理解 sudo 和 sudoers

在 Linux 上, 只有 root 用户可以执行任何命令, 其他用户必须使用 sudo 才可执行特殊的命令.

sudo 是通过 sudoers 进行配置的.

默认配置

/etc/sudoers:

#
# This file MUST be edited with the 'visudo' command as root.
#
# Please consider adding local content in /etc/sudoers.d/ instead of
# directly modifying this file.
#
# See the man page for details on how to write a sudoers file.
#
Defaults        env_reset
Defaults        mail_badpass
Defaults        secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin"

# Host alias specification

# User alias specification

# Cmnd alias specification

# User privilege specification
root    ALL=(ALL:ALL) ALL

# Members of the admin group may gain root privileges
%admin ALL=(ALL) ALL

# Allow members of group sudo to execute any command
%sudo   ALL=(ALL:ALL) ALL

# See sudoers(5) for more information on "#include" directives:

#includedir /etc/sudoers.d

添加配置

不建议直接修改默认配置文件, 我们可以使用 #include 和 #includedir 添加自定义的配置文件.

/etc/sudoers.d/README:

#
# As of Debian version 1.7.2p1-1, the default /etc/sudoers file created on
# installation of the package now includes the directive:
# 
# #includedir /etc/sudoers.d
# 
# This will cause sudo to read and parse any files in the /etc/sudoers.d 
# directory that do not end in '~' or contain a '.' character.
# 
# Note that there must be at least one file in the sudoers.d directory (this
# one will do), and all files in this directory should be mode 0440.
# 
# Note also, that because sudoers contents can vary widely, no attempt is 
# made to add this directive to existing sudoers files on upgrade. Feel free
# to add the above directive to the end of your /etc/sudoers file to enable 
# this functionality for existing installations if you wish!
#
# Finally, please note that using the visudo command is the recommended way
# to update sudoers content, since it protects against many failure modes.
# See the man page for visudo for more information.
#

理解配置

root    ALL=(ALL:ALL) ALL

上面的配置表示: root 用户可以在 任意机器 上以 任意用户 和 任意用户组 的 任意组合 执行 任意命令.

• root: 用户 (%admin 表示 用户组)
• ALL=: 所有 host (sudoers 配置可能被用到多台机器上)
• ALL:: 任意 用户
• :ALL: 任意 用户组
• ALL: 任意 命令

常见配置

允许用户使用 sudo 执行任意命令, 但需要输入用户密码

user ALL=(ALL:ALL) ALL

允许用户不需要密码使用 sudo 执行任意命令

user ALL=(ALL:ALL) NOPASSWD: ALL

参考文档

• What is the difference between root ALL=(ALL:ALL) ALL and root ALL=(ALL) ALL?
• Sudoers file, enable NOPASSWD for user, all commands
• Sudoers Manual

原文链接: k8scat.com/posts/linux…