How to change user ID and password on Linux system

How to change username and password in linux

Shell command passwd is used to specify and modify user passwords. Super users can specify passwords for themselves and other users, and ordinary users can only modify their own passwords. The command format is:

passwd options username

Available options:

-l Lock the password, that is, disable the account.

-u Password unlock.

-d makes the account without password.

-f Forces the user to change their password the next time they log in.

If the default user name is used, modify the current user's password.

For example, assuming that the current user is sam, the following command changes the user's own password:

$ passwd

Old password:******

New password:*******

Re-enter new password:*******

If you are a super user, you can specify the password of any user in the following form:

# passwd sam

New password:*******

Re-enter new password:*******

How to change the user name under Linux so that the owners and group names of all original folders

1. "Linux chmod command". In the shell, you can use the chown command to change the file owner and user group, and the chgrp command to change the user group where the file is located. In Linux C programs, you can use the chown function to change the file owner and user group.

In addition, in the shell, the current user who wants to modify the file must have administrator root permissions. You can switch to the root user through the su command, or obtain root permissions through sudo.

2. Use the chown command to change the file owner

In the shell, you can use the chown command to change the file owner. The chown command is the abbreviation of change owner. It should be noted that the user must already exist in the system, that is, it can only be changed to the user name recorded in the /etc/passwd file.

The chown command has many uses, and you can also directly modify the name of the user group. In addition, if you want to change the file owner of all subdirectories or files in the directory at the same time, just add the -R parameter.

Basic syntax:

chown [-R] Account name file or directory

chown [-R] Account name: user group name file or directory

parameter:

-R: Make recursive and continuous changes, that is, together with all files and directories under subdirectories

are all updated to become this user group. Often used when changing a certain directory.

Example 1:

[root@localhost home]# touch testfile //File created by root user

[root@localhost home]# ls testfile –l

-rw--w--w- 1 root root 0 Jun 7 19:35 testfile //The owner and owner level of the file are root

[root@localhost home]# chown yangzongde testfile //Modify the file owner to yangzongde

[root@localhost home]# ls testfile -l

-rw--w--w- 1 yangzongde root 0 Jun 7 19:35 testfile //View the file owner is yangzongde, but the group is still root 3. Use the chgrp command to change the user group to which the file belongs

In the shell, you can use the chgrp command to change the user group to which the file belongs. This command is the abbreviation of change group. It should be noted that the user group name to be changed must exist in /etc/group, otherwise an error will be displayed.

Basic syntax:

chgrp [-R] User group name dirname/filename ...

parameter:

-R: Make recursive and continuous changes, that is, together with all files and directories under subdirectories

are all updated to become this user group. Often used when changing a certain directory.

Example 3

[root@localhost home]# ls testfile -l

-rw--w--w- 1 yangzongde root 0 Jun 7 19:35 testfile //View the file owner is yangzongde, but the group is root

[root@localhost home]# chgrp yangzongde testfile //Modify the owner group to yangzongde

[root@localhost home]# ls testfile -l

-rw--w--w- 1 yangzongde yangzongde 0 Jun 7 19:35 testfile

[root@localhost home]# chown root:root testfile // Use chown to modify the owner and group at one time

[root@localhost home]# ls testfile -l

-rw--w--w- 1 root root 0 Jun 7 19:35 testfile

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