由於
對於 以 使用者 root 登入 的教學文章 的 論壇政策 一文
建議 :

請引領新使用者到 RootSudo 網頁
閱讀該篇網頁後 使用者將可以得到充分的知識 他們自己能夠決定 如何管理他們的系統
教育使用者 然後 允許他們自己決定 是 整個 政策的重點

特別 再把 RootSudo 一文
翻譯成中文 分享網友

這是比較多的內容 無法一次 就翻譯完畢
請允許我分次翻譯
翻譯期間
請 原文/中文 合併參考
如果翻譯用詞 您有更好的 選擇 也請不吝提供

...............RootSudo.......................................................

Note: For help with configuring sudo privileges via its configuration file /etc/sudoers, please see Sudoers.
注意:如果需要使用 設定檔案 /etc/sudoers 來設定 sudo 權限方面的 協助 請 參閱 Sudoers.

Background Information
背景資訊

In Linux (and Unix in general), there is a SuperUser named Root. The Windows equivalent of Root is Administrators group. The SuperUser can do anything and everything, and thus doing daily work as the SuperUser can be dangerous. You could type a command incorrectly and destroy the system. Ideally, you run as a user that has only the privileges needed for the task at hand. In some cases, this is necessarily Root, but most of the time it is a regular user.
在 Linux (以及 一般的 Unix) 有一個 超級使用者 名叫 Root
在 微軟的 視窗作業系統 與 Root 同義的 是 管理羣組
超級使用者 可以做任何事情以及所有的每一件事情
因此 使用 超級使用者 執行 每日例行事務 可能是 有危險性的
你可能打錯一個指令 因而 毀掉了 整個系統
比較理想是 你使用 只擁有目前手邊工作需要的權限 的 使用者 來執行目前手邊的工作
某些情況 這需要是 Root
但是 大部分時間 他只需要是 一個 一般的 使用者

By default, the Root account password is locked in Ubuntu. This means that you cannot login as Root directly or use the su command to become the Root user. However, since the Root account physically exists it is still possible to run programs with root-level privileges. This is where sudo comes in - it allows authorized users (normally "Administrative" users; for further information please refer to AddUsersHowto) to run certain programs as Root without having to know the root password.
在 Ubuntu Root 帳號 預設是 鎖住的
意思是 你不可能直接以 Root 登入
也不可能 使用 su 指令 來變成 Root 使用者
然而 因爲 Root 帳號 實際上是 存在的
因此 以 Root 層級的 專屬權利 執行 程式 仍然 是 可能的
這個情況 就是 指令 sudo 能夠發揮的地方
它允許 已被授權的使用者 (通常稱爲 管理者 請 參考 如何增加使用者 以獲得進一步的資訊)
不需知道 Root 密碼 就能夠 以 Root 身份 執行 某些程式

This means that in the terminal you should use sudo for commands that require root privileges; simply prepend sudo to all the commands you would normally run as Root. For more extensive usage examples, please see below. Similarly, when you run GUI programs that require root privileges (e.g. the network configuration applet), use graphical sudo and you will also be prompted for a password (more below). Just remember, when sudo asks for a password, it needs YOUR USER password, and not the Root account password.
這意味者 在 終端機 你應該使用 sudo 指令 來獲得 root 專屬特權
簡單地 把 sudo 加在 所有的指令 前面 你就可以 執行 平時應該以 Root 身份 執行的指令
請參考下面 有更廣泛的 使用例子
一樣的情況 你可以 用 圖形化 sudo 來執行 需要 Root 專屬特權 的 圖形界面程式 (例如 網路設定小程式)
你將會被要求輸入密碼
只是要記得 當 sudo 要求你 輸入密碼 它需要你的 使用者密碼 不是 Root 帳號密碼

Please keep in mind, a substantial number of Ubuntu users are new to Linux. There is a learning curve associated with any OS and many new users try to take shortcuts by enabling the root account, logging in as root, and changing ownership of system files.

Example: Broken system via (ab)use of root by a new user

Please note: At the time of the post, this was the users first post on the Ubuntu forums. While some may say this is a "learning experience", learning by breaking your system is frustrating and can result in data loss.

When giving advice on the Ubuntu Forums and IRC, please take the time to teach "the basics" such as ownership, permissions, and how to use sudo / gksu / kdesudo in such a way that new users do not break systems.

Advantages and Disadvantages

Benefits of using sudo

Some benefits of leaving Root logins disabled by default include the following:

The Ubuntu installer has fewer questions to ask.
Users don't have to remember an extra password (i.e. the root password), which they are likely to forget (or write down so anyone can crack into their account easily).

