chmod(重要)
- 命令名称:chmod
- 英文原意:change the permissions mode of a file
- 执行权限:所有用户
- 功能描述:改变文件或目录权限
- 语法:chmod [{ugoa}{+-=}{rwxX}] [文件或目录] [mode=421] [文件或目录]
- -R:递归修改
- u 表示该档案的拥有者,g 表示与该档案的拥有者属于同一个群体(group)者,o 表示其他以外的人,a 表示这三者皆是。
-
- 表示增加权限、- 表示取消权限、= 表示唯一设定权限。
- r 表示可读取,w 表示可写入,x 表示可执行,X 表示只有当该档案是个子目录或者该档案已经被设定过为可执行。
- 关于mode,用数字来表示权限
- r —- 4
- w —- 2
- x —- 1
- 所以
rwxrw-r--
对应的是764 - image-20210510190713527
例子1:
<span class="linenum hljs-number">1</span>root@atomy-<span class="hljs-keyword">virtual</span>-machine:/tmp<br><span class="linenum hljs-number">2</span>-rw-r--r-- <span class="hljs-number">1</span> root root <span class="hljs-number">0</span> <span class="hljs-number">5</span>月  <span class="hljs-number">10</span> <span class="hljs-number">18</span>:<span class="hljs-number">53</span> linuxstudy.<span class="hljs-built_in">list</span><br><span class="linenum hljs-number">3</span>root@atomy-<span class="hljs-keyword">virtual</span>-machine:/tmp<br><span class="linenum hljs-number">4</span>root@atomy-<span class="hljs-keyword">virtual</span>-machine:/tmp<br><span class="linenum hljs-number">5</span>-rwxr--r-- <span class="hljs-number">1</span> root root <span class="hljs-number">0</span> <span class="hljs-number">5</span>月  <span class="hljs-number">10</span> <span class="hljs-number">18</span>:<span class="hljs-number">53</span> linuxstudy.<span class="hljs-built_in">list</span>
上述例子中我们用 chmod u+x linuxstudy.list
语句修改了linuxstudy.list文件的权限,其含义是赋予该文件的拥有者执行权限。
例子2:
<span class="linenum hljs-number">1</span>root@atomy-<span class="hljs-keyword">virtual</span>-machine:/tmp<br><span class="linenum hljs-number">2</span>root@atomy-<span class="hljs-keyword">virtual</span>-machine:/tmp<br><span class="linenum hljs-number">3</span>-rwxrw---- <span class="hljs-number">1</span> root root <span class="hljs-number">0</span> <span class="hljs-number">5</span>月  <span class="hljs-number">10</span> <span class="hljs-number">18</span>:<span class="hljs-number">53</span> linuxstudy.<span class="hljs-built_in">list</span>
可以同时修改多个权限,用逗号分隔即可。上述语句令用户组拥有写的权限,去除了其他人读的权限。
例子3:
<span class="linenum hljs-number">1</span>root@atomy-<span class="hljs-keyword">virtual</span>-machine:/tmp<br><span class="linenum hljs-number">2</span>root@atomy-<span class="hljs-keyword">virtual</span>-machine:/tmp<br><span class="linenum hljs-number">3</span>-rwxrwx--- <span class="hljs-number">1</span> root root <span class="hljs-number">0</span> <span class="hljs-number">5</span>月  <span class="hljs-number">10</span> <span class="hljs-number">18</span>:<span class="hljs-number">53</span> linuxstudy.<span class="hljs-built_in">list</span>
我们也可以直接用 =
来赋予权限!
