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linux系统中swap交换分区的配置方法，swap分区简介，swap分区的创建与删除、swap分区的管理维护等。
linux swap交换分区配置
4g以内的物理内存，swap 设置为内存的2倍。
4-8g的物理内存，swap 等于内存大小。 8-64g 的物理内存，swap 设置为8g。 64-256g物理内存，swap 设置为16g。
实际上，系统中交换分区的大小并不取决于物理内存的量，而是取决于系统中内存的负荷，所以在安装系统时要根据具体的业务来设置swap的值。
[root@rhce ~]# cat /proc/sys/vm/swappiness
60
该值默认值是60.
--临时性修改：
[root@rhce ~]# sysctl vm.swappiness=10 vm.swappiness = 10 [root@rhce ~]# cat /proc/sys/vm/swappiness 10
这里修改已经生效，但是如果重启了系统，又会变成60.
vm.swappiness=10
或者： [root@rhce ~]# echo 'vm.swappiness=10' >>/etc/sysctl.conf
保存，重启，就生效了。
[root@dave ~]# free -m
total used free shared buffers cached Mem: 1954 1923 31 0 21 1345 -/+ buffers/cache: 555 1399 Swap: 1999 21 1978
2.2 释放SWAP 空间
[root@dave ~]# vmstat 1 5
procs -----------memory---------- ---swap-------io---- --system-- -----cpu----- r b swpd free buff cache si so bi bo in cs us sy id wa st 0 0 22272 32620 22032 1378312 0 0 33 38 0 41 1 2 96 0 0 0 0 22272 32612 22032 1378340 0 0 0 0 902 1627 0 5 95 0 0 0 0 22272 32612 22032 1378340 0 0 0 0 905 1636 1 8 91 0 0 0 0 22272 32612 22032 1378340 0 0 0 32 907 1616 0 6 94 0 0 0 0 22272 32612 22032 1378340 0 0 0 0 924 1651 0 8 92 0 0 [root@dave ~]# [root@dave ~]# free -m total used free shared buffers cached Mem: 1954 1923 31 0 21 1345 -/+ buffers/cache: 555 1399 Swap: 1999 21 1978
注意：free命令默认单位为k, -m 单位为M。 我们这里的swap使用了21M的空间。
--查看当前swap 的使用
[root@dave ~]# swapon -s Filename Type Size Used Priority /dev/sda2 partition 2047992 22272 -1 [root@dave ~]# cat /proc/swaps Filename Type Size Used Priority /dev/sda2 partition 2047992 22272 -1 [root@dave ~]#
swapon –s 等于 cat/proc/swaps
--关闭swap 交换分区：
[root@dave ~]# swapoff/dev/sda2 [root@dave ~]# swapon -s Filename Type Size Used Priority --查看swap的使用情况： [root@dave ~]# free -m total used free shared buffers cached Mem: 1954 1939 15 0 21 1343 -/+ buffers/cache: 573 1381 Swap: 0 0 0 --启用swap分区： [root@dave ~]# swapon /dev/sda2 --验证状态： [root@dave ~]# swapon -s Filename Type Size Used Priority /dev/sda2 partition 2047992 0 -1
这里/dev/sda2是我们在安装操作系统时划分的磁盘分区。
[root@dave ~]# swapoff -a
[root@dave ~]# swapon -s Filename Type Size Used Priority [root@dave ~]# swapon -a [root@dave ~]# swapon -s Filename Type Size Used Priority /dev/sda2 partition 2047992 0 -1 [root@dave ~]#
查看/etc/fstab 文件，我们的swap 也配置到开启自动启动了。
[root@dave ~]# cat /etc/fstab
# # /etc/fstab # Created by anaconda on Wed Aug 15 00:09:26 2012 # # Accessible filesystems, by reference, aremaintained under '/dev/disk' # See man pages fstab(5), findfs(8), mount(8)and/or blkid(8) for more info # UUID=beea0820-3ac3-4551-9bf0-1b2a462d3ab4 / ext4 defaults 1 1 UUID=e5ec9543-143f-4e3b-b8a7-4fa05b01836a/boot ext4 defaults 1 2 UUID=b256c0bb-9000-456b-b9eb-18239b5df5ddswap swap defaults 0 0 tmpfs /dev/shm tmpfs defaults 0 0 devpts /dev/pts devpts gid=5,mode=620 0 0 sysfs /sys sysfs defaults 0 0 proc /proc proc defaults 0 0
简单说明：
