改變檔案權限

1. chmod 輔助說明

   [root@kvm8 ~]# chmod --help
   Usage: chmod [OPTION]... MODE[,MODE]... FILE...
     or:  chmod [OPTION]... OCTAL-MODE FILE...
     or:  chmod [OPTION]... --reference=RFILE FILE...
   Change the mode of each FILE to MODE.
   With --reference, change the mode of each FILE to that of RFILE.
   
     -c, --changes          like verbose but report only when a change is made
     -f, --silent, --quiet  suppress most error messages
     -v, --verbose          output a diagnostic for every file processed
         --dereference      affect the referent of each symbolic link,
                              rather than the symbolic link itself
     -h, --no-dereference   affect each symbolic link, rather than the referent
         --no-preserve-root  do not treat '/' specially (the default)
         --preserve-root    fail to operate recursively on '/'
         --reference=RFILE  use RFILE's mode instead of specifying MODE values.
                            RFILE is always dereferenced if a symbolic link.
     -R, --recursive        change files and directories recursively
   
   The following options modify how a hierarchy is traversed when the -R
   option is also specified.  If more than one is specified, only the final
   one takes effect. '-H' is the default.
   
     -H                     if a command line argument is a symbolic link
                            to a directory, traverse it
     -L                     traverse every symbolic link to a directory
                            encountered
     -P                     do not traverse any symbolic links
   
         --help        display this help and exit
         --version     output version information and exit
   
   Each MODE is of the form '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'.
   
   GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
   Full documentation <https://www.gnu.org/software/coreutils/chmod>
   or available locally via: info '(coreutils) chmod invocation'
   

2. chmod 命令設定

   chmod [ -R ] xyz 檔案或目錄
   chmod [ -R ] u = r 檔案或目錄
                g + w 檔案或目錄
                o - x 檔案或目錄
                a     檔案或目錄
   chmod u=rwx,go=rx 檔案或目錄
   chmod a-x 檔案或目錄
   

   1. xyz 為三組 rwx 屬性數值之加總。
      r : 4
w : 2
x : 1
   2. -rwxr-xr-- 之屬性數值為 754。
   3. 符號類型
      u : user
g : group
o : other
a : all
+ : 加入
- : 除去
= : 設定
3. 例題：若從光碟複製某一目錄 abc （包含次目錄之所有檔案）至硬碟，則目前使用者雖為檔案擁有者，但卻無法修改該檔案，請問如何以簡單的方式，讓使用者可以修改所有檔案？

   chmod u+w -R abc