一、sudo执行命令的流程
将当前用户切换到超级用户下,或切换到指定的用户下,
然后以超级用户或其指定切换到的用户身份执行命令,执行完成后,直接退回到当前用户。
具体工作过程如下:
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
-->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
-->若密码输入成功,则开始执行sudo后续的命令
二、不需要输入密码的情况
1.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)
2.欲切换的身份与执行者的身份相同,不需要输入密码
3./etc/sudoers文件设置为允许用户在不输入该用户的密码的情况下使用所有命令
如设置允许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)
三、/etc/sudoers文件解释
[[email protected] ~]# cat /etc/sudoers
## 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
#主机别名
## Groups of machines. You may prefer to use hostnames (perhap 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地址代替,这时可以配置主机别名
# Host_Alias FILESERVERS = fs1, fs2
# Host_Alias MAILSERVERS = smtp, smtp2
## User Aliases
#用户别名
## 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/sbin/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
#环境变量的相关配置
# 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 requiretty
Defaults env_reset
Defaults env_keep = "COLORS DISPLAY HOSTNAME HISTSIZE INPUTRC KDEDIR \
LS_COLORS MAIL PS1 PS2 QTDIR USERNAME \
LANG LC_ADDRESS LC_CTYPE LC_COLLATE LC_IDENTIFICATION \
LC_MEASUREMENT LC_MESSAGES LC_MONETARY LC_NAME LC_NUMERIC \
LC_PAPER LC_TELEPHONE LC_TIME LC_ALL LANGUAGE LINGUAS \
_XKB_CHARSET XAUTHORITY"
## 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.
# %sys ALL = NETWORKING, SOFTWARE, SERVICES, STORAGE, DELEGATING, PROCESSES, LOCATE, DRIVERS
## 允许sys中户组中的用户使用NETWORKING等所有别名中配置的命令
## Allows people in group wheel to run all commands
# %wheel ALL=(ALL) ALL
## 允许wheel用户组中的用户执行所有命令
## 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
# %users localhost=/sbin/shutdown -h now
## 允许users用户组中的用户像root用户一样使用shutdown命令
四、实际案例演示
实例1:让普通用户fieldyang具有/etc/init.d/nagios脚本重启的权限,可以在/etc/sudoers添加如下设置:
[[email protected] ~]# visudo
fieldyang ALL=NOPASSWD:/etc/init.d/nagios restart
实例2:让普通用户fieldyang具有所有超级用户的权限而又不用输入密码
[[email protected] ~]# visudo
fieldyang ALL=(ALL)NOPASSWD:ALL
[[email protected] ~]#sudo su -
[[email protected] ~]#pwd
/root
实例3:针对MySQL数据库的设置,让test组中的test用户具备/etc/init.d/mysqld的权限
######################## mysql ################
1.
[[email protected] ~]# groupadd test
[[email protected] ~]# useradd -g test -m -d /home/test -s /bin/bash test
[[email protected] ~]# passwd test
2.
[[email protected] ~]# visudo
# test ALL=(ALL) NOPASSWD: /etc/init.d/mysqld
test ALL=(ALL) /etc/init.d/mysqld
3. start/stop mysql
3.1) start mysql
login test
[[email protected] ~]# su test
[[email protected] ~]$ sudo /etc/init.d/mysqld start
3.2) stop mysql
login test
[[email protected] ~]# su test
[[email protected] ~]$ sudo /etc/init.d/mysqld stop
实例4:针对tomcat的设置,让test组中的test用户具备tomcat操作的权限
######################## tomcat ################
1.
[[email protected] ~]# groupadd test
[[email protected] ~]# useradd -g test -m -d /home/test -s /bin/bash test
[[email protected] ~]# passwd test
2.
[[email protected] ~]# visudo
# test ALL=(ALL) /usr/local/tomcat/bin/shutdown.sh,/usr/local/tomcat/bin/startup.sh
test ALL=(ALL) NOPASSWD: /usr/local/tomcat/bin/shutdown.sh,/usr/local/tomcat/bin/startup.sh
3.
[[email protected] ~]# vim /usr/local/tomcat/bin/catalina.sh
### JDK
export JAVA_HOME=/usr/local/jdk
export JRE_HOME=$JAVA_HOME/jre
4. start/stop tomcat
4.1) start tomcat
login test
[[email protected] ~]# su test
[[email protected] ~]$ sudo /usr/local/tomcat/bin/startup.sh
[[email protected] ~]$ ss -ntlup | grep Java
[[email protected] ~]$ curl -I http://localhost:8080
4.2) stop tomcat
login test
[[email protected] ~]# su test
[[email protected] ~]$ sudo /usr/local/tomcat/bin/shutdown.sh