This setting does not apply to system users, and can be overridden on the command line.

If set to yes, the user will login in the root (/) directory if it is not possible to cd to her home directory.

It can take one of these values: DES (default), MD5, SHA256, SHA512, YESCRYPT. MD5 and DES should not be used for new hashes, see crypt(5) for recommendations.

Note: this parameter overrides the MD5_CRYPT_ENAB variable.

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.

The default value for GID_MIN (resp. GID_MAX) is 1000 (resp. 60000).

useradd and newusers use this to set the mode of the home directory they create.

No LASTLOG_UID_MAX option present in the configuration means that there is no user ID limit for writing lastlog entries.

Note: logging unknown usernames may be a security issue if an user enter her password instead of her login name.

This will most likely be overridden by PAM, since the default pam_unix module has its own built in of 3 retries. However, this is a safe fallback in case you are using an authentication module that does not enforce PAM_MAXTRIES.

The default value is 0, meaning that there are no limits in the number of members in a group.

This feature (split group) permits to limit the length of lines in the group file. This is useful to make sure that lines for NIS groups are not larger than 1024 characters.

If you need to enforce such limit, you can use 25.

Note: split groups may not be supported by all tools (even in the Shadow toolsuite). You should not use this variable unless you really need it.

With a lot of rounds, it is more difficult to brute force 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), which is orders of magnitude too low for modern hardware.

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.

The default values for SUB_GID_MIN, SUB_GID_MAX, SUB_GID_COUNT are respectively 100000, 600100000 and 65536.

The default values for SUB_UID_MIN, SUB_UID_MAX, SUB_UID_COUNT are respectively 100000, 600100000 and 65536.

The default value for SYS_GID_MIN (resp. SYS_GID_MAX) is 101 (resp. GID_MIN-1).

The default value for SYS_UID_MIN (resp. SYS_UID_MAX) is 101 (resp. UID_MIN-1).

TTYGROUP can be either the name of a group or a numeric group identifier.

If TTYGROUP is not defined, then the group ownership of the terminal is set to the user's primary group. If TTYPERM is not defined, then the permissions are set to 0600.

If you have a write program which is "setgid" to a special group which owns the terminals, define TTYGROUP to the group number and TTYPERM to 0620. Otherwise leave TTYGROUP commented out and assign TTYPERM to either 622 or 600.

The default value for UID_MIN (resp. UID_MAX) is 1000 (resp. 60000).

useradd and newusers use this mask to set the mode of the home directory they create if HOME_MODE is not set.

It is also used by pam_umask as the default umask value.

The return code of the script is not taken into account.

Here is an example script, which removes the user's cron, at and print jobs:

#! /bin/sh
# Check for the required argument.
if [ $# != 1 ]; then
	echo "Usage: $0 username"
	exit 1
fi
# Remove cron jobs.
crontab -r -u $1
# Remove at jobs.
# Note that it will remove any jobs owned by the same UID,
# even if it was shared by a different username.
AT_SPOOL_DIR=/var/spool/cron/atjobs
find $AT_SPOOL_DIR -name "[^.]*" -type f -user $1 -delete \;
# Remove print jobs.
lprm $1
# All done.
exit 0

With a high cost factor, it is more difficult to brute force the password. But note also that more CPU resources will be needed to authenticate users.

The value must be inside the 1-11 range.

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.