--在根目录下生成一个文件：swap-file，大小1G：
[root@dave u01]# dd if=/dev/zero of=/swap-filebs=1M count=1024 1024+0 records in 1024+0 records out 1073741824 bytes (1.1 GB) copied, 5.91518 s, 182MB/s [root@dave u01]# cd / [root@dave /]# ls bin cgroup etc lib lost+found misc net proc sbin srv sys u01 usr boot dev home lib64 media mnt opt root selinux swap-file tmp u02 var [root@dave /]# --将生成的文件格式化成交换分区： [root@dave /]# mkswap /swap-file mkswap: /swap-file: warning: don't erase bootbitssectors onwhole disk. Use -f to force. Setting up swapspace version 1, size = 1048572 KiB no label, UUID=653bbeb5-4abb-4295-b110-5847e073140d --这里没有分区的lable，只有一个UUID。 --启动swap分区并查看状态： [root@dave /]# swapon /swap-file [root@dave /]# swapon -s Filename Type Size Used Priority /dev/sda2 partition 2047992 0 -1 /swap-file file 1048568 0 -2
这里就看到了2个swap。
UUID=653bbeb5-4abb-4295-b110-5847e073140d swap swap defaults 0 0
或者： /swap-file swap swap defaults 0 0
2.4 使用磁盘添加swap
[root@rhce /]# fdisk /dev/sdb
Device contains neither a valid DOS partitiontable, nor Sun, SGI or OSF disklabel Building a new DOS disklabel with disk identifier0x65edb587. Changes will remain in memory only, until youdecide to write them. After that, of course, the previous content won'tbe recoverable. Warning: invalid flag 0x0000 of partition table 4will be corrected by w(rite) WARNING: DOS-compatible mode is deprecated. It'sstrongly recommended to switch off the mode (command 'c') and change display units to sectors (command 'u'). Command (m for help): n Command action e extended p primary partition (1-4) p Partition number (1-4): 1 First cylinder (1-652, default 1): Using default value 1 Last cylinder, +cylinders or +size{K,M,G} (1-652,default 652): +1G Command (m for help): w The partition table has been altered! Calling ioctl() to re-read partition table. Syncing disks. [root@rhce /]# fdisk -l Disk /dev/sda: 21.5 GB, 21474836480 bytes 255 heads, 63 sectors/track, 2610 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x000bcd24 DeviceBoot Start End Blocks Id System /dev/sda1 * 1 128 1024000 83 Linux Partition 1 does not end on cylinder boundary. /dev/sda2 128 511 3072000 82 Linux swap / Solaris Partition 2 does not end on cylinder boundary. /dev/sda3 511 2611 16874496 83 Linux Disk /dev/sdb: 5368 MB, 5368709120 bytes 255 heads, 63 sectors/track, 652 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x65edb587 DeviceBoot Start End Blocks Id System /dev/sdb1 1 132 1060258+ 83 Linux …
注意这里fdisk ID的编号。 这里显示的83，它代表这个分区是ext的分区，这个是不能用来做swap的。
Command (m for help): l