不过,我们在实际操作中用的最多的并不是这种方式,而是用数字来表示。
例子4:
<span class="linenum hljs-number">1</span>root@atomy-<span class="hljs-keyword">virtual</span>-machine:/tmp<br><span class="linenum hljs-number">2</span>root@atomy-<span class="hljs-keyword">virtual</span>-machine:/tmp<br><span class="linenum hljs-number">3</span>-rw-r----- <span class="hljs-number">1</span> root root <span class="hljs-number">0</span> <span class="hljs-number">5</span>月  <span class="hljs-number">10</span> <span class="hljs-number">18</span>:<span class="hljs-number">53</span> linuxstudy.<span class="hljs-built_in">list</span>
640代表要将权限修改为 rw-r-----
例子5:关于-R,递归修改权限的操作
创建一个递归的文件夹,两个文件夹a和b的权限如下:
<span class="linenum hljs-number">1</span>root@atomy-virtual-machine:/tmp<br><span class="linenum hljs-number">2</span>root@atomy-virtual-machine:/tmp<br><span class="linenum hljs-number">3</span>drwxr-xr-x <span class="hljs-number">3</span> root root <span class="hljs-number">4096</span> <span class="hljs-number">5</span>月  <span class="hljs-number">10</span> <span class="hljs-number">19</span>:<span class="hljs-number">12</span> /tmp/a<br><span class="linenum hljs-number">4</span>root@atomy-virtual-machine:/tmp<br><span class="linenum hljs-number">5</span>drwxr-xr-x <span class="hljs-number">2</span> root root <span class="hljs-number">4096</span> <span class="hljs-number">5</span>月  <span class="hljs-number">10</span> <span class="hljs-number">19</span>:<span class="hljs-number">12</span> /tmp/a/b
修改文件夹a的权限,然后查看两者的权限:
<span class="linenum hljs-number">1</span>root@atomy-virtual-machine:/tmp<br><span class="linenum hljs-number">2</span>root@atomy-virtual-machine:/tmp<br><span class="linenum hljs-number">3</span>drwxrwxrwx <span class="hljs-number">3</span> root root <span class="hljs-number">4096</span> <span class="hljs-number">5</span>月  <span class="hljs-number">10</span> <span class="hljs-number">19</span>:<span class="hljs-number">12</span> /tmp/a<br><span class="linenum hljs-number">4</span>root@atomy-virtual-machine:/tmp<br><span class="linenum hljs-number">5</span>drwxr-xr-x <span class="hljs-number">2</span> root root <span class="hljs-number">4096</span> <span class="hljs-number">5</span>月  <span class="hljs-number">10</span> <span class="hljs-number">19</span>:<span class="hljs-number">12</span> /tmp/a/b
可以发现我们只改变了文件夹a的权限,文件夹b的权限没有变化。如果我们有一个需要,改版一个目录权限时,该目录下的文件也随着改变。我们将其权限改为766试试:
<span class="linenum hljs-number">1</span>root@atomy-virtual-machine:/tmp<br><span class="linenum hljs-number">2</span>root@atomy-virtual-machine:/tmp<br><span class="linenum hljs-number">3</span>drwxrw-rw- <span class="hljs-number">3</span> root root <span class="hljs-number">4096</span> <span class="hljs-number">5</span>月  <span class="hljs-number">10</span> <span class="hljs-number">19</span>:<span class="hljs-number">12</span> /tmp/a<br><span class="linenum hljs-number">4</span>root@atomy-virtual-machine:/tmp<br><span class="linenum hljs-number">5</span>drwxrw-rw- <span class="hljs-number">2</span> root root <span class="hljs-number">4096</span> <span class="hljs-number">5</span>月  <span class="hljs-number">10</span> <span class="hljs-number">19</span>:<span class="hljs-number">12</span> /tmp/a/b
权限 对于文件 对于目录 r——读权限 可以查看文件内容 可以列出目录中的内容 w——写权限 可以修改文件内容 可以在目录中创建、删除文件 x——执行权限 可以执行文件· 可以进入目录
特别注意w权限,举个例子:
一个目录的权限是777,该目录下一个文件的权限是700,那么创建了一个同组用户,能否删除这个文件?
答案是可以的!
因为对于文件来说,w权限只是针对修改文件内容,而删除文件的权限在目录中!
