硬盘的介绍和Linux磁盘的管理

清疚 2022-04-24 00:08 284阅读 0赞

*  SAS-SATA-SSD-SCSI-IDE硬盘讲解
 *  磁盘分区工具和挂载
 *  磁盘分区免交互方法
 *  扩展swap分区

# SAS-SATA-SSD-SCSI-IDE硬盘讲解 #

常见的磁盘类型：  
SAS硬盘；SATA硬盘；SCSI硬盘；SSD硬盘；IDE硬盘

**SAS硬盘：**

*  SAS（串行连接 SCSI 接口）
 *  SAS（Serial Attached SCSI），串行连接 SCSI接口，串行连接小型计算机系统接口。
 *  SAS 是新一代的 SCSI 技术，和现在流行的 SerialATA(SATA)硬盘相同，都是采用串行技术以获得 更高的传输速度，并通过缩 短连结线改善内部空间等。
 *  SAS 的接口技术可以向下兼容SATA。

**磁盘尺寸：**

*  3.5 英寸设计
 *  2.5 英寸设计

此前主流的桌面磁盘和服务器磁盘都是采用 3.5 英寸设计，而 SAS 硬盘除了具有传统的 3.5 英寸规  
栺之外，还采用了 2.5 英寸的缩小版，这样可以在机架式服务器有限的空间内安装更多的磁盘以扩充存储  
系统的容量，也能够为其他配件腾出更大的空间，以便通风散热，在 2U 高度内使用 8 个 2.5 英寸的 SAS  
硬盘位已经成为大多数服务器厂商的选择。

**当下流行的磁盘种类**  
常见硬盘品牌：希捷 西数 日立 HP DELL EMC IBM  
硬盘分几种？  
A. 从工作原理来说：  
固态：价栺相对贵，导命长，读取速度  
机械：怕摔、怕磁，（单位换下来的坏盘会做消磁处理），读取速度—》磁道寺址时间，潜伏时间  
B. 从硬盘的接口来说  
STAT：用在低端服务器多  
SAS、SCSI：用在中高服务器  
PCIE M.2  
对 LINUX 来说，在内核中，不同的接口对应有不同的命名方式：  
操作系统 IDE STAT|SCSI SAS  
RHEL5 /dev/hda /dev/sda /dev/sda  
RHEL6 /dev/sda /dev/sda /dev/sda  
KVM /dev/vda

# 磁盘的分区和挂载 #

1、硬盘分区符的认识  
MBR 概述：全称为 Master Boot Record，即硬盘的主引寻记录。  
硬盘的 0 柱面、0 磁头、1 扇区称为主引寻扇区（也叫主引寻记录 MBR）。它由三个部分组成，主引导程序、硬盘分区表 DPT（Disk Partition table）和分区有效标志（55AA）。在总共 512 字节的主引导扇区里主引导程序（boot loader）占 446 个字节，第二部分是 Partition table 区（分区表），即 DPT，占 64 个字节，硬盘中分区有多少以及每一分区的大小都记在其中。第三部分是 magic number，占 2 个字节，固定为 55AA。  
分区编号：主分区 1-4 ，逻辑分区 5……  
LINUX 规定：逻辑分区必须建立在扩展分区之上，而不是建立在主分区上  
分区作用：  
主分区：主要是用来启动操作系统的，它主要放的是操作系统的启动或引导程序，/boot 分区最好放在主分区上  
扩展分区不能使用的，它只是做为逻辑分区的容器存在的；我们真正存放数据的是主分区和逻辑分区，大量数据都放在逻辑分区中  
如果你用的是 GPT 的分区方式，那么它没有限制主分区个数

2、使用fdisk管理分区  
fdisk：磁盘翻去，是Linux发行版本中最常用的分区工具  
常用选项：

*  d：删除已创建的分区
 *  l：查看硬盘分区表
 *  n：创建分区
 *  p：打印分区表
 *  w：保存创建的分区表
 *  q：退出，不保存
 *  m：帮助菜单
 *  t：更改分区的系统类型
 *  v：验证分区表

