En linux no hay ningún comando para saber el número de usuarios activos en el sistema. Pero dicha información la podemos sacar mirando cierto ficheros como /etc/passwd

Para sacar un listado de usuarios

cat /etc/passwd | grep -v nologin

También para entornos con LDAP podemos usar

getent passwd |egrep -v ‘nologin|false’

También podemos ejecutar el siguiente script para ver cuales son usuarios creados por el sistema

#!/bin/bash
# Name: listusers.bash
# Purpose: List all normal user and system accounts in the system. Tested on RHEL / Debian Linux
# Author: Vivek Gite <www.cyberciti.biz>, under GPL v2.0+
# -----------------------------------------------------------------------------------
_l="/etc/login.defs"
_p="/etc/passwd"
 
## get mini UID limit ##
l=$(grep "^UID_MIN" $_l)
 
## get max UID limit ##
l1=$(grep "^UID_MAX" $_l)
 
## use awk to print if UID >= $MIN and UID <= $MAX and shell is not /sbin/nologin   ##
echo "----------[ Normal User Accounts ]---------------"
awk -F':' -v "min=${l##UID_MIN}" -v "max=${l1##UID_MAX}" '{ if ( $3 >= min && $3 <= max  && $7 != "/sbin/nologin" ) print $0 }' "$_p"
 
 
 
echo ""
echo "----------[ System User Accounts ]---------------"
awk -F':' -v "min=${l##UID_MIN}" -v "max=${l1##UID_MAX}" '{ if ( !($3 >= min && $3 <= max  && $7 != "/sbin/nologin")) print $0 }' "$_p"

Listado tipo tabla

#!/bin/bash
# Name: listusers.bash
# Purpose: List all normal user and system accounts in the system. Tested on RHEL / Debian Linux
# Author: Vivek Gite , under GPL v2.0+
# http://www.cyberciti.biz/faq/linux-list-users-command/
# ———————————————————————————–
_l=”/etc/login.defs”
_p=”/etc/passwd”
 
## get mini UID limit ##
l=$(grep “^UID_MIN” $_l)
 
## get max UID limit ##
l1=$(grep “^UID_MAX” $_l)
 
## use awk to print if UID >= $MIN and UID = min && $3 = min && $3 <= max && $7 != "/sbin/nologin" ) printf "%-15s %-5s %-5s %-25s %-10sn", $1, $3, $4, $6, $7 }' "$_p"
 
echo " "
 
## use awk to print if UID $MAX ##
echo “—————————-[ System User Accounts ]—————————”
printf “%-15s %-5s %-5s %-25s %-10sn” “Login” “UID” “GID” “Home” “Shell”
echo “——————————————————————————-”
awk -F':’ -v “min=${l##UID_MIN}” -v “max=${l1##UID_MAX}” ‘{ if ( !( $3 >= min && $3 = min && $3 <= max && $7 != "/sbin/nologin" ) ) printf "%-15s %-5s %-5s %-25s %-10sn", $1, $3, $4, $6, $7 }' "$_p"

Listado de grupos

     #!/bin/bash
    # Name: listgroups.bash
    # Purpose: List all normal user and system groups in the system. Tested on RHEL / Debian Linux
    # Author: Vivek Gite , under GPL v2.0+
    # http://www.cyberciti.biz/faq/linux-list-users-command/
    # ———————————————————————————–
    _l=”/etc/login.defs”
    _g=”/etc/group”
 
    ## get mini GID limit ##
    l=$(grep “^GID_MIN” $_l)
 
    ## get max GID limit ##
    l1=$(grep “^GID_MAX” $_l)
 
    ## use awk to print if GID >= $MIN and GID = min && $3 = min && $3 <= max ) printf "%-15s %-5s %-10sn", $1, $3, $4 }' "$_g"
 
    echo " "
 
    ## use awk to print if GID $MAX ##
    echo “—————————–[ System User Groups ]—————————-”
    printf “%-15s %-5s %-10sn” “Group” “GID” “Logins”
    echo “——————————————————————————-”
    awk -F':’ -v “min=${l##GID_MIN}” -v “max=${l1##GID_MAX}” ‘{ if ( !( $3 >= min && $3 = min && $3 <= max ) ) printf "%-15s %-5s %-10sn", $1, $3, $4 }' "$_g"

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