From the command line try:
For a lot of reasons it is a really, really bad idea to try to exceed this value:
applications using (_POSIX_)LOGIN_NAME_MAX for usernames will segfault.
LDAP will not work.
Other PAM schemes will not work.
OpenSSH protocol 1 will fail with overlong usernames.
/etc/rhosts won't work for users on your box connecting to remote boxes
I don't think anything good will come from this but try editing /etc/default/login.defs.
CentOS follows Red Hat useradd conventions, see: /etc/default/useradd
I have been told that my college wants to implement LDAP. This creates a problem for me because my users active directory names and email user names differ from their unix system logins. Is there any way to make the Unix usernames more compliant to my user's other account usernames??? We use... (1 Reply)
Hi all,
I tried to write a shell to read huge file and eliminate max length record which is wrong generated record. But I get an error
remove_sp.sh: line 27: syntax error near unexpected token `else'
remove_sp.sh: line 27: ` else $LINE >> REJFILE'
My shell is here:
#!/bin/sh... (5 Replies)
Hi all,
I have a flat file of 1000 rows. I want to check the length of the 5th column. The one having the longest length , I want to set it as DEFINED PARAMETER.
So later I can check others with that particular number only.
Any ideas ?? (2 Replies)
Hi,
I need to create a file of record length more than 300 characters.
But in my unix box, i am able to create a file only with a maximum of 256 characters per record.
Is there anyway i can create a file with more than 300 characters in this case?
Or How to increase the maximum record... (1 Reply)
Hello All,
I am using RHEL 4. Currently maximum password length limit is set to 8 on my system.
Please tell what do i need to change to increase this limit to say 20. I changed the login.defs and included the following line -
"
PASS_MAX_LEN 20
"
but this dint work.
I further... (7 Replies)
Hi
I want to know the maximum length of user name under NIS? I tried googling but it didnt help :(. If there is any command to find out this please let me know. I know on unix user name should be 8 characters long but just i want to know if i can have 9 letter user under mapped under NIS. (1 Reply)
Hello,
In shared memory, when using shmget function, first parameter is ket_t key.
I know it is an integer type, but length of it is system dependent. That means may not be have integer's ranges.
What is range of key_t in Linux? Is it different in distros, for example in ubuntu & fedora? (2 Replies)
Hey Any one...
Do u know any way I can modify the max username length in unix? I guess it is 32/64 characters by default. Suppose I want to increase it to 128.
i hav tried /etc/skel
but no use...
How can I do that? (2 Replies)
Discussion started by: MayureshRisbud
2 Replies
LEARN ABOUT XFREE86
chpasswd
CHPASSWD(8) System Management Commands CHPASSWD(8)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 passwords must be supplied in clear-text, and are encrypted by chpasswd. Also the password age will be updated, if present.
By default, passwords are encrypted by PAM, but (even if not recommended) you can select a different encryption method with the -e, -m, or
-c options.
Except when PAM is used to encrypt the passwords, chpasswd first updates all the passwords in memory, and then commits all the changes to
disk if no errors occurred for any user.
When PAM is used to encrypt the passwords (and update the passwords in the system database) then if a password cannot be updated chpasswd
continues updating the passwords of the next users, and will return an error code on exit.
This command is intended to be used in a large system environment where many accounts are created at a single time.
OPTIONS
The options which apply to the chpasswd command are:
-c, --crypt-method 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.
By default, PAM is used to encrypt the passwords.
-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.
-R, --root CHROOT_DIR
Apply changes in the CHROOT_DIR directory and use the configuration files from the CHROOT_DIR directory.
-s, --sha-rounds 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.
CAVEATS
Remember to set permissions or umask to prevent readability of unencrypted files by other users.
CONFIGURATION
The following configuration variables in /etc/login.defs change the behavior of this tool:
SHA_CRYPT_MIN_ROUNDS (number), SHA_CRYPT_MAX_ROUNDS (number)
When ENCRYPT_METHOD is set to SHA256 or SHA512, this defines the number of SHA rounds used by the encryption algorithm by default (when
the number of rounds is not specified on the command line).
With a lot of rounds, it is more difficult to brute forcing the password. But note also that more CPU resources will be needed to
authenticate users.
If not specified, the libc will choose the default number of rounds (5000).
The values must be inside the 1000-999,999,999 range.
If only one of the SHA_CRYPT_MIN_ROUNDS or SHA_CRYPT_MAX_ROUNDS values is set, then this value will be used.
If SHA_CRYPT_MIN_ROUNDS > SHA_CRYPT_MAX_ROUNDS, the highest value will be used.
Note: This only affect the generation of group passwords. The generation of user passwords is done by PAM and subject to the PAM
configuration. It is recommended to set this variable consistently with the PAM configuration.
FILES
/etc/passwd
User account information.
/etc/shadow
Secure user account information.
/etc/login.defs
Shadow password suite configuration.
/etc/pam.d/chpasswd
PAM configuration for chpasswd.
SEE ALSO passwd(1), newusers(8), login.defs(5), useradd(8).
shadow-utils 4.5 01/25/2018 CHPASSWD(8)