**例1：添加一块磁盘，进行分区**  
因为在生产环境中，我们一般添加硬盘都是热插拔形式的，不能重启服务器来识别硬盘，所有需要使用到如下命令扫描硬盘：

> \[root@xuegod140 ~\]\# echo “- - -” >> /sys/class/scsi\_host/host0/scan

上述命令可以将在不重启服务器的基础上，将新增加的硬盘扫描出来，因为scsi\_host目录下有很多个host目录，所以我们需要一个个扫描，知道将增加的硬盘扫描出来为止。

面交互的扫描硬盘的两种命令：

> \[root@xuegod140 ~\]\# for i in /sys/class/scsi\_host/host\*/scan; do echo “- - -” > $i; done

磁盘分区后，有的分区因为没有加载到内存中，需要使用命令刷下后，才可以显示：

> \[root@xuegod140 ~\]\# partprobe -a /dev/sdb \#或者下面的命令  
> \[root@xuegod140 ~\]\# partx -a /dev/sdb

GPT格式硬盘转换成MBR格式硬盘命令：

> \[root@xuegod140 ~\]\# parted -s /dev/sdb mklabel msdos

MBR格式硬盘转换成GPT硬盘命令：

> \[root@xuegod140 ~\]\# parted -s /dev/sdb mklabel gpt

**例1：使用fdisk命令将磁盘进行分区，默认是MBR格式分区**

> \[root@xuegod140 ~\]\# fdisk /dev/sdb \#对磁盘进行分区格式化  
> 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.  
> Command (m for help): n  
> Partition type:  
> p primary (0 primary, 0 extended, 4 free)  
> e extended  
> Select (default p): p \#p创建主分区  
> Partition number (1-4, default 1): \#默认1号分区，回车  
> First sector (2048-41943039, default 2048): @默认扇区开始，回车  
> Using default value 2048  
> Last sector, +sectors or +size\{K,M,G\} (2048-41943039, default 41943039): +300M \#指定大小为300M  
> Partition 1 of type Linux and of size 300 MiB is set  
> Command (m for help): w \# w保存分区表  
> The partition table has been altered!  
> Calling ioctl() to re-read partition table.  
> Syncing disks.  
> \[root@xuegod140 ~\]\# lsblk  
> NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT  
> sda 8:0 0 20G 0 disk  
> ├─sda1 8:1 0 500M 0 part /boot  
> ├─sda2 8:2 0 10G 0 part /  
> └─sda3 8:3 0 4G 0 part \[SWAP\]  
> sdb 8:16 0 20G 0 disk  
> └─sdb1 8:17 0 300M 0 part  
> sdc 8:32 0 20G 0 disk  
> sr0 11:0 1 4.2G 0 rom /mnt

注释说明：  
MBR格式的分区最多可以创建4个主分区；也可以创建3个主分区，一个扩展分区，然后在扩展分区的基础上，最多可以创建11个逻辑分区

**例2：创建一个扩展分区**

> \[root@xuegod140 ~\]\# 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.  
> Command (m for help): p \#打印分区表  
> 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: 0x0000216c  
> Device Boot Start End Blocks Id System  
> /dev/sdb1 2048 616447 307200 83 Linux  
> Command (m for help): n \#创建分区表  
> Partition type:  
> p primary (1 primary, 0 extended, 3 free)  
> e extended  
> Select (default p): e \#创建扩展分区  
> Partition number (2-4, default 2):  
> First sector (616448-41943039, default 616448):  
> Using default value 616448  
> Last sector, +sectors or +size\{K,M,G\} (616448-41943039, default 41943039): +10G \#指定大小10G  
> Partition 2 of type Extended and of size 10 GiB is set  
> Command (m for help): w \#保存分区表  
> The partition table has been altered!  
> Calling ioctl() to re-read partition table.  
> Syncing disks.  
> 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: 0x0000216c  
> Device Boot Start End Blocks Id System  
> /dev/sdb1 2048 616447 307200 83 Linux  
> /dev/sdb2 616448 21587967 10485760 5 Extended