所以,题目提到目录权限是777,不管文件是什么权限,都可以被删除。
chown
- 命令名称:chown
- 英文原意:change file ownership
- 执行权限:所有用户
- 功能描述:改变文件或目录的所有者
- 语法:chown [用户] [文件或目录]
把 /var/run/httpd.pid 的所有者设置 root:
<span class="linenum hljs-number">1</span>chown root /<span class="hljs-keyword">var</span>/run/httpd.pid
将文件 file1.txt 的拥有者设为 runoob,群体的使用者 runoobgroup :
<span class="linenum hljs-number">1</span><span class="hljs-selector-tag">chown</span> <span class="hljs-selector-tag">runoob</span><span class="hljs-selector-pseudo">:runoobgroup</span> <span class="hljs-selector-tag">file1</span><span class="hljs-selector-class">.txt</span>
将当前前目录下的所有文件与子目录的拥有者皆设为 runoob,群体的使用者 runoobgroup:
<span class="linenum hljs-number">1</span><span class="hljs-selector-tag">chown</span> <span class="hljs-selector-tag">-R</span> <span class="hljs-selector-tag">runoob</span><span class="hljs-selector-pseudo">:runoobgroup</span> *
把 /home/runoob 的关联组设置为 512 (关联组ID),不改变所有者:
<span class="linenum hljs-number">1</span><span class="hljs-attribute">chown</span> :<span class="hljs-number">512</span> /home/runoob
chgrp
- 命令名称:chgrp
- 英文原意:change file group ownership
- 执行权限:所有用户
- 功能描述:改变文件或目录的所属组
- 语法:chgrp [用户组] [文件或目录]
- 选项:
- -v或–verbose 显示指令执行过程。
- -c或–changes 效果类似”-v”参数,但仅回报更改的部分。
- -f或–quiet或–silent 不显示错误信息。
- -R或–recursive 递归处理,将指定目录下的所有文件及子目录一并处理。
- -h或–no-dereference 只对符号连接的文件作修改,而不更动其他任何相关文件。
与chown命令不同,chgrp 允许普通用户改变文件所属的组,只要该用户是该组的一员。
实例1: 改变文件的群组属性
命令:
chgrp -v bin log2012.log
输出:
<span class="linenum hljs-number"> 1</span><span class="hljs-selector-attr">[root@localhost test]</span># <span class="hljs-selector-tag">ll</span><br><span class="linenum hljs-number"> 2</span><br><span class="linenum hljs-number"> 3</span><span class="hljs-selector-tag">---xrw-r--</span> 1 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">root</span> 302108 11<span class="hljs-selector-tag">-13</span> 06<span class="hljs-selector-pseudo">:03</span> <span class="hljs-selector-tag">log2012</span><span class="hljs-selector-class">.log</span><br><span class="linenum hljs-number"> 4</span><br><span class="linenum hljs-number"> 5</span><span class="hljs-selector-attr">[root@localhost test]</span># <span class="hljs-selector-tag">chgrp</span> <span class="hljs-selector-tag">-v</span> <span class="hljs-selector-tag">bin</span> <span class="hljs-selector-tag">log2012</span><span class="hljs-selector-class">.log</span><br><span class="linenum hljs-number"> 6</span><br><span class="linenum hljs-number"> 7</span>“<span class="hljs-selector-tag">log2012</span><span class="hljs-selector-class">.log</span>” 的所属组已更改为 <span class="hljs-selector-tag">bin</span><br><span class="linenum hljs-number"> 8</span><br><span class="linenum hljs-number"> 9</span><span class="hljs-selector-attr">[root@localhost test]</span># <span class="hljs-selector-tag">ll</span><br><span class="linenum hljs-number">10</span><br><span class="linenum hljs-number">11</span><span class="hljs-selector-tag">---xrw-r--</span> 1 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">bin</span> 302108 11<span class="hljs-selector-tag">-13</span> 06<span class="hljs-selector-pseudo">:03</span> <span class="hljs-selector-tag">log2012</span><span class="hljs-selector-class">.log</span>
说明:
将log2012.log文件由root群组改为bin群组
实例2: 根据指定文件改变文件的群组属性
命令:
chgrp –reference=log2012.log log2013.log
输出:
<span class="linenum hljs-number"> 1</span>[root@localhost test]<br><span class="linenum hljs-number"> 2</span><br><span class="linenum hljs-number"> 3</span>---xrw-r-- <span class="hljs-number">1</span> root bin <span class="hljs-number">302108</span> <span class="hljs-number">11</span><span class="hljs-number">-13</span> <span class="hljs-number">06</span>:<span class="hljs-number">03</span> log2012.<span class="hljs-built_in">log</span><br><span class="linenum hljs-number"> 4</span><br><span class="linenum hljs-number"> 5</span>-rw-r--r-- <span class="hljs-number">1</span> root root   <span class="hljs-number">61</span> <span class="hljs-number">11</span><span class="hljs-number">-13</span> <span class="hljs-number">06</span>:<span class="hljs-number">03</span> log2013.