sudo的工作過程如下：

1，當用戶執行sudo時，系統會主動尋找/etc/sudoers文件，判斷該用戶是否有執行sudo的權限

2，確認用戶具有可執行sudo的權限後，讓用戶輸入用戶自己的密碼確認

3，若密碼輸入成功，則開始執行sudo後續的命令

4，root執行sudo時不需要輸入密碼(eudoers文件中有配置root ALL=(ALL) ALL這樣一條規則)

5，若欲切換的身份與執行者的身份相同，也不需要輸入密碼

visudo使用vi打開/etc/sudoers文件，但是在保存退出時，visudo會檢查內部語法，避免用戶輸入錯誤信息

visudo需要root權限

[[email protected] ~]$ visudo  
visudo：/etc/sudoers：權限不夠  
visudo：/etc/sudoers：權限不夠  

使用visudo命令打開sudo配置文件

## Sudoers allows particular users to run various commands as  
## the root user, without needing the root password.  
## 該文件允許特定用戶像root用戶一樣使用各種各樣的命令，而不需要root用戶的密碼  
##  
## Examples are provided at the bottom of the file for collections  
## of related commands, which can then be delegated out to particular  
## users or groups.  
## 在文件的底部提供了很多相關命令的示例以供選擇，這些示例都可以被特定用戶或  
## 用戶組所使用   
##  
## This file must be edited with the ‘visudo‘ command.  
## 該文件必須使用"visudo"命令編輯  
  
## Host Aliases  
## Groups of machines. You may prefer to use hostnames (perhaps using   
## wildcards for entire domains) or IP addresses instead.  
## 對於一組服務器，你可能會更喜歡使用主機名（可能是全域名的通配符）  
## 、或IP地址，這時可以配置主機別名  
# Host_Alias     FILESERVERS = fs1, fs2  
# Host_Alias     MAILSERVERS = smtp, smtp2  
  
## User Aliases  
## These aren‘t often necessary, as you can use regular groups  
## (ie, from files, LDAP, NIS, etc) in this file - just use %groupname   
## rather than USERALIAS  
## 這並不很常用，因為你可以通過使用組來代替一組用戶的別名  
# User_Alias ADMINS = jsmith, mikem  
  
## Command Aliases  
## These are groups of related commands...  
## 指定一系列相互關聯的命令（當然可以是一個）的別名，通過賦予該別名sudo權限，  
## 可以通過sudo調用所有別名包含的命令，下面是一些示例  
  
## Networking 網絡操作相關命令別名  
# Cmnd_Alias NETWORKING = /sbin/route, /sbin/ifconfig, /bin/ping, /sbin/dhclient  
, /usr/bin/net, /sbin/iptables, /usr/bin/rfcomm, /usr/bin/wvdial, /sbin/iwconfig  
, /sbin/mii-tool  
  
## Installation and management of software 軟件安裝管理相關命令別名  
# Cmnd_Alias SOFTWARE = /bin/rpm, /usr/bin/up2date, /usr/bin/yum  
  
## Services 服務相關命令別名  
# Cmnd_Alias SERVICES = /sbin/service, /sbin/chkconfig  
  
## Updating the locate database 本地數據庫升級命令別名  
# Cmnd_Alias LOCATE = /usr/bin/updatedb  
  
## Storage 磁盤操作相關命令別名  
# Cmnd_Alias STORAGE = /sbin/fdisk, /sbin/sfdisk, /sbin/parted, /sbin/partprobe  
, /bin/mount, /bin/umount  
  
## Delegating permissions 代理權限相關命令別名  
# Cmnd_Alias DELEGATING = /usr/sbin/visudo, /bin/chown, /bin/chmod, /bin/chgrp   
  
## Processes 進程相關命令別名  
# Cmnd_Alias PROCESSES = /bin/nice, /bin/kill, /usr/bin/kill, /usr/bin/killall  
  
## Drivers 驅動命令別名  
# Cmnd_Alias DRIVERS = /sbin/modprobe  
  
# Defaults specification  
  
#  
# Disable "ssh hostname sudo <cmd>", because it will show the password in clear.   
#         You have to run "ssh -t hostname sudo <cmd>".  
# 一些環境變量的相關配置，具體情況可見man soduers  
Defaults    requiretty  
  