**例3：在扩展分区的基础上，创建一个逻辑分区**

> \[root@xuegod140 ~\]\# 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.  
> 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: 0x0000216c  
> Device Boot Start End Blocks Id System  
> /dev/sdb1 2048 616447 307200 83 Linux  
> /dev/sdb2 616448 21587967 10485760 5 Extended  
> Command (m for help): n  
> Partition type:  
> p primary (1 primary, 1 extended, 2 free)  
> l logical (numbered from 5)  
> Select (default p): l \#创建逻辑分区  
> Adding logical partition 5  
> First sector (618496-21587967, default 618496):  
> Using default value 618496  
> Last sector, +sectors or +size\{K,M,G\} (618496-21587967, default 21587967): +300M  
> Partition 5 of type Linux and of size 300 MiB 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: 0x0000216c  
> Device Boot Start End Blocks Id System  
> /dev/sdb1 2048 616447 307200 83 Linux  
> /dev/sdb2 616448 21587967 10485760 5 Extended  
> /dev/sdb5 618496 1232895 307200 83 Linux  
> Command (m for help): w  
> The partition table has been altered!  
> Calling ioctl() to re-read partition table.  
> Syncing disks.

**例4：使用gdisk命令，将磁盘进行分区，分区格式是GPT格式**  
gdisk 主要是用来划分容量大于 2T 的硬盘,大于 2T fdisk 搞不定  
两种类型的分区表：GPT 和 MBR ； MBR 不支持 4T 以上  
GPT 分区：GPT，全局唯一标识分区表(GUID Partition Table)，它使用 128 位 GUID 来唯一标识每个磁盘和分区，与MBR 存在单一故障点不同，GPT 提供分区表信息的冗余，一个在磁盘头部一个在磁盘尾部；它通过 CRC校验和来检测 GPT 头和分区表中的错误与损坏；默认一个硬盘支持 128 个分区

> \[root@xuegod140 ~\]\# gdisk /dev/sdc  
> 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): n \#创建新分区  
> Partition number (1-128, default 1): \#最大可以创建128个，默认从1开始  
> First sector (34-41943006, default = 2048) or \{±\}size\{KMGTP\}: \#从默认扇区开始  
> Last sector (616448-41943006, default = 41943006) or \{±\}size\{KMGTP\}: +300M \#指定大小300M  
> Current type is ‘Linux filesystem’  
> Hex code or GUID (L to show codes, Enter = 8300):  
> Changed type of partition to ‘Linux filesystem’  
> Command (? for help): p \#打印分区表  
> Disk /dev/sdc: 41943040 sectors, 20.0 GiB  
> Logical sector size: 512 bytes  
> Disk identifier (GUID): A0D74468-9C24-4727-ADF0-A9FFA3468988  
> Partition table holds up to 128 entries  
> First usable sector is 34, last usable sector is 41943006  
> Partitions will be aligned on 2048-sector boundaries  
> Total free space is 41328573 sectors (19.7 GiB)  
> Number Start (sector) End (sector) Size Code Name  
> 1 616448 1230847 300.0 MiB 8300 Linux filesystem  
> Command (? for help): w \#保存分区表  
> Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING  
> PARTITIONS!!  
> Do you want to proceed? (Y/N): y \#输入y进行确认  
> OK; writing new GUID partition table (GPT) to /dev/sdc.  
> The operation has completed successfully.

