swapon 命令详解

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swapon 命令启用设备或文件进行交换。

swapon 命令安装：

-bash/zsh: swapon command not found

#Debian
apt-get install mount

#Ubuntu
apt-get install mount

#Alpine
apk add util-linux

#Arch Linux
pacman -S util-linux

#Kali Linux
apt-get install mount

#CentOS
yum install util-linux

#Fedora
dnf install util-linux

#OS X
brew install util-linux

#Raspbian
apt-get install loop-aes-utils

#Docker
docker run cmd.cat/swapon swapon

swapon 命令补充说明：

swapon 命令用于激活 Linux 系统中交换空间，Linux 系统的内存管理必须使用交换区来建立虚拟内存。

swapon 命令语法：

swapon [options] [specialfile...]

--------------------------------
To get swap information:
swapon -s [-h] [-V]

To enable a swap area:
swapon [-d] [-f] [-p priority] [-v] specialfile...

To disable a swap area:
swapoff [-v] specialfile...

To enable all swap areas:
swapon -a [-e] [-f] [-v]

To disable all swap areas:
swapoff -a [-v]

swapon 命令选项：

-a, --all
      All devices marked as ``swap'' in /etc/fstab are made
      available, except for those with the ``noauto'' option.
      Devices that are already being used as swap are silently
      skipped.

-d, --discard[=policy]
      Enable swap discards, if the swap backing device supports
      the discard or trim operation.  This may improve
      performance on some Solid State Devices, but often it does
      not.  The option allows one to select between two
      available swap discard policies: --discard=once to perform
      a single-time discard operation for the whole swap area at
      swapon; or --discard=pages to asynchronously discard freed
      swap pages before they are available for reuse.  If no
      policy is selected, the default behavior is to enable both
      discard types.  The /etc/fstab mount options discard,
      discard=once, or discard=pages may also be used to enable
      discard flags.

-e, --ifexists
      Silently skip devices that do not exist.  The /etc/fstab
      mount option nofail may also be used to skip non-existing
      device.

-f, --fixpgsz
      Reinitialize (exec mkswap) the swap space if its page size
      does not match that of the current running kernel.
      mkswap(8) initializes the whole device and does not check
      for bad blocks.

-h, --help
      Display help text and exit.

-L label
      Use the partition that has the specified label.  (For
      this, access to /proc/partitions is needed.)

-o, --options opts
      Specify swap options by an fstab-compatible comma-
      separated string.  For example:

             swapon -o pri=1,discard=pages,nofail /dev/sda2

      The opts string is evaluated last and overrides all other
      command line options.

-p, --priority priority
      Specify the priority of the swap device.  priority is a
      value between -1 and 32767.  Higher numbers indicate
      higher priority.  See swapon(2) for a full description of
      swap priorities.  Add pri=value to the option field of
      /etc/fstab for use with swapon -a.  When no priority is
      defined, it defaults to -1.

-s, --summary
      Display swap usage summary by device.  Equivalent to "cat
      /proc/swaps".  This output format is DEPRECATED in favour
      of --show that provides better control on output data.

--show[=column...]
      Display a definable table of swap areas.  See the --help
      output for a list of available columns.

--output-all
      Output all available columns.

--noheadings
      Do not print headings when displaying --show output.

--raw  Display --show output without aligning table columns.

--bytes
      Display swap size in bytes in --show output instead of in
      user-friendly units.

-U uuid
      Use the partition that has the specified uuid.

-v, --verbose
      Be verbose.

-V, --version
      Display version information and exit.