permission

user

su:

1. what

   1. change user
   2. excute a command as another

2. how

3. -, -l: simulate a full login

4. -c: excute command

user - group

1. file belong to a group which the owner doesnt belong to
   yes: share the data to other groups /public.html owner: root, group: apache,www

inspect permission

permission list

excute permission for directory

1. read:

   1. read list: ls

2. write: delte/update/add the items(must enter the item first)

3. excute:

   1. cd
   2. read the meta of item: ls -l

      1 2 3 4 5

      01/01.txt ls -l 01 ls: cannot access '01/01.txt': Permission denied total 0 -????????? ? ? ? ? ? 01.txt

   /var/root: rwx — —;

4. permiss list

   1. noraml

      1. read:+r
      2. write:+w
      3. excute:x

   2. supplement,special permission bits

      1. sticky:+t, only the owner can rename/delete the file
      2. setuid,setgid: +s, grant permission temporarily

         1	-rwsr-xr-x root root /usr/bin/passwd

         other user run passwd as root

change permission

umask

1. what? change the file permissions

2. when

   1. change new filles: processs(toucch,mkdir).
   2. chmod with symbol

3. how:

   1. file: 666-unmask(022): user:rw, group/other: r
   2. directory: 777-unmask(022) user:rwx ,group/other:rx;

chmod

1. what change the permission of the files

2. types

   1. number: chmod 777 a
   2. symbol:(will delete the maskvalue)
      1. chmod ugo=rwx,a=rwx;
      2. chmod u=rwx,g=rwx,o+r