Defaults    env_reset  
Defaults    env_keep =  "COLORS DISPLAY HOSTNAME HISTSIZE INPUTRC KDEDIR LS_COLORS"  
Defaults    env_keep += "MAIL PS1 PS2 QTDIR USERNAME LANG LC_ADDRESS LC_CTYPE"  
Defaults    env_keep += "LC_COLLATE LC_IDENTIFICATION LC_MEASUREMENT LC_MESSAGES"  
Defaults    env_keep += "LC_MONETARY LC_NAME LC_NUMERIC LC_PAPER LC_TELEPHONE"  
Defaults    env_keep += "LC_TIME LC_ALL LANGUAGE LINGUAS _XKB_CHARSET XAUTHORITY"  
  
Defaults    secure_path = /sbin:/bin:/usr/sbin:/usr/bin  
  
## Next comes the main part: which users can run what software on   
## which machines (the sudoers file can be shared between multiple  
## systems).  
## 下面是規則配置：什麽用戶在哪臺服務器上可以執行哪些命令（sudoers文件可以在多個系統上共享）  
## Syntax(語法):  
##  
##  user    MACHINE=COMMANDS 用戶 登錄的主機=（可以變換的身份） 可以執行的命令  
##  
## The COMMANDS section may have other options added to it.  
## 命令部分可以附帶一些其它的選項  
##  
## Allow root to run any commands anywhere   
## 允許root用戶執行任意路徑下的任意命令  
root    ALL=(ALL)   ALL  
  
## Allows members of the ‘sys‘ group to run networking, software,   
## service management apps and more.  
## 允許sys中戶組中的用戶使用NETWORKING等所有別名中配置的命令  
# %sys ALL = NETWORKING, SOFTWARE, SERVICES, STORAGE, DELEGATING, PROCESSES, LOCATE  
, DRIVERS  
  
## Allows people in group wheel to run all commands  
## 允許wheel用戶組中的用戶執行所有命令  
%wheel  ALL=(ALL)   ALL  
  
## Same thing without a password  
## 允許wheel用戶組中的用戶在不輸入該用戶的密碼的情況下使用所有命令  
# %wheel    ALL=(ALL)   NOPASSWD: ALL  
  
## Allows members of the users group to mount and unmount the   
## cdrom as root  
## 允許users用戶組中的用戶像root用戶一樣使用mount、unmount、chrom命令  
# %users  ALL=/sbin/mount /mnt/cdrom, /sbin/umount /mnt/cdrom  
  
## Allows members of the users group to shutdown this system  
## 允許users用戶組中的用戶關閉localhost這臺服務器  
# %users  localhost=/sbin/shutdown -h now  
  
## Read drop-in files from /etc/sudoers.d (the # here does not mean a comment)  
## 讀取放置在/etc/sudoers.d/文件夾中的文件（此處的#不意味著這是一個聲明）  
#includedir /etc/sudoers.d 

#參考配置

[[email protected] ~]$ sudo visudo
## Sudoers allows particular users to run various commands as
## the root user, without needing the root password.
##
## Examples are provided at the bottom of the file for collections
##
## This file must be edited with the ‘visudo‘ command.

