su (العربية)

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Users and groups

sudo

الأمر su هو أداة نواة لحمل هوية مستخدم آخر في النظام، وهو الجذر مبدئيًّا.

طالع PAM لمعرفة الطرق التي يمكن ضبط سلوك su بها.

التثبيت

su هو جزء من الحزمة util-linux.

الاستعمال

للولوج إلى مستخدم آخر، ضع اسم المستخدم الذي تريد أن تكون محله بعد su، مثل:

# su اسم المستخدم

سيسألك عن كلمة سر المستخدم الذي تحاول أن تكون محله.

إذا لم يوضع اسم المستخدم، فإن su ستعتبره المستخدم الجذر، وستكون كلمة السر هي كلمة سر الجذر.

لمزيد من المعلومات، طالع su(1).

البديل Sudo

sudo is a more configurable program that can provide similar functionality to su, and can be a replacement for su, depending on specific requirements and threat models. The sudo system will prompt you for your own password – or no password at all, if configured in such a way – rather than that of the target user (the user account you are attempting to use). This way you do not have to share passwords between users, and if you ever need to stop a user having root access (or access to any other account, for that matter), you do not have to change the root password, which is an inconvenience to everyone else; you only need to revoke that user's sudo access.

If sudo has been configured to allow the user to run root's shell, the user can run sudo -s or sudo -i to mimic su or su -l, respectively, and supply his own password or no password rather than root's password. Similarly, sudo -u john -i mimics su -l john if you are allowed to run john's shell.

Tips and tricks

صدفة الولوج

The default behavior of su is to remain within the current directory and to maintain the environmental variables of the original user (rather than switch to those of the new user).

Note the following important contrasting considerations:

• It sometimes can be advantageous for a system administrator to use the shell account of an ordinary user rather than its own. In particular, occasionally the most efficient way to solve a user's problem is to log into that user's account in order to reproduce or debug the problem.

• However, in many situations it is not desirable, or it can even be dangerous, for the root user to be operating from an ordinary user's shell account and with that account's environmental variables rather than from its own. While inadvertently using an ordinary user's shell account, root could install a program or make other changes to the system that would not have the same result as if they were made while using the root account. For instance, a program could be installed that could give the ordinary user power to accidentally damage the system or gain unauthorized access to certain data.

Thus, it is advisable that administrative users, as well as any other users that are authorized to use su (and it is suggested that there be very few, if any) acquire the habit of always running the su command with the -l/--login option. It has two effects:

1. switches from the current directory to the home directory of the new user (e.g., to /root in the case of the root user) by logging in as that user
2. changes the environmental variables to those of the new user as dictated by their ~/.bashrc. That is, the current directory and environment will be changed to what would be expected if the new user had actually logged on to a new session (rather than just taking over an existing session).

Thus, administrators should generally use su as follows:

$ su -l

An identical result is produced by adding the username root:

$ su -l root

Likewise, the same can be done for any other user (e.g. for a user named archie):

# su -l archie

You may wish to add an alias to ~/.bashrc for this:

alias su="su -l"

su و wheel

يسمح su الخاص بأنظمة BSD فقط للمستخدمين من المجموعة wheel بأن يأخذوا هوية الجذر مبدئيا، وهذا ليس السلوك المعروف في su الخاص بأنظمة غنو، لكن يمكن تقليد هذا السلوك باستعمال PAM. أزل علامة التعليق من السطر المناسب في /etc/pam.d/su و /etc/pam.d/su-l:

auth required pam_wheel.so use_uid