1、sudo介绍
sudo是linux下常用的允许普通用户使用超级用户权限的工具，允许系统管理员让普通用户执行一些或者全部的root命令，如halt，reboot，su等等。这样不仅减少了root用户的登陆 和管理时间，同样也提高了安全性。Sudo不是对shell的一个代替，它是面向每个命令的。
它的特性主要有这样几点：
§ sudo能够限制用户只在某台主机上运行某些命令。
§ sudo提供了丰富的日志，详细地记录了每个用户干了什么。它能够将日志传到中心主机或者日志服务器。
§ sudo使用时间戳文件来执行类似的“检票”系统。当用户调用sudo并且输入它的密码时，用户获得了一张存活期为5分钟的票（这个值可以在编译的时候改变）。
§ sudo的配置文件是sudoers文件，它允许系统管理员集中的管理用户的使用权限和使用的主机。它所存放的位置默认是在/etc/sudoers，属性必须为0411。
2、配置文件/etc/sudoers
它的主要配置文件是sudoers,linux下通常在/etc目录下，如果是solaris，缺省不装sudo的，编译安装后通常在安装目录的 etc目录下，不过不管sudoers文件在哪儿，sudo都提供了一个编辑该文件的命令：visudo来对该文件进行修改。强烈推荐使用该命令修改 sudoers，因为它会帮你校验文件配置是否正确，如果不正确，在保存退出时就会提示你哪段配置出错的。
言归正传，下面介绍如何配置sudoers
3、最简单的配置，让普通用户support具有root的所有权限
执行visudo之后，可以看见缺省只有一条配置：
root ALL=(ALL) ALL
那么你就在下边再加一条配置：
support ALL=(ALL) ALL
这样，普通用户support就能够执行root权限的所有命令
以support用户登录之后，执行：
sudo su -
然后输入support用户自己的密码，就可以切换成root用户了
4、让普通用户support只能在某几台服务器上，执行root能执行的某些命令
首先需要配置一些Alias，这样在下面配置权限时，会方便一些，不用写大段大段的配置。Alias主要分成4种
Host_Alias Cmmd_Alias User_Alias Runas_Alias
1) 配置Host_Alias：就是主机的列表
Host_Alias HOST_FLAG = hostname1, hostname2, hostname3
2) 配置Cmnd_Alias：就是允许执行的命令的列表
Cmnd_Alias COMMAND_FLAG = command1, command2, command3
3) 配置User_Alias：就是具有sudo权限的用户的列表
User_Alias USER_FLAG = user1, user2, user3
4) 配置Runas_Alias：就是用户以什么身份执行（例如root，或者oracle）的列表
Runas_Alias RUNAS_FLAG = operator1, operator2, operator3
5、配置权限
配置权限的格式如下：
USER_FLAG HOST_FLAG=(RUNAS_FLAG) COMMAND_FLAG
如果不需要密码验证的话，则按照这样的格式来配置
USER_FLAG HOST_FLAG=(RUNAS_FLAG) NOPASSWD: COMMAND_FLAG
用户 哪些机器=(以何种身份) 执行什么命令
配置示例：
## 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
## of related commands, which can then be delegated out to particular
## users or groups.
##
## 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
User_Alias U_DEVELOPER=%developer
## Command Aliases
## These are groups of related commands...
## Networking
# 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
# Cmnd_Alias SOFTWARE = /bin/rpm, /usr/bin/up2date, /usr/bin/yum
Cmnd_Alias C_DEVELOPER = /sbin/*,/usr/sbin/*,/bin/*,/usr/bin/*,/usr/local/php/bin/*
## Services
# Cmnd_Alias SERVICES = /sbin/service, /sbin/chkconfig
## 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
U_DEVELOPER ALL = C_DEVELOPER
# Defaults specification
#
# Refuse to run if unable to disable echo on the tty.
#
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
## 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
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