<span class="hljs-built_in">log</span><br><span class="linenum hljs-number"> 6</span><br><span class="linenum hljs-number"> 7</span>[root@localhost test]<br><span class="linenum hljs-number"> 8</span><br><span class="linenum hljs-number"> 9</span>[root@localhost test]<br><span class="linenum hljs-number">10</span><br><span class="linenum hljs-number">11</span>---xrw-r-- <span class="hljs-number">1</span> root bin <span class="hljs-number">302108</span> <span class="hljs-number">11</span><span class="hljs-number">-13</span> <span class="hljs-number">06</span>:<span class="hljs-number">03</span> log2012.<span class="hljs-built_in">log</span><br><span class="linenum hljs-number">12</span><br><span class="linenum hljs-number">13</span>-rw-r--r-- <span class="hljs-number">1</span> root bin   <span class="hljs-number">61</span> <span class="hljs-number">11</span><span class="hljs-number">-13</span> <span class="hljs-number">06</span>:<span class="hljs-number">03</span> log2013.<span class="hljs-built_in">log</span>
说明:
改变文件log2013.log 的群组属性,使得文件log2013.log的群组属性和参考文件log2012.log的群组属性相同
实例3:改变指定目录以及其子目录下的所有文件的群组属性
命令:
输出:
<span class="linenum hljs-number"> 1</span><span class="hljs-selector-attr">[root@localhost test]</span># <span class="hljs-selector-tag">ll</span><br><span class="linenum hljs-number"> 2</span><span class="hljs-selector-tag">drwxr-xr-x</span> 2 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">root</span>  4096 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">test6</span><br><span class="linenum hljs-number"> 3</span><span class="hljs-selector-attr">[root@localhost test]</span># <span class="hljs-selector-tag">cd</span> <span class="hljs-selector-tag">test6</span><br><span class="linenum hljs-number"> 4</span><span class="hljs-selector-attr">[root@localhost test6]</span># <span class="hljs-selector-tag">ll</span><br><span class="linenum hljs-number"> 5</span><span class="hljs-selector-tag">---xr--r--</span> 1 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">root</span> 302108 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">linklog</span><span class="hljs-selector-class">.log</span><br><span class="linenum hljs-number"> 6</span><span class="hljs-selector-tag">---xr--r--</span> 1 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">root</span> 302108 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">log2012</span><span class="hljs-selector-class">.log</span><br><span class="linenum hljs-number"> 7</span><span class="hljs-selector-tag">-rw-r--r--</span> 1 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">root</span>   61 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">log2013</span><span class="hljs-selector-class">.log</span><br><span class="linenum hljs-number"> 8</span><span class="hljs-selector-tag">-rw-r--r--</span> 1 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">root</span>   0 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">log2014</span><span class="hljs-selector-class">.log</span><br><span class="linenum hljs-number"> 9</span><span class="hljs-selector-tag">-rw-r--r--</span> 1 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">root</span>   0 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">log2015</span><span class="hljs-selector-class">.log</span><br><span class="linenum hljs-number">10</span><span class="hljs-selector-tag">-rw-r--r--</span> 1 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">root</span>   0 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">log2016</span><span class="hljs-selector-class">.log</span><br><span class="linenum hljs-number">11</span><span class="hljs-selector-tag">-rw-r--r--</span> 1 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">root</span>   0 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">log2017</span><span class="hljs-selector-class">.log</span><br><span class="linenum hljs-number">12</span><span class="hljs-selector-attr">[root@localhost test6]</span># <span class="hljs-selector-tag">cd</span> ..