CentOS7 swap partition management (partitions or files)
1, swap can be divided into separate partitions are created when you install the operating system; you can install the operating system into the remaining good drive to create; you can also create a file when using the swap partition
2, it is recommended to create a new partition as swap use, if you want to use a swap partition with a file when it is best to file on solid state hard drive, using the swap file to act as if free to change into small, mobile also convenient, but the performance not as good partition
Create a partition to divide swap
First, the use of free -h to view the current swap
The current system of swap space 4G
[root@centos7 ~]# free -h
total used free shared buff/cache available
Mem: 1.9G 180M 1.2G 19M 545M 1.6G
Swap: 4.0G 12M 4.0GUse swapon -s displays the current system of swap
[root@centos7 ~]# swapon -s
Filename Type Size Used Priority
/dev/dm-0 partition 419430012676 -2Second, the use lsblk view the current hard disk system
You can see, sda total of 200G, now divided into more than 150 G, there may be room for
[root@centos7 ~]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 200G 0 disk
├─sda1 8:1 0 1G 0 part /boot
├─sda2 8:2 0 100G 0 part /
├─sda3 8:3 0 50G 0 part /data
├─sda4 8:4 0 1K 0 part
└─sda5 8:5 0 4G 0 part
└─centos-swap
253:0 0 4G 0 lvm [SWAP]
sdb 8:16 0 20G 0 disk
└─sdb2 8:18 0 2G 0 part Third, the use of fdisk / dev / sda hard disk partition operations created
[root@centos7 ~]# fdisk /dev/sda
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
All primary partitions are in use
Adding logical partition 6
First sector (325072896-419430399, default 325072896):
Using default value 325072896
Last sector, +sectors or +size{K,M,G} (325072896-419430399, default 419430399): +2G
Partition 6 of type Linux and of size 2 GiB is set
Command (m for help): p
Disk /dev/sda: 214.7 GB, 214748364800 bytes, 419430400 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: 0x000f14f7
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 2099199 1048576 83 Linux
/dev/sda2 2099200 211814399 104857600 83 Linux
/dev/sda3 211814400 316671999 52428800 83 Linux
/dev/sda4 316672000 419430399 51379200 5 Extended
/dev/sda5 316674048 325070847 4198400 8e Linux LVM
/dev/sda6 325072896 329267199 2097152 83 Linux
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 with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.Fourth, performed twice partprobe (CentOS6 execution part / dev / sda -a)
[root@centos7 ~]# partprobe
Warning: Unable to open /dev/sr0 read-write (Read-only file system). /dev/sr0 has been opened read-only.
Error: Invalid partition table - recursive partition on /dev/sr0.
Warning: Unable to open /dev/sr1 read-write (Read-only file system). /dev/sr1 has been opened read-only.
[root@centos7 ~]# partprobe
Warning: Unable to open /dev/sr0 read-write (Read-only file system). /dev/sr0 has been opened read-only.
Error: Invalid partition table - recursive partition on /dev/sr0.
Warning: Unable to open /dev/sr1 read-write (Read-only file system). /dev/sr1 has been opened read-only.Fifth, create a file system
[root@centos7 ~]# ls /dev/sda6
/dev/sda6
[root@centos7 ~]# mkswap /dev/sda6
Setting up swapspace version 1, size = 2097148 KiB
no label, UUID=b98996a2-a548-4266-b636-b2cb75cd0626Sixth, the write / etc / fstab , and mount -a test
[root@centos7 ~]# blkid /dev/sda6
/dev/sda6: UUID="b98996a2-a548-4266-b636-b2cb75cd0626" TYPE="swap"
[root@centos7 ~]# vim /etc/fstab
[root@centos7 ~]# tail -1 /etc/fstab
UUID=b98996a2-a548-4266-b636-b2cb75cd0626 swap swap defaults 0 0
# 被挂载的设备名 挂载点 文件系统类型 挂载选项 转储频率 系统自检选项
[root@centos7 ~]# mount -aSeven, swapon -a
Run the free -h, swap partition has not displayed, execute swapon -a, enable all swap
[root@centos7 ~]# free -h
total used free shared buff/cache available
Mem: 1.9G 176M 1.2G 19M 547M 1.6G
Swap: 4.0G 12M 4.0G
# 执行swapon -a
[root@centos7 ~]# swapon -a
[root@centos7 ~]# free -h
total used free shared buff/cache available
Mem: 1.9G 178M 1.2G 19M 547M 1.6G
Swap: 6.0G 12M 6.0GEight, uninstall the swap
# 使用swapoff关闭/dev/sda6这个swap分区
[root@centos7 ~]# swapoff /dev/sda6
# 使用sed删除fstab最后加的一行
[root@centos7 ~]# sed -ri '$d' /etc/fstab
# mount -a
[root@centos7 ~]# mount -a
# 此时swap已变成原来的4GCreate a file acts as a swap partition
First, use the dd command to create a file 100M, when swap with
[root@centos7 data]# dd if=/dev/zero of=/data/swapfile bs=1M count=100
100+0 records in
100+0 records out
104857600 bytes (105 MB) copied, 2.74665 s, 38.2 MB/s
# swap文件权限修改为600，安全
[root@centos7 data]# chmod 600 swapfileSecond, create a file on the file system
[root@centos7 data]# mkswap swapfile
Setting up swapspace version 1, size = 102396 KiB
no label, UUID=a16538e7-685e-4141-aaeb-e1b7896cffdfThird, the write / etc / fstab, mount (Here we note that, mount the device can not write UUID, only write the file name)
[root@centos7 data]# tail -1 /etc/fstab
/data/swapfile swap swap defaults 0 0
[root@centos7 data]# mount -aFourth, the implementation swapon -a Open All swap
[root@centos7 data]# swapon -a
[root@centos7 data]# swapon -s
Filename Type Size Used Priority
/dev/dm-0 partition 4194300 12672 -2
/data/swapfile file 102396 0 -3
[root@centos7 data]# free -h
total used free shared buff/cache available
Mem: 1.9G 176M 1.1G 19M 650M 1.6G
Swap: 4.1G 12M 4.1GFifth, increase the swap, you need to be unmounted
# 必须先卸载，不然报错了
[root@centos7 data]# dd if=/dev/zero of=/data/swapfile bs=1M count=200
dd: failed to open ‘/data/swapfile’: Text file busy
# 卸载
[root@centos7 data]# swapoff /data/swapfile
[root@centos7 data]# dd if=/dev/zero of=/data/swapfile bs=1M count=200
200+0 records in
200+0 records out
209715200 bytes (210 MB) copied, 3.23377 s, 64.9 MB/s
# 创建文件系统
[root@centos7 data]# mkswap swapfile
Setting up swapspace version 1, size = 204796 KiB
no label, UUID=79d0f287-c998-42d3-aabc-b3b2d60b9cb2
# 执行swapon -a启用所有swap
[root@centos7 data]# swapon -a
[root@centos7 data]# free -h
total used free shared buff/cache available
Mem: 1.9G 176M 1.0G 19M 752M 1.6G
Swap: 4.2G 12M 4.2GSixth, uninstall
# 取消挂载
[root@centos7 data]# swapoff /data/swapfile
[root@centos7 data]# sed -ri '$d' /etc/fstab
[root@centos7 data]# mount -a
[root@centos7 data]# rm -f swapfile
[root@centos7 data]# free -h
total used free shared buff/cache available
Mem: 1.9G 176M 1.2G 19M 547M 1.6G
Swap: 4.0G 12M 4.0G