Linux Account and Identity management

▲ Identity Information Description

Root:x:0:0:root:/root:/bin/bash???????? Store in/etc/passwd

???? The first root???? User name

???? A second x???? Password (use MD5 encryption, total 34 bits, view in/etc/shadow, first three bits is $1$)

???? A third 0???? Uid

???? Fourth of 0???? GID (represents the root user's initialization user group, which is its effective user group)

???? Fifth root???? User Description

???? Sixth a/root???? User home Directory

???? Seventh a/bin/bash???? The shell used

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When the UID is 0 o'clock, this account is the system administrator. 1~99 reserved to the System preset account, 100~499 is reserved for some services to use. 500~2^32-1 is used by the general user.

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Use Uname–r to view the core of a Linux system

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Use groups to view the user group to which root belongs, the first domain is a valid user group

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Use NEWGRP to change the active user group of the currently logged on user

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Use Exit to exit the current user group

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▲ User additions and deletions

Useradd [-U UID] [-G initial_group] [-G other_group] [-mm] [-C description Bar] [-D home] [-s Shell] Username

???? Parameter-G???????? Groups that can be supported. This parameter will modify the relevant data in/etc/group and/etc/gshadow.

???? Parameter-M???? Force does not establish user home directory

???? Parameter-m???????? Force User Home Directory creation

???? Parameter-R???????? Establish a System account, the UID of this account will be limited (between 100~499)

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Userdel [-RF] Username

???? Parameter-R???????? User's home directory is deleted together

???? Parameter-F???????? Even if the user logged in, also forced to delete, while home directory and mailbox, such as delete together

Secure method: First Find/-user username investigate the entire system belongs to the username file, and then Userdel delete

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passwd [-LUNXWS] Username

???? Parameter-l???????? Lock the password of this account, modify the password bar in the/etc/passwd

???? Parameter-u???????? Unlock the Lock

???? Parameter-n???????? Number of days followed, indicating that no password changes are allowed within a few days

???? Parameter-x???????? Number of days after which the password needs to be re-modified

???? Parameter-W???????? The number of days to follow, indicating a few days in advance to remind users to change password

???? Parameter-s???????? Show information about the username

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Usermod [-cdeqglsulu] Username

???? Parameter-u???????? followed by the UID number (/etc/passwd in the third column)

???? Parameter-G???????? Followed by group name (fourth column in/etc/passwd)

???? Parameter-G???????? Follow the group name (/etc/group) and modify the user-supported groups

???? Parameter-c???????? Access Account description (/etc/passwd fifth column)

???? Parameter-D???????? Access Account Home Directory (/etc/passwd sixth column)

???? Parameter-s???????? Access the Shell's actual file and modify the shell used by the user

???? Parameter-e???????? After date yyyy-mm-dd (/etc/shadow), account expiration date

???? Parameter-l???????? Receive account name (/etc/passwd first column)

???? Parameter-l???????? Temporarily freezes the user's password and cannot log in (/etc/shadow's password bar)

???? Parameter-u???????? /etc/shadow the password bar! Take it off, unlock it.

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Linux Account and Identity management