<br><span class="linenum hljs-number">13</span><span class="hljs-selector-attr">[root@localhost test]</span># <span class="hljs-selector-tag">chgrp</span> <span class="hljs-selector-tag">-R</span> <span class="hljs-selector-tag">bin</span> <span class="hljs-selector-tag">test6</span><br><span class="linenum hljs-number">14</span><span class="hljs-selector-attr">[root@localhost test]</span># <span class="hljs-selector-tag">cd</span> <span class="hljs-selector-tag">test6</span><br><span class="linenum hljs-number">15</span><span class="hljs-selector-attr">[root@localhost test6]</span># <span class="hljs-selector-tag">ll</span><br><span class="linenum hljs-number">16</span><span class="hljs-selector-tag">---xr--r--</span> 1 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">bin</span> 302108 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">linklog</span><span class="hljs-selector-class">.log</span><br><span class="linenum hljs-number">17</span><span class="hljs-selector-tag">---xr--r--</span> 1 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">bin</span> 302108 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">log2012</span><span class="hljs-selector-class">.log</span><br><span class="linenum hljs-number">18</span><span class="hljs-selector-tag">-rw-r--r--</span> 1 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">bin</span>   61 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">log2013</span><span class="hljs-selector-class">.log</span><br><span class="linenum hljs-number">19</span><span class="hljs-selector-tag">-rw-r--r--</span> 1 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">bin</span>   0 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">log2014</span><span class="hljs-selector-class">.log</span><br><span class="linenum hljs-number">20</span><span class="hljs-selector-tag">-rw-r--r--</span> 1 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">bin</span>   0 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">log2015</span><span class="hljs-selector-class">.log</span><br><span class="linenum hljs-number">21</span><span class="hljs-selector-tag">-rw-r--r--</span> 1 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">bin</span>   0 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">log2016</span><span class="hljs-selector-class">.log</span><br><span class="linenum hljs-number">22</span><span class="hljs-selector-tag">-rw-r--r--</span> 1 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">bin</span>   0 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">log2017</span><span class="hljs-selector-class">.log</span><br><span class="linenum hljs-number">23</span><span class="hljs-selector-attr">[root@localhost test6]</span># <span class="hljs-selector-tag">cd</span> ..<br><span class="linenum hljs-number">24</span><span class="hljs-selector-attr">[root@localhost test]</span># <span class="hljs-selector-tag">ll</span><br><span class="linenum hljs-number">25</span><span class="hljs-selector-tag">drwxr-xr-x</span> 2 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">bin</span>  4096 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">test6</span><br><span class="linenum hljs-number">26</span><span class="hljs-selector-attr">[root@localhost test]</span>#
说明:
改变指定目录以及其子目录下的所有文件的群组属性
实例4:通过群组识别码改变文件群组属性
命令:
chgrp -R 100 test6
输出:
<span class="linenum hljs-number"> 1</span><span class="hljs-selector-attr">[root@localhost test]</span># <span class="hljs-selector-tag">chgrp</span> <span class="hljs-selector-tag">-R</span> 100 <span class="hljs-selector-tag">test6</span><br><span class="linenum hljs-number"> 2</span><br><span class="linenum hljs-number"> 3</span><span class="hljs-selector-attr">[root@localhost test]</span># <span class="hljs-selector-tag">ll</span><br><span class="linenum hljs-number"> 4</span><br><span class="linenum hljs-number"> 5</span><span class="hljs-selector-tag">drwxr-xr-x</span> 2 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">users</span>  4096 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">test6</span><br><span class="linenum hljs-number"> 6</span><br><span class="linenum hljs-number"> 7</span><span class="hljs-selector-attr">[root@localhost test]</span># <span class="hljs-selector-tag">cd</span> <span class="hljs-selector-tag">test6</span><br><span class="linenum hljs-number"> 8</span><br><span class="linenum hljs-number"> 9</span><span class="hljs-selector-attr">[root@localhost test6]</span># <span class="hljs-selector-tag">ll</span><br><span class="linenum hljs-number">10</span><br><span class="linenum hljs-number">11</span><span class="hljs-selector-tag">---xr--r--</span> 1 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">users</span> 302108 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">linklog</span><span class="hljs-selector-class">.log</span><br><span class="linenum hljs-number">12</span><br><span class="linenum hljs-number">13</span><span class="hljs-selector-tag">---xr--r--</span> 