檔案的壓縮

1. 壓縮檔案的副檔名
   

   .bz2	bzip2 程式壓縮的檔案；
   .gz	gzip 程式壓縮的檔案；
   .xz	xz 程式壓縮的檔案；
   .tar	tar 程式只打包的資料，沒有壓縮；
   .tar.bz2	tar 程式打包的檔案，且經過 bzip2 壓縮。
   .tar.gz (.tgz)	tar 程式打包的檔案，且經過 gzip 壓縮。
   .tar.xz	tar 程式打包的檔案，且經過 xz 壓縮。

2. 若沒安裝 bzip2，要先安裝。

   [root@kvm8 ~]# dnf install bzip2
   

3. bzip2 輔助說明

   [root@kvm8 ~]# bzip2 --help
   bzip2, a block-sorting file compressor.  Version 1.0.8, 13-Jul-2019.
   
      usage: bzip2 [flags and input files in any order]
   
      -h --help           print this message
      -d --decompress     force decompression
      -z --compress       force compression
      -k --keep           keep (don't delete) input files
      -f --force          overwrite existing output files
      -t --test           test compressed file integrity
      -c --stdout         output to standard out
      -q --quiet          suppress noncritical error messages
      -v --verbose        be verbose (a 2nd -v gives more)
      -L --license        display software version & license
      -V --version        display software version & license
      -s --small          use less memory (at most 2500k)
      -1 .. -9            set block size to 100k .. 900k
      --fast              alias for -1
      --best              alias for -9
   
      If invoked as `bzip2', default action is to compress.
                 as `bunzip2',  default action is to decompress.
                 as `bzcat', default action is to decompress to stdout.
   
      If no file names are given, bzip2 compresses or decompresses
      from standard input to standard output.  You can combine
      short flags, so `-v -4' means the same as -v4 or -4v, &c.
   
   參數： 
   -d    :解壓縮 
   -z    :壓縮
   

4. bzip2 範例

   [root@kvm8 ~]# echo test > test.txt
   [root@kvm8 ~]# ll test.*
   -rw-r--r--. 1 root root 5 Oct 30 15:59 test.txt
   [root@kvm8 ~]# bzip2 -z test.txt
   [root@kvm8 ~]# ll test*
   -rw-r--r--. 1 root root 45 Oct 30 15:59 test.txt.bz2
   [root@kvm8 ~]# bzip2 -d test.txt.bz2
   [root@kvm8 ~]# ll test*
   -rw-r--r--. 1 root root 5 Oct 30 15:59 test.txt
   

5. gzip 輔助說明

   [root@kvm8 ~]# gzip --help
   Usage: gzip [OPTION]... [FILE]...
   Compress or uncompress FILEs (by default, compress FILES in-place).
   
   Mandatory arguments to long options are mandatory for short options too.
   
     -c, --stdout      write on standard output, keep original files unchanged
     -d, --decompress  decompress
     -f, --force       force overwrite of output file and compress links
     -h, --help        give this help
     -k, --keep        keep (don't delete) input files
     -l, --list        list compressed file contents
     -L, --license     display software license
     -n, --no-name     do not save or restore the original name and timestamp
     -N, --name        save or restore the original name and timestamp
     -q, --quiet       suppress all warnings
     -r, --recursive   operate recursively on directories
         --rsyncable   make rsync-friendly archive
     -S, --suffix=SUF  use suffix SUF on compressed files
         --synchronous synchronous output (safer if system crashes, but slower)
     -t, --test        test compressed file integrity
     -v, --verbose     verbose mode
     -V, --version     display version number
     -1, --fast        compress faster
     -9, --best        compress better
   
   With no FILE, or when FILE is -, read standard input.
   
   Report bugs to <bug-gzip@gnu.org>.
   
   參數： 
   -d    :解壓縮 
   -# --fast --best:# 為數字，--fast 是 1 壓縮速度最快；--best 是 9 最佳壓縮比，預設是 6。
   

6. gzip 範例

   [root@kvm8 ~]# gzip test.txt
   [root@kvm8 ~]# ll test*
   -rw-r--r--. 1 root root 34 Oct 30 15:59 test.txt.gz
   [root@kvm8 ~]# gzip -d test.txt
   [root@kvm8 ~]# ll test*
   -rw-r--r--. 1 root root 5 Oct 30 15:59 test.txt