My user name is in sudoer file
check ALL=(ALL) ALL
But, when I want to restart server by check user the error is shown:
reboot: must be superuser.

what exact command are you typing to reboot the system?

type the following and copy/past here using code flags:

after that then type the following:

put in the users p/w and the system should shutdown and reboot.

/sbin/reboot
I get "Permission denied" to run a file in etc, too.for example: /etc/sudoers

/etc/sudoers is not an executable, you cannot run it.
/sbin/reboot cannot be run as normal user, you need to execute it as sudo /sbin/reboot.
I hope this helps

Kind of some issues here.

One is whether or not you have in fact been granted to be a super user or sudo'ed to some other level.

Since we are getting permission denied, we assume it is for the single command that you issued. Is it really a command or is it a script or other that calls to a different command.

A sudo to some command should run all that root can. See what sudo whoami says.

It may be that root has been changed.

ok, thats fine and dandy, but you didnt follow directions. please copy/paste the info requested above and follow the directions for rebooting the system via sudo.

whoami

check
pwd
/home/check

sudo shutdown -r now


>>> /etc/sudoers: syntax error near line 17 <<<
sudo: parse error in /etc/sudoers near line 17
sudo: no valid sudoers sources found, quitting

,is shown!
The content of my soduers file is in below:
# /etc/sudoers
#
# This file MUST be edited with the 'visudo' command as root.
#
# See the man page for details on how to write a sudoers file.
#

Defaults env_reset

# Host alias specification

# User alias specification

# Cmnd alias specification

# User privilege specification
root ALL=(ALL) ALL
check ALL=ALL(ALL) ALL

# Allow members of group sudo to execute any command
# (Note that later entries override this, so you might need to move
# it further down)
%sudo ALL=(ALL) ALL
#
#includedir /etc/sudoers.d

you should edit that file using the command visudo. It contains a syntax error at this moment, therefore sudo will not work

thank you. please use code and quote flags... like so, just remove the extra spacing... [ code ] stuff goes here [ / code ]

will make life much simpler to read.

As pointed out above as root you need to run the command visudo and fix the error on line 17. This is the wonderful thing about Linux. it is telling you exactly were the problem is.

http://www.sudo.ws/sudo/sample.sudoers

that is a good link for how to setup a visudo for sudoers to function properly.

The lines you might be interested in:

note the use of the code flags for this. much simpler to read.

You might want to add a line in there that looks like this:
or be more specific as you are just trying to shutdown the system as check

this should allow check to execute the shutdown command via sudo.