1 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">users</span> 302108 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">log2012</span><span class="hljs-selector-class">.log</span><br><span class="linenum hljs-number">14</span><br><span class="linenum hljs-number">15</span><span class="hljs-selector-tag">-rw-r--r--</span> 1 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">users</span>   61 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">log2013</span><span class="hljs-selector-class">.log</span><br><span class="linenum hljs-number">16</span><br><span class="linenum hljs-number">17</span><span class="hljs-selector-tag">-rw-r--r--</span> 1 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">users</span>   0 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">log2014</span><span class="hljs-selector-class">.log</span><br><span class="linenum hljs-number">18</span><br><span class="linenum hljs-number">19</span><span class="hljs-selector-tag">-rw-r--r--</span> 1 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">users</span>   0 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">log2015</span><span class="hljs-selector-class">.log</span><br><span class="linenum hljs-number">20</span><br><span class="linenum hljs-number">21</span><span class="hljs-selector-tag">-rw-r--r--</span> 1 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">users</span>   0 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">log2016</span><span class="hljs-selector-class">.log</span><br><span class="linenum hljs-number">22</span><br><span class="linenum hljs-number">23</span><span class="hljs-selector-tag">-rw-r--r--</span> 1 <span class="hljs-selector-tag">root</span> <span class="hljs-selector-tag">users</span>   0 11<span class="hljs-selector-tag">-30</span> 08<span class="hljs-selector-pseudo">:39</span> <span class="hljs-selector-tag">log2017</span><span class="hljs-selector-class">.log</span><br><span class="linenum hljs-number">24</span><br><span class="linenum hljs-number">25</span><span class="hljs-selector-attr">[root@localhost test6]</span>#
说明:
通过群组识别码改变文件群组属性,100为users群组的识别码,具体群组和群组识别码可以去/etc/group文件中查看
umask默认权限
当我们新建一个文件或者文件夹时,系统都会默认设置权限,默认情况下的umask值是022(可以用umask命令查看),此时你建立的文件默认权限是644,建立的目录的默认权限是755,可以通过建立一个文件和文件夹通过 ls -l
验证。
当我们登录系统之后创建一个文件是会有一个默认权限的,那么这个权限是怎么来的呢?这就是umask干的事情。umask可用来设定[权限掩码]。[权限掩码]是由3个八进制的数字所组成,将现有的存取权限减掉权限掩码后,即可产生建立文件时预设的权限。
<span class="linenum hljs-number">1</span>umask [<span class="hljs-string">-S</span>][<span class="hljs-symbol">权限掩码</span>]
- -S 以文字的方式来表示权限掩码。
使用指令”umask”查看当前权限掩码,则输入下面的命令:
<span class="linenum hljs-number">1</span><span class="hljs-built_in">umask</span>
执行上面的指令后,输出信息如下:
<span class="linenum hljs-number">1</span>0022
接下来,使用指令”mkdir”创建一个目录,并使用指令”ls”获取该目录的详细信息,输入命令如下:
<span class="linenum hljs-number">1</span><span class="hljs-attribute">mkdir</span> test1 <br><span class="linenum hljs-number">2</span>ls –d –l test1/
得到结果显示,该文件夹的权限为 drwxr-xr-x
。即755。
对于文件和目录来说, 最大的权限其实都是777,但是执行权限对于文件来说是很危险的,而对目录来说执行权限是个基本权限。所以默认目录的最大权限是777,而文件的默认最大权限就是666。
对于root用户的umask=022这个来说,777权限二进制码就是(111)(111)(111),022权限二进制码为(000)(010)(010)。
- 所有权限二进制的1:代表有这个权限
- umask二进制1:代表要去掉这个权限,不管你原来有没有权限,你最终一定没有这个权限。
- umask二进制的0:代表我不关心对应位的权限,你原来有权限就有权限,没有就没有, 我不影响你。
umask为022的目录默认权限计算方法
所有者 r 所有者 w 所有者 x 所在组 r 所在组 w 所在组 x 其他 r 其他 w 其他 x 所有权限777 1 1 1 1 1 1 1 1 1 umask掩码022 0 0 0 0 1 0 0 1 0 计算后的值 1 1 1 1 0 1 1 0 1
umask为022的文件默认权限计算方法
所有者 r 所有者 w 所有者 x 所在组 r 所在组 w 所在组 x 其他 r 其他 w 其他 x 所有权限666 1 1 0 1 1 0 1 1 0 umask掩码022 0 0 0 0 1 0 0 1 0 计算后的值 1 1 0 1 0 0 1 0 0
umask为023的目录默认权限计算方法
所有者 r 所有者 w 所有者 x 所在组 r 所在组 w 所在组 x 其他 r 其他 w 其他 x 所有权限777 1 1 1 1 1 1 1 1 1 umask掩码023 0 0 0 0 1 0 0 1 1 计算后的值 1 1 1 1 0 1 1 0 0
umask为023的文件默认权限计算方法
所有者 r 所有者 w 所有者 x 所在组 r 所在组 w 所在组 x 其他 r 其他 w 其他 x 所有权限666 1 1 0 1 1 0 1 1 0 umask掩码023 0 0 0 0 1 0 0 1 1 计算后的值 1 1 0 1 0 0 1 0 0
上面就是一个umask的正常计算过程,但是这样实在是太麻烦了。我们使用如下的简单的方法快速计算。
- 对于目录,直接使用777-umask即可,就得到了最终结果。
- 对于文件,先使用666-umask。
- 如果对应位上为偶数:最终权限就是这个偶数值。
- 如果上面的对应为上有奇数,就对应位+1。
上面的这个方法计算是非常方便的, 为何得到奇数要+1呢。
文件的最大权限是666,都是偶数,你得到奇数,说明umask有奇数,读为4,写为2,都是偶数,说明你有执行权限的。
就按照上面的umask=023为例,在计算其他用户权限的时候6-3=3 ,6是读写,3是写和执行,其实应该是读写权限减去读权限的得到写权限的,相当于我们多减去了一个执行权限。所以结果加1。
Original: https://www.cnblogs.com/kylinxxx/p/14794245.html
Author: 猫坚果NutCat
Title: Linux学习笔记:Linux命令之权限管理命令
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