问题:

I found some Linux files, and when I type ls -lah, it outputs this permissions format:

... 
drwxr-xr-x.  2 root    root  
...
-rw-rw-r--.  1 root    root 
...

I would like to know what is a meaning of dot (-rw-rw-r--.) at end of permissions format?

回答1:

From info coreutils 'ls invocation' under Linux

GNU `ls' uses a `.' character to indicate a file with an SELinux
     security context, but no other alternate access method.

A file with any other combination of alternate access methods is
     marked with a `+' character.

回答2:

From GNU.org under what information is listed:

GNU ls uses a ‘.’ character to indicate a file with a SELinux security context, but no other alternate access method.

This basically implies that the file has an Access Control List (ACL) with SELinux. You can set or delete ACL association for a file by using the setfacl command