Linux系统文件的默认权限和特殊权限

[root@CentOS7 data]# touch file1 ; ll file1
-rw-r--r--. 1 root root 0 Oct 9 13:55 file1
[root@CentOS7 data]# mkdir dir1 ; ll dir1 -d
drwxr-xr-x. 2 root root 6 Oct 9 13:55 dir1

[root@CentOS7 data]# umask 222
[root@CentOS7 data]# touch file1 ; ll file1
-r--r--r-- 1 root root 0 Sep 30 16:41 file1

[root@CentOS7 data]# umask 123
[root@CentOS7 data]# touch file2 ; ll file2
-rw-r--r-- 1 root root 0 Sep 30 16:48 file2

[root@CentOS7 data]# mkdir dir1 ; ll dir1 -d
drw-r-xr-- 2 root root 6 Sep 30 16:49 dir1

110 110 110-->666（文件最大权限值） 
001 010 011-->123（umask值） 
110 100 100-->644（新建文件的权限） 

[root@CentOS7 data]# umask 666 ; touch file3
[root@CentOS7 data]# ll file3
---------- 1 root root 0 Sep 30 22:26 file3
[root@CentOS7 data]# umask
0666
or
[root@CentOS7 data]# touch file4 ; chmod 000 file4
[root@CentOS7 data]# ll file4
---------- 1 root root 0 Sep 30 22:33 file4

[root@CentOS7 data]# (umask 666 ; touch file5)
[root@CentOS7 data]# ll file5
---------- 1 root root 0 Sep 30 22:42 file5
[root@CentOS7 data]# umask
0022

[hechunping@CentOS7 ~]$ ll /etc/shadow
---------- 1 root root 1271 Sep 30 23:18 /etc/shadow
[hechunping@CentOS7 ~]$ passwd
Changing password for user hechunping.
Changing password for hechunping.
(current) UNIX password: 
New password: 
Retype new password: 
passwd: all authentication tokens updated successfully.
[hechunping@CentOS7 ~]$ ll /etc/shadow
---------- 1 root root 1271 Sep 30 23:23 /etc/shadow

[root@CentOS7 data]# ll `which passwd`
-rwsr-xr-x. 1 root root 27832 Jun 10 2014 /usr/bin/passwd

[root@CentOS7 data]# ll /data/ -d
drwxr-xr-x 2 root root 19 Oct 1 13:18 /data/
[root@CentOS7 data]# touch test1 ; ll test1
-rw-r--r-- 1 root root 0 Oct 1 13:19 test1

[root@CentOS7 data]# chgrp hechunping /data/ ; ll /data/ -d
drwxr-xr-x 2 root hechunping 32 Oct 1 13:19 /data/
[root@CentOS7 data]# touch test2 ; ll test2
-rw-r--r-- 1 root root 0 Oct 1 13:20 test2

[root@CentOS7 data]# chmod g+s /data/ ; ll /data/ -d
drwxr-sr-x 2 root hechunping 45 Oct 1 13:20 /data/
[root@CentOS7 data]# touch test3 ; ll test3
-rw-r--r-- 1 root hechunping 0 Oct 1 13:21 test3
[root@CentOS7 data]# mkdir dir1 ; ll dir1 -d
drwxr-sr-x 2 root hechunping 6 Oct 1 13:23 dir1
sticky

[root@CentOS7 data]# chmod 777 /data/ ; ll /data/ -d 
drwxrwxrwx 2 root root 6 Oct 1 13:56 /data/
[root@CentOS7 data]# touch file1
[root@CentOS7 data]# su - hechunping
Last login: Tue Oct 1 13:52:22 CST 2019 on pts/0
[hechunping@CentOS7 ~]$ rm -rf /data/file1 
[hechunping@CentOS7 ~]$ ls /data/
[hechunping@CentOS7 ~]$ exit
logout

[root@CentOS7 data]# chmod o+t /data/ ; ll /data/ -d
drwxrwxrwt 2 root root 6 Oct 1 13:57 /data/
[root@CentOS7 data]# touch file2 
[root@CentOS7 data]# su - hechunping
Last login: Tue Oct 1 13:56:57 CST 2019 on pts/0
[hechunping@CentOS7 ~]$ rm -rf /data/file2 
rm: cannot remove ‘/data/file2': Operation not permitted
[hechunping@CentOS7 ~]$ ll /data/
total 0
-rw-r--r-- 1 root root 0 Oct 1 13:58 file2

[root@CentOS7 data]# touch file1 ; chattr +i file1
[root@CentOS7 data]# rm -rf file1 
rm: cannot remove ‘file1': Operation not permitted
[root@CentOS7 data]# mv file1 file1.bak
mv: cannot move ‘file1' to ‘file1.bak': Operation not permitted
[root@CentOS7 data]# echo "hello"  file1 
-bash: file1: Permission denied

[root@CentOS7 data]# touch file1;chattr +a file1
[root@CentOS7 data]# echo "hello"  file1 
[root@CentOS7 data]# > file1 
-bash: file1: Operation not permitted
[root@CentOS7 data]# rm -rf file1 
rm: cannot remove ‘file1': Operation not permitted
[root@CentOS7 data]# mv file1 file1.bak
mv: cannot move ‘file1' to ‘file1.bak': Operation not permitted
[root@CentOS7 data]# echo "world"  file1

[root@CentOS7 data]# lsattr file1 
-----a---------- file1