It avoids the "I can do anything" interactive login by default (e.g. the tendency by users to login as an "Administrator" user in Microsoft Windows systems), you will be prompted for a password before major changes can happen, which should make you think about the consequences of what you are doing.

sudo adds a log entry of the command(s) run (in /var/log/auth.log). If you mess up, you can always go back and see what commands were run. It is also nice for auditing.

Every cracker trying to brute-force their way into your box will know it has an account named Root and will try that first. What they don't know is what the usernames of your other users are. Since the Root account password is locked, this attack becomes essentially meaningless, since there is no password to crack or guess in the first place.

Allows easy transfer for admin rights, in a short term or long term period, by adding and removing users from groups, while not compromising the Root account.
sudo can be setup with a much more fine-grained security policy.
The Root account password does not need to be shared with everybody who needs to perform some type of administrative task(s) on the system (see the previous bullet).
The authentication automatically expires after a short time (which can be set to as little as desired or 0); so if you walk away from the terminal after running commands as Root using sudo, you will not be leaving a Root terminal open indefinitely.

Downsides of using sudo

Although for desktops the benefits of using sudo are great, there are possible issues which need to be noted:

Redirecting the output of commands run with sudo requires a different approach. For instance consider sudo ls > /root/somefile will not work since it is the shell that tries to write to that file. You can use ls | sudo tee -a /root/somefile to append, or ls | sudo tee /root/somefile to overwrite contents. You could also pass the whole command to a shell process run under sudo to have the file written to with root permissions, such as sudo sh -c "ls > /root/somefile".
In a lot of office environments the ONLY local user on a system is Root. All other users are imported using NSS techniques such as nss-ldap. To setup a workstation, or fix it, in the case of a network failure where nss-ldap is broken, Root is required. This tends to leave the system unusable unless cracked. An extra local user, or an enabled Root password is needed here. The local user account should have its $HOME on a local disk, _not_ on NFS (or any other networked filesystem), and a .profile/.bashrc that doesn't reference any files on NFS mounts. This is usually the case for Root, but if adding a non-Root rescue account, you will have to take these precautions manually.
Alternatively, a sysadmin type account can be implemented as a local user on all systems, and granted proper sudo privileges. As explained in the benefits section above, commands can be easily tracked and audited.

Usage

When using sudo, your password is stored by default for 15 minutes. After that time, you will need to enter your password again.

Your password will not be shown on the screen as you type it, not even as a row of stars (******). It is being entered with each keystroke!

sudo

To use sudo on the command line, preface the command with sudo, as below: Example #1

sudo chown bob:bob /home/bob/*

Example #2

sudo /etc/init.d/networking restart

To repeat the last command entered, except with sudo prepended to it, run:

sudo !!

Graphical sudo

You should never use normal sudo to start graphical applications as Root. You should use gksudo (kdesudo on Kubuntu) to run such programs. gksudo sets HOME=~root, and copies .Xauthority to a tmp directory. This prevents files in your home directory becoming owned by Root. (AFAICT, this is all that's special about the environment of the started process with gksudo vs. sudo).

Examples:

gksudo gedit /etc/fstab

or

kdesudo kate /etc/X11/xorg.conf

To run the graphical configuration utilities, simply launch the application via the Administration menu.

gksudo and kdesudo simply link to the commands gksu and kdesu

Drag & Drop sudo

This is a trick from this thread on the Ubuntu Forums.

Create a launcher with the following command:

gksudo "gnome-open %u"

When you drag and drop any file on this launcher (it's useful to put it on the desktop or on a panel), it will be opened as Root with its own associated application. This is helpful especially when you're editing config files owned by Root, since they will be opened as read only by default with gedit, etc.

Users

Allowing other users to run sudo

To add a new user to sudo, open the Users and Groups tool from System->Administration menu. Then click on the user and then on properties. Choose the User Privileges tab. In the tab, find Administer the system and check that.

In Hardy Heron and newer, you must first Unlock, then you can select a user from the list and hit Properties. Choose the User Privileges tab and check Administer the system.

Warning /!\ In the terminal (for Precise Pangolin, 12.04), this would be:

sudo adduser <username> sudo

where you replace <username> with the name of the user (without the <>).

In previous version of Ubuntu

sudo adduser <username> admin

would have been appropriate, but the admin group has been deprecated and no longer exists in Ubuntu 12.04.