**例5：将创建的分区表，删除**

> \[root@xuegod140 ~\]\# 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.  
> 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: 0x0000216c  
> Device Boot Start End Blocks Id System  
> /dev/sdb1 2048 616447 307200 83 Linux  
> /dev/sdb2 616448 21587967 10485760 5 Extended  
> /dev/sdb5 618496 1232895 307200 83 Linux  
> Command (m for help): d \#删除分区表  
> Partition number (1,2,5, default 5): 5 \#指定需要删除分区的分区号  
> Partition 5 is deleted  
> 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: 0x0000216c  
> Device Boot Start End Blocks Id System  
> /dev/sdb1 2048 616447 307200 83 Linux  
> /dev/sdb2 616448 21587967 10485760 5 Extended  
> Command (m for help): w \#保存退出  
> The partition table has been altered!  
> Calling ioctl() to re-read partition table.  
> Syncing disks.

3、磁盘分区后，进行格式、挂载  
磁盘挂载有两种方式：  
临时挂载和永久挂载  
永久挂载里面可以直接针对设备的名称，也可以针对设备的UUID挂载，我们一般最好使用设备的UUID挂载，这样如果设备热插拔之后，设备名称会变更，但是UUID不会变动。（格式化分区除外）  
**例1：对创建的分区进行格式**

> \[root@xuegod140 ~\]\# mkfs.xfs /dev/sdb1  
> mkfs.xfs: /dev/sdb1 appears to contain an existing filesystem (swap).  
> mkfs.xfs: Use the -f option to force overwrite.  
> \[root@xuegod140 ~\]\# mkfs.xfs -f /dev/sdb1 \#如果不是新硬盘，需要加-f参数，强制格式化  
> meta-data=/dev/sdb1 isize=512 agcount=4, agsize=19200 blks  
> = sectsz=512 attr=2, projid32bit=1  
> = crc=1 finobt=0, sparse=0  
> data = bsize=4096 blocks=76800, imaxpct=25  
> = sunit=0 swidth=0 blks  
> naming =version 2 bsize=4096 ascii-ci=0 ftype=1  
> log =internal log bsize=4096 blocks=855, version=2  
> = sectsz=512 sunit=0 blks, lazy-count=1  
> realtime =none extsz=4096 blocks=0, rtextents=0

**例2：创建挂载点，挂载分区**

> \[root@xuegod140 ~\]\# mkdir /sdb1  
> \[root@xuegod140 ~\]\# mount /dev/sdb1 /sdb1/  
> \[root@xuegod140 ~\]\# lsblk  
> NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT  
> sda 8:0 0 20G 0 disk  
> ├─sda1 8:1 0 500M 0 part /boot  
> ├─sda2 8:2 0 10G 0 part /  
> └─sda3 8:3 0 4G 0 part \[SWAP\]  
> sdb 8:16 0 20G 0 disk  
> ├─sdb1 8:17 0 300M 0 part /sdb1  
> └─sdb2 8:18 0 1K 0 part  
> sdc 8:32 0 20G 0 disk  
> └─sdc1 8:33 0 300M 0 part  
> sr0 11:0 1 4.2G 0 rom /mnt

上面的挂载方式属于临时挂载，重启后挂在无效

**例3：将挂在内容写入到配置文件，开机自动挂载**

> \[root@xuegod140 mnt\]\# blkid \#查看设备的UUID值  
> /dev/sr0: UUID=“2018-05-03-20-55-23-00” LABEL=“CentOS 7 x86\_64” TYPE=“iso9660” PTTYPE=“dos”  
> /dev/sdb1: UUID=“633c9e4e-04d9-424e-930b-5d01255706c4” TYPE=“xfs”  
> /dev/sda1: UUID=“d7fee807-b89e-4a72-8a36-b75f0890c843” TYPE=“xfs”  
> /dev/sda2: UUID=“2ea34aff-f003-43fc-b512-07f12d8cc644” TYPE=“xfs”  
> /dev/sda3: UUID=“5370fb36-3120-464e-a007-27d0b87d174b” TYPE=“swap”  
> /dev/sdc1: PARTLABEL=“Linux filesystem” PARTUUID=“04f9ff08-385a-483f-953a-38bf1b8b0ba1”  
> \[root@xuegod140 ~\]\# echo “/dev/sdb1 /sdb1 xfs defaults 0 0” >> /etc/fstab  
> \[root@xuegod140 ~\]\# mount -a  
> \[root@xuegod140 ~\]\# tail -1 /etc/fstab  
> /dev/sdb1 /sdb1 xfs defaults 0 0

