与xhost比起来，xauth是一种较为安全的授权方式。
从原则上来说，普通用户必须经过授权才能使用某个display，但一般来说，Linux系统都会进行预先的设置，对于全局环境变量的这一个DISPLAY，
# set | grep -i display
DISPLAY=:0.0
任何用户都无需经过授权，只要startx，就可以在家目录中自动产生.Xauthority文件并完成授权，顺利进入Xwindow，只是这个初始过程需要一点时间。当一个display正在被一个用户使用，那么就会在/tmp目录下产生一把锁，如果使用它的用户不退出，其它用户别想进入这个display。
如果是非全局环境变量的display，则不得不对普通用户有一个授权的方式，以便普通用户在进入Xwindow的时候可以指定进入此display。
授权方式的基本过程如下：
# xauth -f ~user_a/.Xauthority
xauth:  creating new authority file /home/user_a/.Xauthority
Using authority file /home/user_a/.Xauthority
xauth> help
    add dpyname protoname hexkey   add entry
    exit                           save changes and exit program
    extract filename dpyname...    extract entries into file
    help [topic]                   print help
    info                           print information about entries
    list [dpyname...]              list entries
    merge filename...              merge entries from files
    nextract filename dpyname...   numerically extract entries
    nlist [dpyname...]             numerically list entries
    nmerge filename...             numerically merge entries
    quit                           abort changes and exit program
    remove dpyname...              remove entries
    source filename                read commands from file
    ?                              list available commands
    generate dpyname protoname [options]  use server to generate entry
    options are:
      timeout n    authorization expiration time in seconds
      trusted      clients using this entry are trusted
      untrusted    clients using this entry are untrusted
      group n      clients using this entry belong to application group n
      data hexkey  auth protocol specific data needed to generate the entry

xauth> info
Authority file:       /home/user_a/.Xauthority
File new:             yes
File locked:          no
Number of entries:    0
Changes honored:      yes
Changes made:         no
Current input:        (stdin):1
xauth> generate :0.0
authorization id is 91
xauth> list
taurus/unix:0  MIT-MAGIC-COOKIE-1  0b093c3e6a711d680674235012340652
xauth> add :0.0 MIT-MAGIC-COOKIE-1  0b093c3e6a711d680674235012340652
xauth> info
Authority file:       /home/user_a/.Xauthority
File new:             yes
File locked:          no
Number of entries:    1
Changes honored:      yes
Changes made:         yes
Current input:        (stdin):20
xauth> exit
Writing authority file /home/user_a/.Xauthority