Linux sudo

介绍

本篇文章主要介绍sudo配置和用法，为了给某个用户控制权限比如执行某个命令或者关机操作等，服务器管理员通常会给这个用户配置sudo，接下来就来详细介绍具体的配置方法。

环境：centos6.7

结构说明

可以通过编辑文件/etc/sudoers来配置，通常使用visudo命令来进行修改，visudo 后面不需要跟文件名，因为如果你修改的格式不符合它会进行提示。接下来就通过一个格式来了解它

<user> <host> = [<operator user> [<par>]] <command list>

chenmh localhost = (root)    NOPASSWD: /bin/mkdir test

<user>:指的是具体的用户或者用户别名，如果使用%user指的是用户组。

<host>:指的是具体的host(可以是机器名也可以是ip)或者是host别名，ALL代表所有的host。

<operator user>:可选，指定可以用调用哪个用户的来执行，ALL代表调用root用户来执行。这里要说明一下root用户的权限代表什么意思，比如一个目录的所有者是root，那么必须具备root用户的权限才能执行相关操作,比如上面的chenmh用户如果它配置的是其它用户比如它自己，那么它在root所有者的目录下面是没权限执行操作的。同样如果这里配置的是哪个用户那么比如mkdir创建的文件夹就的所有者就是哪个用户。默认不指定代表使用ALL

<par>:可选，指定参数，通常使用NOPASSWD（代表该用户在执行sudo的时候不需要再输入自己的密码）。

<command list>：指定的具体命令或者是命令别名或者是ALL,ALL代表所有权限。

说明： [<operator user> [<par>]]这两个选项是可以选的可以不指定，如果不指定默认是调用root用户执行，但是使用sudo必须输入用户自己的密码

配置文件

接下来详细来看看它的配置文件，它的配置文件以及很详细的告诉了我们该怎样使用，在前面一部分是示例怎样将一组权限创建组别名，注意别名需要大写，

## 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.

##可以将多个host配置成一个host别名
## Host Aliases 
## Groups of machines. You may prefer to use hostnames (perhaps using 
## wildcards for entire domains) or IP addresses instead.
Host_Alias     FILESERVERS = 192.168.137.40,192.168.137.30
# Host_Alias     MAILSERVERS = smtp, smtp2

##将多个user配置成一个user别名
## 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 = chenmh

###接下来是命令别名，就是将一组命令放在一起，这样可以简便配置
## 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

## 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

###这个是我自己配置的命令别名，将mkdir命令配置在一起分配给某个用户
##userdefin
Cmnd_Alias USERDEF = /bin/mkdir

# 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

#
# 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

## 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
###sys这个组中的用户可以执行相关的命令组的权限，多个命令组用逗号分隔
## 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
###users组的用户可以执行挂载和卸载/mnt/cdrom目录的权限
## Allows members of the users group to shutdown this system
# %users  localhost=/sbin/shutdown -h now
###users组的用户可以执行关机命令
## Read drop-in files from /etc/sudoers.d (the # here does not mean a comment)
#includedir /etc/sudoers.d

案例

1.用户别名组中的用户可以在FILESERVERS这组host里面调用root用户执行OTHERS命令组的权限，多个命令组用逗号分隔

ADMINS  FILESERVERS=(ALL)    NOPASSWD:OTHERS

2.用户chenmh这个用户可以在本机以调用root用户来执行所有的命令

chenmh localhost=(root) NOPASSWORD:ALL

3.用户chenmh可以调用root用户创建目录test，也只能创建test目录

chenmh ALL=(ALL)    NOPASSWD: /bin/mkdir test

4.dev组的用户可以执行关机shutdown命令

%dev ALL=(ALL)    NOPASSWD:/sbin/shutdown

 

备注：一般的用户只需要授予以下权限即可：

test ALL=(ALL)       NOPASSWD:NETWORKING, SOFTWARE, SERVICES, PROCESSES, USERDEF

快捷操作 

 1.查看当前用户具备的sudo权限

sudo -l

User chenmh may run the following commands on this host:
    (root) NOPASSWD: /bin/mkdir, /bin/rm

总结

配置sudo记得使用visudo命令，如果配置错误了保存的时候它会有提示。 一般用户只需要拥有个别文件夹的所有权限，root用户只需要授予用户指定文件夹的所有权限即可。对用户授予chown权限要特别注意，一旦用户拥有chown权限用户就可以将文件或者文件夹的所有者置为自己，一旦用户拥有了某个文件或者文件夹的所有权限，那么也就可以删除该文件或者文件夹。

备注：

    作者：pursuer.chen

    博客：http://www.cnblogs.com/chenmh

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