Logging in as another user

Please don't use this to become Root, see further down in the page for more information about that.

sudo -i -u <username>

For example to become the user amanda for tape management purposes.

sudo -i -u amanda

The password being asked for is your own, not amanda's.

root account

Enabling the root account

IconsPage/IconWarning3.png


Enabling the Root account is rarely necessary. Almost everything you need to do as administrator of an Ubuntu system can be done via sudo or gksudo. If you really need a persistent Root login, the best alternative is to simulate a Root login shell using the following command...


IconsPage/IconWarning3.png

sudo -i

To enable the Root account (i.e. set a password) use:

sudo passwd root

Use at your own risk!

IconsPage/dont.png


Logging in to X as root may cause very serious trouble. If you believe you need a root account to perform a certain action, please consult the official support channels first, to make sure there is not a better alternative.


IconsPage/dont.png

Re-disabling your root account

IconsPage/info.png


If for some reason you have enabled your root account and wish to disable it again, use the following command in terminal...


IconsPage/info.png

sudo passwd -dl root

Other Information

Misconceptions

Isn't sudo less secure than su?

The basic security model is the same, and therefore these two systems share their primary weaknesses. Any user who uses su or sudo must be considered to be a privileged user. If that user's account is compromised by an attacker, the attacker can also gain root privileges the next time the user does so. The user account is the weak link in this chain, and so must be protected with the same care as Root.

On a more esoteric level, sudo provides some features which encourage different work habits, which can positively impact the security of the system. sudo is commonly used to execute only a single command, while su is generally used to open a shell and execute multiple commands. The sudo approach reduces the likelihood of a root shell being left open indefinitely, and encourages the user to minimize their use of root privileges.

I won't be able to enter single-user mode!
The sulogin program in Ubuntu is patched to handle the default case of a locked root password.

I can get a root shell from the console without entering a password!
You have to enter your password.

Console users have access to the boot loader, and can gain administrative privileges in various ways during the boot process. For example, by specifying an alternate init(8) program. Linux systems are not typically configured to be secure at the console, and additional steps (for example, setting a root password, a boot loader password and a BIOS password) are necessary in order to make them so. Note that console users usually have physical access to the machine and so can manipulate it in other ways as well.

Special notes on sudo and shells

None of the methods below are suggested or supported by the designers of Ubuntu.

Please do not suggest this to others unless you personally are available 24/7 to support the user if they have issues as a result of running a shell as Root.

To start a root shell (i.e. a command window where you can run Root commands), starting Root's environment and login scripts, use:

sudo -i (similar to sudo su - , gives you roots environment configuration)

To start a root shell, but keep the current shell's environment, use:

sudo -s (similar to sudo su)

For a brief overview of some of the differences between su, su -, and sudo -{i,s} see : Ubuntu Forums Post with nice table .

Summary of the differences found -

corrupted by user's
HOME=/root uses root's PATH env vars
sudo -i Y Y[2] N
sudo -s N Y[2] Y
sudo bash N Y[2] Y
sudo su N N[1] Y

[1] PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games
probably set by /etc/environment
[2] PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/X11R6/bin

For a detailed description of the differences see man su and man sudo .

Remove Password Prompt For sudo

IconsPage/IconDialog-Warning1.png


If you disable the sudo password for your account, you will seriously compromise the security of your computer. Anyone sitting at your unattended, logged in account will have complete Root access, and remote exploits become much easier for malicious crackers.


IconsPage/IconDialog-Warning1.png

This method is NOT suggested nor supported by the designers of Ubuntu.
Please do not suggest this to others unless you personally are available 24/7 to support the user if they have issues as a result of running a shell as Root.

These instructions are to remove the prompt for a password when using the sudo command. The sudo command will still need to be used for Root access though.

Edit the sudoers file

Open a Terminal window. Type in sudo visudo. Add the following line to the END of the file (if not at the end it can be nullified by later entries):

<username> ALL=NOPASSWD: ALL

Replace <username> with your user name (without the <>). This is assuming that Ubuntu has created a group with the same name as your user name, which is typical. You can alternately use the group users or any other such group you are in. Just make sure you are in that group. This can be checked by going to System->Administration->Users and Groups

Example:

michael ALL=NOPASSWD: ALL

Type in ^x to exit. This should prompt for an option to save the file, type in Y to save.

Log out, log back in. This should now allow you to run the sudo command without being prompted for a password.

Reset sudo timeout

You can make sure sudo asks for password next time by running:

sudo -k

The default sudo timeout length can be changed by following this article: RootSudoTimeout.

Other Resources

fixing sudo

graphical sudo

Ubuntu Forums policy on enabling the Root account

sudo man page

sudoers file man page