chpasswd - Unix, Linux Command


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NAME

chpasswd - update passwords in batch mode

SYNOPSIS

chpasswd [options]

DESCRIPTION

The chpasswd command reads a list of user name and password pairs from standard input and uses this information to update a group of existing users. Each line is of the format:

user_name:password

By default the supplied password must be in clear-text, and is encrypted by chpasswd. Also the password age will be updated, if present.

The default encryption algorithm can be defined for the system with the ENCRYPT_METHOD variable of /etc/login.defs, and can be overwiten with the -e, -m, or –c options.

chpasswd first update the password in memory, and then commit all the changes to disk if no errors occured for any users.

This command is intended to be used in a large system environment where many accounts are created at a single time.

 

OPTIONS

TAG DESCRIPTION
-c, --crypt-method Use the specified method to encrypt the passwords. The available methods are DES, MD5, NONE, and SHA256 or SHA512 if your libc support these methods.
-e, --encrypted Supplied passwords are in encrypted form.
-h, --help Display help message and exit.

 

-m, --md5 Use MD5 encryption instead of DES when the supplied passwords are not encrypted.
-s, --sha-rounds Use the specified number of rounds to encrypt the passwords.

The value 0 means that the system will choose the default number of rounds for the crypt method (5000).

A minimal value of 1000 and a maximal value of 999,999,999 will be enforced.

You can only use this option with the SHA256 or SHA512 crypt method.

By default, the number of rounds is defined by the SHA_CRYPT_MIN_ROUNDS and SHA_CRYPT_MAX_ROUNDS variables in /etc/login.defs.

EXAMPLES

EXAMPLE-1:

To set passwords for users from the command line, type:

# chpasswd

Followed by entering username:password pairs, one pair per line. Enter CTRL+D when finished.

user1:passwd1
user2:passwd2
CTRL+D

EXAMPLE-2:

To set passwords for users contained in a file named mypwdfile, type the following:

# cat mypwdfile | chpasswd

Note that mypwdfile must contain username:password pairs; one pair per line. For example:

user1:passwd1

user2:passwd2 ...

EXAMPLE-3:

To change password using another encryption method:

# chpasswd -ec MD5

Now MD5 encrypted passwords must be given.

You can use SHA512 as your  encryption algorithm as well.

 

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