**例4：使用UUID，挂载分区**

> \[root@xuegod140 ~\]\# echo “UUID=633c9e4e-04d9-424e-930b-5d01255706c4 /sdb1 xfs 0 0” >> /etc/fstab  
> \[root@xuegod140 ~\]\# mount -a  
> \[root@xuegod140 ~\]\# tail -1 /etc/fstab  
> UUID=633c9e4e-04d9-424e-930b-5d01255706c4 /sdb1 xfs 0 0

**例5：卸载分区**  
我们卸载分区的时候有时候也会出现问题，一般情况下都是因为有人在使用我们的挂载目录，所以导致无法卸载。  
可以通过lsof和fuser命令查看是那个用户和进程在使用，直接kill掉。或者强制卸载分区

> \[root@xuegod140 ~\]\# cd /mnt  
> \[root@xuegod140 mnt\]\# umount -a  
> umount: /mnt: target is busy.  
> (In some cases useful info about processes that use  
> the device is found by lsof(8) or fuser(1))  
> \[root@xuegod140 mnt\]\# lsof /mnt  
> COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME  
> bash 1704 root cwd DIR 11,0 2048 1856 /mnt  
> lsof 3148 root cwd DIR 11,0 2048 1856 /mnt  
> lsof 3149 root cwd DIR 11,0 2048 1856 /mnt  
> \[root@xuegod140 mnt\]\# kill -9 1704 \#这里因为是当面终端在占用，所以kill之后，会断开回话

另外一种方法，使用umount强制卸载：

> \[root@xuegod140 ~\]\# cd /mnt  
> \[root@xuegod140 mnt\]\# umount -a  
> umount: /mnt: target is busy.  
> (In some cases useful info about processes that use  
> the device is found by lsof(8) or fuser(1))  
> \[root@xuegod140 mnt\]\# umount -lf /mnt  
> \[root@xuegod140 mnt\]\# lsblk  
> NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT  
> sda 8:0 0 20G 0 disk  
> ├─sda1 8:1 0 500M 0 part  
> ├─sda2 8:2 0 10G 0 part /  
> └─sda3 8:3 0 4G 0 part \[SWAP\]  
> sdb 8:16 0 20G 0 disk  
> ├─sdb1 8:17 0 300M 0 part  
> └─sdb2 8:18 0 1K 0 part  
> sdc 8:32 0 20G 0 disk  
> └─sdc1 8:33 0 300M 0 part  
> sr0 11:0 1 4.2G 0 rom

扩展了解：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MTg0MzY5OQ_size_16_color_FFFFFF_t_70]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MTg0MzY5OQ_size_16_color_FFFFFF_t_70 1]

