Linux Learning-Bird Brother-Chapter 8-Compression of Files and File Systems

1. Common compression commands in Linux systems

Common compressed file extensions of Linux systems:

  `*.Z`		`compress`程序压缩的文件
  `*.zip`	`zip`程序压缩的文件
  `*.gz`	`gzip`程序压缩的文件
  `.bz2`	`bzip2`程序压缩的文件
  `.xz`		`xz`程序压缩的文件
  `*.tar`	`tar`程序打包的文件，并且没有被压缩过
  `.tar.gz`	`tar`程序打包的文件，并且经过`gzip2`的压缩
  `.tar.bz2``tar`程序打包的文件，并且经过`bzip2`的压缩
  `.tar.xz`	`tar`程序打包的文件，并且经过`xz`的压缩

Linux is the most common compression command gzip, bzipand the latest xz, while others have been out of fashion.
tarMany files can be packaged as a file, but it does not have a compression function. In the GUN plan, the whole tarand compression functions are combined to provide users with powerful compression and packaging functions.
The following introduces these basic compression commands

1.gzip、zcat、zmore、zless、zgrep

gzipThe compressed file created is *.gz, let's take a look at the usage of this command

  gzip [-cdtv] 文件名
  zcat 文件名.gz
#选项与参数
  -c:将压缩的数据输出到屏幕上，可通过数据流重定向来处理
  -d:解压缩的参数
  -t:可以用来检验一个压缩文件的一致性，看看文件是否有误
  -v:可以显示出原文件/压缩文件的压缩比等信息
  -#:#为数字的意思，-1最快，-9最慢，但是压缩比最好，默认是-6

Example 1: Find /etcthe file with the largest capacity below (without subdirectories), copy it /tmp, and then gzipcompress it
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When using gzipcompression, the original file will be compressed as a .gzsuffix by default , and the source file will no longer exist.
Example 2: Because it servicesis a text file, you can read the contents of the previous compressed file

  #`zcat`,`zmore`，`zless`可以读取文本文件
  zcat services.gz

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2.bzip2、bzcat、bzmore、bzless、bzgrep

bzip2The usage is the gzipsame, except that the extension has been .gzchanged to .bz2provide the best compression ratio

3.xz、xzcat、xzmore、xzless、xzgrep

xzHigher compression ratio

`xz` 	[-dtlkc#] 文件名
`xcat`	文件名.xz
#选项与参数
-d	解压缩
-t	测试压缩文件的完整性
-l	列出压缩文件的相关信息
-k	保留原本的文件不删除
-c	将数据在屏幕上输出
-#	压缩比参数
xz -l services.xz #列出压缩前后的容量
xz -d services.xz #解压缩
xz -k services #保留原文件的文件名，并进一步压缩文件

Remarks : When I first started using the xzcommand, I found that this command was not installed, so it was installed again, and the system did not bring the xzcommand

Second, the packaging command: tar

tarYou can package multiple directories or files in the Linux system into one large file. Can also gzip, bzip2, xzsupport, compress the files at the same time.

  tar [-z|-j|-J] [cv] [-f 待建立的新文件名] filename...  <==打包与压缩
  tar [-z|-j|-J] [tv] [-f 既有的tar文件名]			  <===查看文件名
  tar [-z|-j|-J] [xv] [-f 既有的tar文件名] [-C 目录]	 <===解压缩
  #选项与参数
  -c: 建立打包文件，可以搭配-v来查看打包过程中的文件名(filename)
  -t: 查看打包文件的内容包含哪些文件，重点在查看[文件名]
  -x: 解包或解压缩的功能，可以搭配-C（大写）在特定目录解压
  -z: 通过`gzip`的支持进行压缩/解压缩，此文件名最好为*.tar.gz
  -j: 通过`bzip`的支持进行压缩/解压缩，此文件名最好为*.tar.bz2
  -J: 通过`xz`的支持进行压缩/解压缩，此时文件名最好为*.tar.xz。
  
  -v:在压缩/解压缩的过程中，将正在处理的文件名显示处理
  -f filename:-f 后面要立刻接要被处理的文件名
  -C 目录：在特定目录解压，需要这个参数

The simplest use tar:

  压缩：tar -jcv -f filename.tar.bz2 [需要被压缩的文件或目录] 
  查询：tar -jtv -f filename.tar.bz2 
  解压：tar -jxv -f filename.tar.bz2 -C [需要解压的目录]

Let's test a few commonly used tarmethods

• Use the tar-z, -j, -J parameters to back up the /etcdirectory

time tar -jpcv -f /root/etc.tar.bz2 /etc
time tar -jpcv -f /root/etc.tar.bz2 /etc
time tar -Jpcv -f /root/etc.tar.xz /etc

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3. Backup and Restore of XFS File System

Not studying for now

1. XFSFile system backupxfsdump

2. xfsFile system restorexfsrestore

Four, CD writing tools

Not studying for now

5. Other common compression and backup tools

Not studying for now

Six, key review

• The advantage of compression is that it can reduce the waste of disk capacity. On the website, file compression technology can also be used to transfer data, thereby improving the utilization of website bandwidth.
• Extension of the compressed file are *.gzmostly: *.bz2, *.xz, *.tar, *.tar.gz, *.tar.bz2, ,*.tar.xz
• tarCan be used for file packaging, and can support gzip, bzip, xzcompression
• Compression: tar -Jcv -f filename.tar.xz The name of the file or directory to be compressed
• Query: tar -Jtv -f filename.tar.xz
  and can support gzip, bzip, xzcompression
• Compression: tar -Jcv -f filename.tar.xz The name of the file or directory to be compressed
• Query: tar -Jtv ​​-f filename.tar.xz
• Unzip: tar -Jxv -f filename.tar.xz -C need to unzip the directory