how to Restrict particular user from Loging in multiple times

[Soujanya]

Hi All,

How do I write a script that doesn't permit some users to log in more than once. It looks up a configuration file which contains a list of those users, one user per line. Where should I place the script code?

Any Help is much appreciated :)

Thanks in Advance
Soujanya.R

[Ivan Ferreira · Accepted solution]

You have two options:

Configure the maxlogins option in /etc/security/limits.conf

Create a shell script and add it to the /etc/profile:

# Maxlogins
# Version 1.2
# Registro de cambios
# Version 1: Primera version estable
# Version 1.1: Se agrego la opcion -a al comando who y grep -v "x " para evitar informacion falsa
# Version 1.2: Se agrego ^ al grep para permitir comentar entradas en el archivo de configuracion

MAXDEFAULT=`awk '$1 == "MAXDEFAULT" { print $2 }' /etc/security/maxlogins.conf`

USRSESLIMIT=`grep -w "^$USER" /etc/security/maxlogins.conf | awk '{ print $2}'`

if [ -z "$USRSESLIMIT" ] ; then
USRSESLIMIT=$MAXDEFAULT;
fi

if [ "$USRSESLIMIT" -eq 0 ]; then
echo "Limites de sesion no establecidos"
else
SESCOUNT=`who -a | grep $USER | grep -v "x "| wc -l`
if [ $SESCOUNT -gt $USRSESLIMIT ]; then
echo "Ha alcanzado el limite de sesiones establecido"
echo "Presione ENTER para salir"
# Evitamos que pueda cancelar el script
stty dsusp undef eof undef eol undef eol2 undef erase undef discard undef \
status undef intr undef kill undef lnext undef quit undef reprint undef \
start undef stop undef susp undef werase undef
read
exit
else
echo "INFORMACION: Usted tiene $SESCOUNT sesiones abiertas"
fi
fi


The /etc/security/maxlogins.conf file will look like this:

# Valor por defecto. 0 = ilimitado
MAXDEFAULT 1

# Configuracion por usuario
# Superusuario
root 0
#
# Usuarios
#
user1 3
user2 5
user3 1

[Atul Gautam]

Soujanya,

Also there is a module in PAM which is called as "pam_tally.so" which is again used for restricting users/attackers.

Also go through the URL ---

http://sial.org/howto/linux/pam_tally/

Beside this, I am attaching a PDF doc for your reference purpose.




Atul