# 磁盘分区免交互方法 #

方法一：使用脚本分区

> \[root@xuegod140 ~\]\# vim [a.sh][]  
> \[root@xuegod140 ~\]\# cat [a.sh][]  
> \#!/bin/bash  
> fdisk /dev/sdb << EOF  
> n  
> l  
> \#空格起来，表示默认  
> \+300M  
> w  
> EOF  
> \[root@xuegod140 ~\]\# . [a.sh][]  
> 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.  
> Command (m for help): Partition type:  
> p primary (1 primary, 1 extended, 2 free)  
> l logical (numbered from 5)  
> Select (default p): Adding logical partition 6  
> First sector (1234944-21587967, default 1234944): Using default value 1234944  
> Last sector, +sectors or +size\{K,M,G\} (1234944-21587967, default 21587967): Partition 6 of type Linux and of size 300 MiB is set  
> Command (m for help): The partition table has been altered!  
> Calling ioctl() to re-read partition table.  
> Syncing disks.  
> \[root@xuegod140 ~\]\# lsblk  
> NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT  
> sda 8:0 0 20G 0 disk  
> ├─sda1 8:1 0 500M 0 part /boot  
> ├─sda2 8:2 0 10G 0 part /  
> └─sda3 8:3 0 4G 0 part \[SWAP\]  
> sdb 8:16 0 20G 0 disk  
> ├─sdb1 8:17 0 300M 0 part  
> ├─sdb2 8:18 0 1K 0 part  
> ├─sdb5 8:21 0 300M 0 part  
> └─sdb6 8:22 0 300M 0 part \#自动创建一个sdb6  
> sdc 8:32 0 20G 0 disk  
> └─sdc1 8:33 0 300M 0 part  
> sr0 11:0 1 4.2G 0 rom /mnt

方法二：

> \[root@xuegod140 ~\]\# echo -e “n\\nl\\n\\n+300M\\nw\\n” | 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.  
> Command (m for help): Partition type:  
> p primary (1 primary, 1 extended, 2 free)  
> l logical (numbered from 5)  
> Select (default p): Adding logical partition 7  
> First sector (1851392-21587967, default 1851392): Using default value 1851392  
> Last sector, +sectors or +size\{K,M,G\} (1851392-21587967, default 21587967): Partition 7 of type Linux and of size 300 MiB is set  
> Command (m for help): The partition table has been altered!  
> Calling ioctl() to re-read partition table.  
> Syncing disks.  
> \[root@xuegod140 ~\]\# lsblk  
> NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT  
> sda 8:0 0 20G 0 disk  
> ├─sda1 8:1 0 500M 0 part /boot  
> ├─sda2 8:2 0 10G 0 part /  
> └─sda3 8:3 0 4G 0 part \[SWAP\]  
> sdb 8:16 0 20G 0 disk  
> ├─sdb1 8:17 0 300M 0 part  
> ├─sdb2 8:18 0 1K 0 part  
> ├─sdb5 8:21 0 300M 0 part  
> ├─sdb6 8:22 0 300M 0 part  
> └─sdb7 8:23 0 300M 0 part  
> sdc 8:32 0 20G 0 disk  
> └─sdc1 8:33 0 300M 0 part  
> sr0 11:0 1 4.2G 0 rom /mnt

# 扩展swap分区 #

这里说明两种方式  
方法一：使用磁盘分区扩展swap大小  
**1）将已经划分好的分区，转为为swap类型**

> \[root@xuegod140 ~\]\# 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.  
> 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: 0x0000216c  
> Device Boot Start End Blocks Id System  
> /dev/sdb1 2048 616447 307200 83 Linux  
> /dev/sdb2 616448 21587967 10485760 5 Extended  
> /dev/sdb5 618496 1232895 307200 83 Linux  
> Command (m for help): t \#转换格式  
> Partition number (1,2,5, default 5): 5 \#将分号为5的分区转换分区类型  
> Hex code (type L to list all codes): l \#查看支持的列表  
> Hex code (type L to list all codes): 82 \#转换为Linux swap类型  
> Changed type of partition ‘Linux’ to ‘Linux swap / Solaris’  
> 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: 0x0000216c  
> Device Boot Start End Blocks Id System  
> /dev/sdb1 2048 616447 307200 83 Linux  
> /dev/sdb2 616448 21587967 10485760 5 Extended  
> /dev/sdb5 618496 1232895 307200 82 Linux swap / Solaris  
> Command (m for help): w \#保存  
> The partition table has been altered!  
> Calling ioctl() to re-read partition table.  
> Syncing disks.

