When the file or the file into the newly created folder Linux system there will always be a default permissions, then the privilege is how to set it?
umask is to set default permissions for files and directories
1. View the umask
- Direct View,
[root@centos6 ~]# umask 0022
- Modally display
[root@centos6 app]# umask -S u=rwx,g=rx,o=rx
- Output can be invoked, to redirect
[root@centos6 app]# umask -p umask 0022
0022 represents the authority rwxr-xr-x, 0 is the first bit of special privileges, not considered here first.
2. File and directory permissions
- File: The new file has execute permissions for all users is a terrible thing. So for file permissions for the default maximum is 666 rw-rw-rw
- Contents: For a directory, x means that if permission to enter the directory. If a new directory x without permission can not enter this directory. That directory would be no meaning of existence. So the largest directory permissions are 777 drwxrwxrwx
3. The calculation of default permissions
- File:
ACCESS subtract umask code is equal to the default permissions, the result is odd, odd bits +1 - The result is even
666-022 = 644, converted to a permission rw- r- - r - - -
= 135 If the mask
666-025 = 641, 642 + 1 odd, is converted to the permissions rw- -r- - - w- - Contents:
The maximum number equal rights subtract umask default permissions -
777-022 = 755 is converted into rights rwxr-xr-x
4. View Permissions
Create a file and directory permissions to view it.
[Root @ centos7data] #umask current umask of 0025 0025 [root@centos7data]#touch f1 [root@centos7data]#mkdir f2 [root@centos7data]#ll total 0 -rw-r --- w- 1 root root 0 Nov 3 11:01 f1 new file is 666-025 = 641, plus an odd number, it was: 642, -rw-r - w- drwxr-xw- 2 root root 6 Nov 3 11:01 f2 new directory is 777-025 = 752, drwx-rx-w-
5. umask setting method
- Directly, take effect only temporarily, after the user logs off recovery
[root@centos6 app]# umask 0002
- The specified user permanent
[root@centos6 app]# nano ~/.bashrc umask 0002
- Permanent for all users
[root@centos6 app]# nano /etc/.bashrc umask 0002
6. Summary
- The general root umask to 022
- Ordinary users umask to 002
- The larger the smaller the permissions umask
1. View the umask
- Direct View,
[root@centos6 ~]# umask 0022
- Modally display
[root@centos6 app]# umask -S u=rwx,g=rx,o=rx
- Output can be invoked, to redirect
[root@centos6 app]# umask -p umask 0022
0022 represents the authority rwxr-xr-x, 0 is the first bit of special privileges, not considered here first.
2. File and directory permissions
- File: The new file has execute permissions for all users is a terrible thing. So for file permissions for the default maximum is 666 rw-rw-rw
- Contents: For a directory, x means that if permission to enter the directory. If a new directory x without permission can not enter this directory. That directory would be no meaning of existence. So the largest directory permissions are 777 drwxrwxrwx
3. The calculation of default permissions
- File:
ACCESS subtract umask code is equal to the default permissions, the result is odd, odd bits +1 - The result is even
666-022 = 644, converted to a permission rw- r- - r - - -
如果mask=135
666-025=641，奇数+1为642，转换为权限rw- -r- - - w- - 目录：
最大权限减去umask码等于默认权限 -
777-022=755 转换为权限 rwxr-xr-x
4. 查看权限
创建文件与目录，查看其权限。
[root@centos7data]#umask 当前umask值为0025 0025 [root@centos7data]#touch f1 [root@centos7data]#mkdir f2 [root@centos7data]#ll total 0 -rw-r---w- 1 root root 0 Nov 3 11:01 f1 新建的文件就是666-025=641,奇数加1，则为：642， -rw-r--w- drwxr-x-w- 2 root root 6 Nov 3 11:01 f2 新建目录就是777-025=752, drwx-rx-w-
5. umask的设置方法
- 直接设置，只是临时生效，用户注销后恢复
[root@centos6 app]# umask 0002
- 对指定用户永久生效
[root@centos6 app]# nano ~/.bashrc umask 0002
- 对所有用户永久生效
[root@centos6 app]# nano /etc/.bashrc umask 0002
6. 总结
- 一般root的umask为022
- 一般普通用户的umask为002
- umask越小权限越大