0 Empty 24 NEC DOS 81 Minix / old Lin bf Solaris 1 FAT12 39 Plan 9 82 Linux swap / So c1 DRDOS/sec (FAT- 2 XENIX root 3c PartitionMagic 83 Linux c4 DRDOS/sec (FAT- 3 XENIX usr 40 Venix 80286 84 OS/2 hidden C: c6 DRDOS/sec (FAT- 4 FAT16 <32M 41 PPC PReP Boot 85 Linux extended c7 Syrinx 5 Extended 42 SFS 86 NTFS volume set da Non-FS data 6 FAT16 4d QNX4.x 87 NTFS volume set db CP/M / CTOS / . 7 HPFS/NTFS 4e QNX4.x 2nd part 88 Linuxplaintext de Dell Utility 8 AIX 4f QNX4.x 3rd part 8e Linux LVM df BootIt 9 AIX bootable 50 OnTrack DM 93 Amoeba e1 DOS access a OS/2 Boot Manag 51 OnTrack DM6 Aux 94 Amoeba BBT e3 DOS R/O b W95 FAT32 52 CP/M 9f BSD/OS e4 SpeedStor c W95 FAT32 (LBA) 53 OnTrack DM6 Aux a0 IBM Thinkpad hi eb BeOS fs e W95 FAT16 (LBA) 54 OnTrackDM6 a5 FreeBSD ee GPT f W95 Ext'd (LBA) 55 EZ-Drive a6 OpenBSD ef EFI (FAT-12/16/ 10 OPUS 56 Golden Bow a7 NeXTSTEP f0 Linux/PA-RISC b 11 HiddenFAT12 5c Priam Edisk a8 Darwin UFS f1 SpeedStor 12 Compaqdiagnost 61 SpeedStor a9 NetBSD f4 SpeedStor 14 HiddenFAT16 <3 63 GNU HURD or Sys ab Darwin boot f2 DOS secondary 16 HiddenFAT16 64 Novell Netware af HFS/ HFS+ fb VMware VMFS 17 HiddenHPFS/NTF 65 Novell Netware b7 BSDI fs fc VMware VMKCORE 18 ASTSmartSleep 70 DiskSecure Mult b8 BSDI swap fd Linux raid auto 1b HiddenW95 FAT3 75 PC/IX bb Boot Wizard hid fe LANstep 1c HiddenW95 FAT3 80 Old Minix be Solaris boot ff BBT 1e HiddenW95 FAT1
ext的分区ID号：0x83
[root@rhce ~]# fdisk /dev/sdb
WARNING: DOS-compatible mode is deprecated. It'sstrongly recommended to switch off the mode (command 'c') and change display units to sectors (command 'u'). Command (m for help): h h: unknown command Command action a toggle a bootable flag b edit bsd disklabel c toggle the dos compatibility flag d delete a partition l list known partition types m print this menu n add a new partition o create a new empty DOS partition table p print the partition table 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 x extra functionality (experts only) Command (m for help): t Selected partition 1 Hex code (type L to list codes): L 0 Empty 24 NEC DOS 81 Minix / old Lin bf Solaris 1 FAT12 39 Plan 9 82 Linux swap / So c1 DRDOS/sec (FAT- 2 XENIX root 3c PartitionMagic 83 Linux c4 DRDOS/sec (FAT- 3 XENIX usr 40 Venix 80286 84 OS/2 hidden C: c6 DRDOS/sec (FAT- 4 FAT16 <32M 41 PPC PReP Boot 85 Linux extended c7 Syrinx 5 Extended 42 SFS 86 NTFS volume set da Non-FS data 6 FAT16 4d QNX4.x 87 NTFS volume set db CP/M / CTOS /. 7 HPFS/NTFS 4e QNX4.x 2nd part 88 Linuxplaintext de Dell Utility 8 AIX 4f QNX4.x 3rd part 8e Linux LVM df BootIt 9 AIX bootable 50 OnTrack DM 93 Amoeba e1 DOS access a OS/2 Boot Manag 51 OnTrack DM6 Aux 94 Amoeba BBT e3 DOS R/O b W95 FAT32 52 CP/M 9f BSD/OS e4 SpeedStor c W95 FAT32 (LBA) 53 OnTrack DM6 Aux a0 IBM Thinkpad hi eb BeOS fs e W95 FAT16 (LBA) 54 OnTrackDM6 a5 FreeBSD ee GPT f W95 Ext'd (LBA) 55 EZ-Drive a6 OpenBSD ef EFI (FAT-12/16/ 10 OPUS 56 Golden Bow a7 NeXTSTEP f0 Linux/PA-RISC b 11 HiddenFAT12 5c Priam Edisk a8 Darwin UFS f1 SpeedStor 12 Compaqdiagnost 61 SpeedStor a9 NetBSD f4 SpeedStor 14 HiddenFAT16 <3 63 GNU HURD or Sys ab Darwin boot f2 DOS secondary 