## Host Aliases
## Groups of machines. You may prefer to use hostnames (perhaps using
## wildcards for entire domains) or IP addresses instead.
# Host_Alias     FILESERVERS = fs1, fs2
# Host_Alias     MAILSERVERS = smtp, smtp2

## User Aliases
## These aren‘t often necessary, as you can use regular groups
## (ie, from files, LDAP, NIS, etc) in this file - just use %groupname
## rather than USERALIAS
# User_Alias ADMINS = jsmith, mikem


## Command Aliases
## These are groups of related commands...

## Networking

## Installation and management of software
# Cmnd_Alias SOFTWARE = /bin/rpm, /usr/bin/up2date, /usr/bin/yum

## Services

## Updating the locate database
# Cmnd_Alias LOCATE = /usr/bin/updatedb

## Storage
# Cmnd_Alias STORAGE = /sbin/fdisk, /sbin/sfdisk, /sbin/parted, /sbin/partprobe, /bin/mount, /bin/umount

## Delegating permissions
# Cmnd_Alias DELEGATING = /usr/sbin/visudo, /bin/chown, /bin/chmod, /bin/chgrp

## Processes
# Cmnd_Alias PROCESSES = /bin/nice, /bin/kill, /usr/bin/kill, /usr/bin/killall

## Drivers
# Cmnd_Alias DRIVERS = /sbin/modprobe

# Defaults specification

#
# Disable "ssh hostname sudo <cmd>", because it will show the password in clear.
#         You have to run "ssh -t hostname sudo <cmd>".
#
Defaults:ceph  !requiretty

#
# Refuse to run if unable to disable echo on the tty. This setting should also be
# changed in order to be able to use sudo without a tty. See requiretty above.
#
Defaults   !visiblepw

#
# Preserving HOME has security implications since many programs
# use it when searching for configuration files. Note that HOME
# is already set when the the env_reset option is enabled, so
# this option is only effective for configurations where either
# env_reset is disabled or HOME is present in the env_keep list.
#
Defaults    always_set_home

Defaults    env_reset
Defaults    env_keep =  "COLORS DISPLAY HOSTNAME HISTSIZE INPUTRC KDEDIR LS_COLORS"
Defaults    env_keep += "MAIL PS1 PS2 QTDIR USERNAME LANG LC_ADDRESS LC_CTYPE"
Defaults    env_keep += "LC_COLLATE LC_IDENTIFICATION LC_MEASUREMENT LC_MESSAGES"
Defaults    env_keep += "LC_MONETARY LC_NAME LC_NUMERIC LC_PAPER LC_TELEPHONE"
Defaults    env_keep += "LC_TIME LC_ALL LANGUAGE LINGUAS _XKB_CHARSET XAUTHORITY"

#
# Adding HOME to env_keep may enable a user to run unrestricted
# commands via sudo.
#
# Defaults   env_keep += "HOME"

Defaults    secure_path = /sbin:/bin:/usr/sbin:/usr/bin

## Next comes the main part: which users can run what software on
## which machines (the sudoers file can be shared between multiple
## systems).
## Syntax:
##
##      user    MACHINE=COMMANDS
##
## The COMMANDS section may have other options added to it.
##
## Allow root to run any commands anywhere
root    ALL=(ALL)       ALL
ceph    ALL=(root)      NOPASSWD: ALL   #添加一個普通用戶，切換時不需要密碼
 


## Allows members of the ‘sys‘ group to run networking, software,
## service management apps and more.
# %sys ALL = NETWORKING, SOFTWARE, SERVICES, STORAGE, DELEGATING, PROCESSES, LOCATE, DRIVERS

## Allows people in group wheel to run all commands
%wheel  ALL=(ALL)       ALL

## Same thing without a password
# %wheel        ALL=(ALL)       NOPASSWD: ALL

## Allows members of the users group to mount and unmount the
## cdrom as root
# %users  ALL=/sbin/mount /mnt/cdrom, /sbin/umount /mnt/cdrom

## Allows members of the users group to shutdown this system
# %users  localhost=/sbin/shutdown -h now

## Read drop-in files from /etc/sudoers.d (the # here does not mean a comment)
#includedir /etc/sudoers.d

#使配置生效

[[email protected] ~]$ sudo visudo -c
/etc/sudoers: parsed OK
/etc/sudoers.d/ceph: parsed OK

Linux用戶配置sudo權限(visudo)