Читать книгу Linux Bible - Christopher Negus - Страница 135

When you create a file as a regular user, it's given permission rw-rw-r-- by default. A directory is given the permission rwxrwxr-x. For the root user, file and directory permission are rw-r--r-- and rwxr-xr-x, respectively. These default values are determined by the value of umask. Enter umask to see what your umask value is. For example:

 $ umask 0002

If you ignore the leading zero for the moment, the umask value masks what is considered to be fully opened permissions for a file 666 or a directory 777. The umask value of 002 results in permission for a directory of 775 (rwxrwxr-x). That same umask results in a file permission of 644 (rw-rw-r--). (Execute permissions are off by default for regular files.)

To change your umask value temporarily, run the umask command. Then try creating some files and directories to see how the umask value affects how permissions are set. For example:

 $ umask 777 ; touch file01 ; mkdir dir01 ; ls -ld file01 dir01 d---------. 2 joe joe 6 Dec 19 11:03 dir01 ----------. 1 joe joe 0 Dec 19 11:02 file01 $ umask 000 ; touch file02 ; mkdir dir02 ; ls -ld file02 dir02 drwxrwxrwx. 2 joe joe 6 Dec 19 11:00 dir02/ -rw-rw-rw-. 1 joe joe 0 Dec 19 10:59 file02 $ umask 022 ; touch file03 ; mkdir dir03 ; ls -ld file03 dir03 drwxr-xr-x. 2 joe joe 6 Dec 19 11:07 dir03 -rw-r--r--. 1 joe joe 0 Dec 19 11:07 file03

If you want to change your umask value permanently, add a umask command to the .bashrc file in your home directory (near the end of that file). The next time you open a shell, your umask is set to whatever value you chose.