**2）格式分区，将分区格式为swap类型**

> \[root@xuegod140 ~\]\# mkswap /dev/sdb5  
> Setting up swapspace version 1, size = 307196 KiB  
> no label, UUID=a1cc60d2-9873-4255-a7ed-70ffeaf1f9f7  
> \[root@xuegod140 ~\]\# blkid  
> /dev/sr0: UUID=“2018-05-03-20-55-23-00” LABEL=“CentOS 7 x86\_64” TYPE=“iso9660” PTTYPE=“dos”  
> /dev/sdb1: UUID=“633c9e4e-04d9-424e-930b-5d01255706c4” TYPE=“xfs”  
> /dev/sda1: UUID=“d7fee807-b89e-4a72-8a36-b75f0890c843” TYPE=“xfs”  
> /dev/sda2: UUID=“2ea34aff-f003-43fc-b512-07f12d8cc644” TYPE=“xfs”  
> /dev/sda3: UUID=“5370fb36-3120-464e-a007-27d0b87d174b” TYPE=“swap”  
> /dev/sdc1: PARTLABEL=“Linux filesystem” PARTUUID=“04f9ff08-385a-483f-953a-38bf1b8b0ba1”  
> /dev/sdb5: UUID=“a1cc60d2-9873-4255-a7ed-70ffeaf1f9f7” TYPE=“swap”

**3）查看swap的大小，并开启swap分区**

> \[root@xuegod140 ~\]\# free -m  
> total used free shared buff/cache available  
> Mem: 3934 391 3190 20 352 3260  
> Swap: 4095 0 4095  
> \[root@xuegod140 ~\]\# swapon /dev/sdb5  
> \[root@xuegod140 ~\]\# free -m  
> total used free shared buff/cache available  
> Mem: 3934 391 3190 20 352 3260  
> Swap: 4395 0 4395

**4）关闭swap分区**

> \[root@xuegod140 ~\]\# swapoff /dev/sdb5  
> \[root@xuegod140 ~\]\# free -m  
> total used free shared buff/cache available  
> Mem: 3934 391 3189 20 352 3259  
> Swap: 4095 0 4095

方法二：使用dd命令，生成一个300M的空间

> \[root@xuegod140 ~\]\# dd if=/dev/zero of=swapfile bs=30M count=10  
> 10+0 records in  
> 10+0 records out  
> 314572800 bytes (315 MB) copied, 3.76789 s, 83.5 MB/s  
> \[root@xuegod140 ~\]\# ll -h swapfile  
> \-rw-r–r-- 1 root root 300M Apr 10 00:35 swapfile  
> \[root@xuegod140 ~\]\# chmod 0600 swapfile  
> \[root@xuegod140 ~\]\# mkswap swapfile  
> Setting up swapspace version 1, size = 307196 KiB  
> no label, UUID=e7a6595f-1909-422b-9fd0-32c95e052ff2  
> \[root@xuegod140 ~\]\# free -m  
> total used free shared buff/cache available  
> Mem: 3934 392 2880 20 661 3255  
> Swap: 4095 0 4095  
> \[root@xuegod140 ~\]\# swapon /root/swapfile  
> \[root@xuegod140 ~\]\# swapon /root/swapfile  
> \[root@xuegod140 ~\]\# free -m  
> total used free shared buff/cache available  
> Mem: 3934 391 2881 20 661 3255  
> Swap: 4395 0 4395  
> \[root@xuegod140 ~\]\# swapoff /root/swapfile  
> \[root@xuegod140 ~\]\# free -m  
> total used free shared buff/cache available  
> Mem: 3934 391 2881 20 661 3255  
> Swap: 4095 0 4095

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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MTg0MzY5OQ_size_16_color_FFFFFF_t_70 1]: /images/20220222/ff3570d620504d1381b4b8d90fd5fdad.png
[a.sh]: http://a.sh