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20170625-16 选题
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Automatically Create/Remove And Mount Swap File In Linux Using Shell Script
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============================================================
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Few days ago we have covered an article about swap file creation in Linux using three ways which is the common method but it requires manual human effort.
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Today i have found a small shell script (Two shell script, one for swap file creation and another one for removing swap file) which was written by [Gary Stafford][3] that help us to create/remove & mount swap file automatically in Linux.
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By default the script create and mount `512MB` swapfile. If you want more swap space and different file name you have to modify the script accordingly. It’s not a big deal to modify the script since it’s very handy and small script, even though i have colored the line where you want to modify the script.
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**Suggested Read : **[3 Easy Ways To Create Or Extend Swap Space In Linux][4]
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#### How to check current swap size
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Lets first check the size of existing swap space partition using **[free][1]** & `swapon` command.
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```
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$ free -h
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total used free shared buff/cache available
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Mem: 2.0G 1.3G 139M 45M 483M 426M
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Swap: 2.0G 655M 1.4G
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$ swapon --show
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NAME TYPE SIZE USED PRIO
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/dev/sda5 partition 2G 655.2M -1
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```
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The above output clearly shows `2GB` is my current swap space.
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#### Create Swap File
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Create `create_swap.sh` file and add below script to automate the swap space creation and mounting.
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```
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$ nano create_swap.sh
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#!/bin/sh
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# size of swapfile in megabytes
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swapsize=1024
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# does the swap file already exist?
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grep -q "swapfile" /etc/fstab
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# if not then create it
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if [ $? -ne 0 ]; then
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echo 'swapfile not found. Adding swapfile.'
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fallocate -l ${swapsize}M /swapfile
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chmod 600 /swapfile
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mkswap /swapfile
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swapon /swapfile
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echo '/swapfile none swap defaults 0 0' >> /etc/fstab
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else
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echo 'swapfile found. No changes made.'
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fi
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echo '--------------------------------------------'
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echo 'Check whether the swap space created or not?'
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echo '--------------------------------------------'
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swapon --show
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```
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Add execute permission to the file.
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```
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$ sudo +x create_swap.sh
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```
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Run the file to create and mount swap file.
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```
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$ sudo ./create_swap.sh
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swapfile not found. Adding swapfile.
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Setting up swapspace version 1, size = 1024 MiB (1073737728 bytes)
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no label, UUID=d9004261-396a-4321-a45f-9923e3e1328c
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--------------------------------------------
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Check whether the swap space created or not?
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--------------------------------------------
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NAME TYPE SIZE USED PRIO
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/dev/sda5 partition 2G 954.1M -1
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/swapfile file 1024M 0B -2
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```
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Yes i can see the new `1024M swapfile`. Reboot the system to use the new swap file.
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#### Remove Swap File
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If the swap file is no longer required, then create `remove_swap.sh` file and add below script to remove swap file and its mount point from /etc/fstab.
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```
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$ nano remove_swap.sh
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#!/bin/sh
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# does the swap file exist?
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grep -q "swapfile" /etc/fstab
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# if it does then remove it
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if [ $? -eq 0 ]; then
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echo 'swapfile found. Removing swapfile.'
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sed -i '/swapfile/d' /etc/fstab
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echo "3" > /proc/sys/vm/drop_caches
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swapoff -a
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rm -f /swapfile
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else
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echo 'No swapfile found. No changes made.'
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fi
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echo '--------------------------------------------'
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echo 'Check whether the swap space removed or not?'
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echo '--------------------------------------------'
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swapon --show
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```
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Add execute permission to the file.
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```
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$ sudo +x remove_swap.sh
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```
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Run the file to remve and unmount swap file.
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```
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$ sudo ./remove_swap.sh
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swapfile found. Removing swapfile.
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swapoff: /dev/sda5: swapoff failed: Cannot allocate memory
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--------------------------------------------
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Check whether the swap space removed or not?
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--------------------------------------------
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NAME TYPE SIZE USED PRIO
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/dev/sda5 partition 2G 951.8M -1
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```
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<nav class="pagination group" style="display: block; margin: 0px 0px 15px; padding: 0px; border: 0px; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; font-size: inherit; line-height: inherit; font-family: inherit; vertical-align: baseline; zoom: 1;"></nav>
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--------------------------------------------------------------------------------
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via: http://www.2daygeek.com/shell-script-create-add-extend-swap-space-linux/
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作者：[2DAYGEEK ][a]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]:http://www.2daygeek.com/author/2daygeek/
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[1]:http://www.2daygeek.com/free-command-to-check-memory-usage-statistics-in-linux/
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[2]:http://www.2daygeek.com/author/2daygeek/
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[3]:https://programmaticponderings.com/2013/12/19/scripting-linux-swap-space/
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[4]:http://www.2daygeek.com/add-extend-increase-swap-space-memory-file-partition-linux/
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