16 HiddenFAT16 64 Novell Netware af HFS/ HFS+ fb VMware VMFS 17 HiddenHPFS/NTF 65 Novell Netware b7 BSDI fs fc VMware VMKCORE 18 ASTSmartSleep 70 DiskSecure Mult b8 BSDI swap fd Linux raid auto 1b HiddenW95 FAT3 75 PC/IX bb Boot Wizard hid fe LANstep 1c HiddenW95 FAT3 80 Old Minix be Solaris boot ff BBT 1e HiddenW95 FAT1 Hex code (type L to list codes):82 Changed system type of partition1 to 82 (Linux swap / Solaris) --注意这里更改磁盘分区的ID类型，如果不更在，在系统重启时会根据ID来判断磁盘的类型，那样在使用时就会出现错误。 Command (m for help): w The partition table has been altered! Calling ioctl() to re-read partition table. WARNING: Re-reading the partition table failed witherror 16: Device or resource busy. The kernel still uses the old table. The new tablewill be used at the next reboot or after you run partprobe(8) orkpartx(8) Syncing disks. [root@rhce ~]# --格式化swap分区： [root@rhce /]# mkswap /dev/sdb1 Setting up swapspace version 1, size = 1060252 KiB no label, UUID= bc913e6b-209a-49a7-b561-9b8c57294681 [root@rhce /]# mkswap –L swap-disk/dev/sdc1
一个设置了Lable，一个没设置。我们在添加/etc/fstab时，可是用LABLE名称，或者使用UUID来配置。 具体如上。
Disk /dev/sdb: 5368 MB, 5368709120 bytes
255 heads, 63 sectors/track, 652 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x65edb587 DeviceBoot Start End Blocks Id System /dev/sdb1 1 132 1060258+ 82 Linux swap / Solaris Disk /dev/sdc: 5368 MB, 5368709120 bytes 181 heads, 40 sectors/track, 1448 cylinders Units = cylinders of 7240 * 512 = 3706880 bytes Sector size (logical/physical): 512 bytes / 512bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 DeviceBoot Start End Blocks Id System /dev/sdc1 1 291 1053400 82 Linux swap / Solaris
注意： 使用blkid 查看类型已经变成了swap：
[root@rhce ~]# blkid
/dev/sda1: UUID="935f7fb2-2ef4-486f-ae4e-265eaf9f580f"TYPE="ext4" /dev/sda2:UUID="43343402-9188-4cdc-9c79-0e36ab737517" TYPE="swap" /dev/sda3:UUID="7e49fb2c-6fd8-461a-95d9-65d1f3994160" TYPE="ext4" /dev/sdb1:UUID="bc913e6b-209a-49a7-b561-9b8c57294681" TYPE="swap" /dev/sdc1:LABEL="swap-disk"UUID="799b4379-ca59-4508-ad04-2d18847b3fd9" TYPE="swap" [root@rhce ~]#
这里类型已改变，可以尝试手工的启动swap：
[root@rhce ~]# swapon /dev/sdc1
[root@rhce ~]# swapon -s Filename Type Size Used Priority /dev/sda2 partition 3071992 0 -1 /dev/sdb1 partition 1060248 0 -2 /dev/sdc1 partition 1053392 0 -3
这里可以直接启用swap。
添加内容：
UUID=bc913e6b-209a-49a7-b561-9b8c57294681 swap swap defaults 0 0
LABEL=swap-disk swap swap defaults 0 0
重启系统后查看：
[root@rhce ~]# swapon -s
Filename Type Size Used Priority /dev/sda2 partition 3071992 0 -1 /dev/sdb1 partition 1060248 0 -2 /dev/sdc1 partition 1053392 0 -3 --对/dev/sdb1 进行测试： [root@rhce ~]# swapoff /dev/sdb1 [root@rhce ~]# swapon -s Filename Type Size Used Priority /dev/sda2 partition 3071992 0 -1 [root@rhce ~]# swapon /dev/sdb1 [root@rhce ~]# swapon -s Filename Type Size Used Priority /dev/sda2 partition 3071992 0 -1 /dev/sdb1 partition 1060248 0 -2
2.5 swap 分区的删除 |