sudo的工作过程如下：
1，当用户执行sudo时，系统会主动寻找/etc/sudoers文件，判断该用户是否有执行sudo的权限
2，确认用户具有可执行sudo的权限后，让用户输入用户自己的密码确认
3，若密码输入成功，则开始执行sudo后续的命令
4，root执行sudo时不需要输入密码(eudoers文件中有配置root ALL=(ALL) ALL这样一条规则)
5，若欲切换的身份与执行者的身份相同，也不需要输入密码
visudo使用vi打开/etc/sudoers文件，但是在保存退出时，visudo会检查内部语法，避免用户输入错误信息
visudo需要root权限
使用visudo命令打开sudo配置文件
## Sudoers allows particular users to run various commands as ## the root user, without needing the root password. ## 该文件允许特定用户像root用户一样使用各种各样的命令，而不需要root用户的密码 ## ## 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关命令的示例以供选择，这些示例都可以被特定用户或 ## 用户组所使用 ## ## This file must be edited with the 'visudo' command. ## 该文件必须使用"visudo"命令编辑 ## Host Aliases ## Groups of machines. You may prefer to use hostnames (perhaps using ## wildcards for entire domains) or IP addresses instead. ## 对于一组服务器，你可能会更喜欢使用主机名（可能是全域名的通配符） ## 、或IP地址，这时可以配置主机别名 # 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 ## 这并不很常用，因为你可以通过使用组来代替一组用户的别名 # User_Alias ADMINS = jsmith, mikem ## Command Aliases ## These are groups of related commands... ## 指定一系列相互关联的命令（当然可以是一个）的别名，通过赋予该别名sudo权限， ## 可以通过sudo调用所有别名包含的命令，下面是一些示例 ## Networking 网络操作相关命令别名 # 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 软件安装管理相关命令别名 # Cmnd_Alias SOFTWARE = /bin/rpm, /usr/bin/up2date, /usr/bin/yum ## Services 服务相关命令别名 # Cmnd_Alias SERVICES = /sbin/service, /sbin/chkconfig ## Updating the locate database 本地数据库升级命令别名 # Cmnd_Alias LOCATE = /usr/bin/updatedb ## Storage 磁盘操作相关命令别名 # Cmnd_Alias STORAGE = /sbin/fdisk, /sbin/sfdisk, /sbin/parted, /sbin/partprobe , /bin/mount, /bin/umount ## Delegating permissions 代理权限相关命令别名 # Cmnd_Alias DELEGATING = /usr/sbin/visudo, /bin/chown, /bin/chmod, /bin/chgrp ## Processes 进程相关命令别名 # Cmnd_Alias PROCESSES = /bin/nice, /bin/kill, /usr/bin/kill, /usr/bin/killall ## Drivers 驱动命令别名 # 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>". # 一些环境变量的相关配置，具体情况可见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). ## 下面是规则配置：什么用户在哪台服务器上可以执行哪些命令（sudoers文件可以在多个系统上共享） ## Syntax(语法): ## ## user MACHINE=COMMANDS 用户 登录的主机=（可以变换的身份） 可以执行的命令 ## ## The COMMANDS section may have other options added to it. ## 命令部分可以附带一些其它的选项 ## ## Allow root to run any commands anywhere ## 允许root用户执行任意路径下的任意命令 root ALL=(ALL) ALL ## Allows members of the 'sys' group to run networking, software, ## service management apps and more. ## 允许sys中户组中的用户使用NETWORKING等所有别名中配置的命令 # %sys ALL = NETWORKING, SOFTWARE, SERVICES, STORAGE, DELEGATING, PROCESSES, LOCATE , DRIVERS ## Allows people in group wheel to run all commands ## 允许wheel用户组中的用户执行所有命令 %wheel ALL=(ALL) ALL ## Same thing without a password ## 允许wheel用户组中的用户在不输入该用户的密码的情况下使用所有命令 # %wheel ALL=(ALL) NOPASSWD: ALL ## Allows members of the users group to mount and unmount the ## cdrom as root ## 允许users用户组中的用户像root用户一样使用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 ## 允许users用户组中的用户关闭localhost这台服务器 # %users localhost=/sbin/shutdown -h now ## Read drop-in files from /etc/sudoers.d (the # here does not mean a comment) ## 读取放置在/etc/sudoers.d/文件夹中的文件（此处的#不意味着这是一个声明） #includedir /etc/sudoers.d
#参考配置
[ceph@admin-node ~]$ 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 #添加一个普通用户，切换时不需要密码
## 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
[ceph@node4 ~]$ sudo visudo -c /etc/sudoers: parsed OK /etc/sudoers.d/ceph: parsed OK