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Passwd: Usernotknowntotheunderlyingauthentication solves this problem because passwd: Usernotknowntotheunderlyingauthentication is encountered when creating new users for Linux... passwd: User not known to the underlying authentication solves this problem because passwd: User not known to the underlying authentication is encountered when creating a new User for Linux, and finally found the solution. Now we can record the solution to make it easier to remember. When you create a User on www.2cto.com, the following message is displayed: passwd: User not known to the underlying authentication. Google, read the relevant information, and then said pwck, pwconv can solve the problem. So first, I use the pwck command. Pwck is used to check the content in the/etc/passwd account configuration file and whether the actual home directory exists, you can also check whether the content of/etc/passwd/etc/shadow is consistent. In addition, if the data column dislocation in/etc/passwd is incorrect, you will be prompted to revise it. 1 --> $ sudo/usr/sbin/pwckPassword: user adm: directory/var/adm does not existuser news: directory/etc/news does not existuser uucp: directory/var/spool/uucp does not existuser gopher: directory/var/gopher does not existuser ftp: directory/var/ftp does not existuser pcap: directory/var/arpwatch does not existuser avahi-autoipd: directory/var/lib/avahi-autoipd does not existuser oprofile: dir ECloud/home/oprofile does not existuser sabayon: directory/home/sabayon does not existpwck: no changes the above only tells me that these accounts do not have a directory, because most of those accounts are system accounts and do not need home directories, it is a normal error! ', You can use the grpck command for the corresponding group check. Pwck ensures the integrity of system authentication information. pwck checks the following fields of each item: -whether there is a unique user name-whether there is a legal user ID and group ID-whether there is a legal Master group-whether there is a legal home directory-whether there is a legal shell (command interpreter, such as bash) it is vital to check the number of domains in each item and the word of the unique user name. if the number of fields in an item is incorrect, the user will be prompted to delete the entire row. if the user does not have a positive answer, pwck will not continue to check. if a duplicate user name exists, the user will be prompted to delete the item, and pwck will continue to check. other errors only warn users and encourage them to run the usermod command to correct the errors. some commands that operate on the/etc/passwd file. if you cannot modify damaged or repeated items, pwck must perform operations to delete these items. 2 --> $ sudo/usr/sbin/pwconv this command mainly aims to move the account and password in/etc/passwd to/etc/shadow. Medium! 'The early Unix systems did not have/etc/shadow. Therefore, the user's login password was in the second column of/etc/passwd. later, for system security, the password is moved to/etc/shadow. After using pwconv, you can: * Compare/etc/passwd and/etc/shadow. if the account in/etc/passwd does not have the corresponding/etc/shadow password, then pwconv will go to/etc/login. defs uses the relevant password information and creates the/etc/shadow data for this account. * If the encrypted password information exists in/etc/passwd, pwconv moves the password column to/etc/shadow, and changes the password column corresponding to the original/etc/passwd to x! In general, if you normally use useradd to add users, using pwconv will not have any action, because/etc/passwd and/etc/shadow will not have the above two problems! However, if you manually set the account, this pwconv is very important! 3 --> $ sudo passwd *** passwd: all authentication tokens updated successfully. the password is successfully modified!
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