Linux sudo 命令使用简介
基本语法：
$ sudo [-u username] [command]
-u：将身份变成username的身份
#编辑/etc/sudoers (注意，这里使用 visudo 而不是 vi 来设置。）
# 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
## of related commands, which can then be delegated out to particular
## users or groups.
##
## 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
## 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.
##
## 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
# Cmnd_Alias SERVICES = /sbin/service, /sbin/chkconfig
## Updating the locate database
# Cmnd_Alias LOCATE = /usr/bin/updatedb
## Storage
## 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 ", because it will show the password in clear.
# You have to run "ssh -t hostname sudo ".
#
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
# 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
laiyu ALL=(ALL) ALL #根据上述提示，模仿root用户添加自定义用户laiyu，使其可执行sudo命令
test 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 ##这行默认是注释掉的。如果取消注释，则群组为 wheel 的人就可以进行root 的身份工作！这个 wheel 是系统预设的 group！因此，如果想要让这部主机里头的一般身份使用者具有sudo 的使用权限，那么就必需将该 user 放入支持 wheel 这个群组里头！
## Same thing without a password
# %wheel ALL=(ALL) NOPASSWD: ALL #默认是注释掉的，运行所有wheel组群的用户不实用密码
## 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
实验检验真理：
[root@localhost ~]# su laiyu
[laiyu@localhost root]$ pwd
/root
[laiyu@localhost root]$ mkdir test
mkdir: cannot create directory `test': Permission denied
[laiyu@localhost root]$ sudo mkdir test ##在以laiyu身份在/root目录下创建test文件
We trust you have received the usual lecture from the local System
Administrator. It usually boils down to these three things:
#1) Respect the privacy of others.
#2) Think before you type.
#3) With great power comes great responsibility.
[sudo] password for laiyu:
Sorry, try again.
[sudo] password for laiyu: ##注意这里输入的是用户laiyu自己的密码，而不是root的密码
[laiyu@localhost root]$ ls
ls: cannot open directory .: Permission denied
[laiyu@localhost root]$ sudo ls
anaconda-ks.cfg file install.log install.log.syslog myfile test
[laiyu@localhost root]$
[laiyu@localhost root]$ su root
Password:
[root@localhost ~]# sudo -u laiyu rm test #说明不能以root身份 sudo –u 普通身份
rm: cannot remove `test': Permission denied
[root@localhost ~]# sudo
usage: sudo -h | -K | -k | -L | -V
usage: sudo -v [-AknS] [-g groupname|#gid] [-p prompt] [-u user name|#uid]
usage: sudo -l[l] [-AknS] [-g groupname|#gid] [-p prompt] [-U user name] [-u user name|#uid] [-g groupname|#gid] [command]
usage: sudo [-AbEHknPS] [-r role] [-t type] [-C fd] [-g groupname|#gid] [-p prompt] [-u user name|#uid] [-g groupname|#gid] [VAR=value] [-i|-s] []
usage: sudo -e [-AknS] [-r role] [-t type] [-C fd] [-g groupname|#gid] [-p prompt] [-u user name|#uid] file ...
[root@localhost ~]# su laiyu
[laiyu@localhost root]$ sudo -u root rmdir test #这样成功了
[laiyu@localhost ~]$ su - test
Password:
[test@localhost ~]$ pwd
/home/test
[test@localhost ~]$ sudo -u laiyu mkdir -p /home/laiyu/tes #成功从普通用户test切换到普通用户laiyu执行命令
[test@localhost ~]$ su - laiyu
Password:
[laiyu@localhost ~]$ ls /home/laiyu
tes
[laiyu@localhost ~]$