TYPE="xfs"

/dev/sda2: UUID="82934945-3802-4f45-ada3-1d43f0b2a1c5" TYPE="xfs"

/dev/sda3: UUID="6dde9ce3-2757-4c88-b082-5665daa2d584" TYPE="swap"

/dev/sr0: UUID="2014-05-07-03-58-46-00" LABEL="RHEL-7.0 Server.x86_64" TYPE="iso9660" PTTYPE="dos"

一个分区如果不格式的话，没有文件系统那么就不会有UUID：
可以使用xfs_admin -U修改分区的UUID：
[root@wk ~]# uuidgen
292e2919-11fa-4f1c-8006-4a506095d377
[root@wk ~]# xfs_admin -U 292e2919-11fa-4f1c-8006-4a506095d377 /dev/sdb1
Clearing log and setting UUID
writing all SBs
new UUID = 292e2919-11fa-4f1c-8006-4a506095d377
xfs文件系统大小可以增加，但是不能减少

Swap交换分区，类似于Windows的虚拟内存：
就是利用磁盘里面的一部分空间，来模拟内存：
1、使用分区；
2、创建文件；
查看Swap分区:

[root@wk ~]# cat /proc/swaps

Filename Type Size Used Priority

/dev/sda3 partition 1023996 0 -1

命令t修改分区为swap格式：

Command (m for help): t

Selected partition 1

Partition type (type L to list all types): 14

Changed type of partition 'EFI System' to 'Linux swap'

格式化swap分区：

[root@wk ~]# mkswap /dev/sdb1

mkswap: /dev/sdb1: warning: wiping old xfs signature.

Setting up swapspace version 1, size = 1048572 KiB

no label, UUID=b633a131-d314-487b-b1f8-a5516626c081
使用Swapon 和 Swapoff 启用或关闭swap分区：

[root@wk ~]# swapon /dev/sdb1

[root@wk ~]# free

total used free shared buffers cached

Mem: 1003456 420340 583116 7020 1328 138184

-/+ buffers/cache: 280828 722628

Swap: 2072568 0 2072568

[root@wk ~]# swapoff /dev/sdb1

[root@wk ~]# free

total used free shared buffers cached

Mem: 1003456 419936 583520 7020 1324 138220

-/+ buffers/cache: 280392 723064

Swap: 1023996 0 1023996

创建文件作为swap分区：

[root@wk ~]# dd if=/dev/zero of=/swapfile bs=1M count=200

[root@wk ~]# mkswap /swapfile

Setting up swapspace version 1, size = 204796 KiB

no label, UUID=630ac3d6-94fd-4b68-8148-00f0b780bb2d
[root@wk ~]# chmod 0600 /swapfile

[root@wk ~]# swapon /swapfile

[root@wk ~]# free

total used free shared buffers cached

Mem: 1003456 630596 372860 7016 1328 343160

-/+ buffers/cache: 286108 717348

Swap: 1228792 0 1228792

[root@wk ~]# swapoff /swapfile

[root@wk ~]# free

total used free shared buffers cached

Mem: 1003456 630556 372900 7016 1328 343160

-/+ buffers/cache: 286068 717388

Swap: 1023996 0 1023996

最后，记得在 /etc/fstab中添加相应参数

[root@wk ~]# cat /etc/fstab

# /etc/fstab

# Created by anaconda on Fri Jan 1 11:14:17 2016

# Accessible filesystems, by reference, are maintained under '/dev/disk'

# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info

UUID=82934945-3802-4f45-ada3-1d43f0b2a1c5 / xfs defaults 1 1

UUID=7dfc741a-395f-46d9-ba69-a037f24ae107 /boot xfs defaults 1 2

UUID=6dde9ce3-2757-4c88-b082-5665daa2d584 swap swap defaults 0 0
这部分就不介绍了，查一下吧。

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