This post will guide you how to list all users and groups in your current Linux system. How do I show all user account in Ubuntu/CentOS Linux. How to search for a given user name in Linux.
List All Users
If you want to List all users in your Linux system, you can cat the content of /etc/passwd file, and it will contain a list of the system’s accounts and other useful information, such as: User ID, Group ID, Home directory.etc. type the following commmand to list all user accounts and its useful information:
# cat /etc/passwd
Or
# less /etc/passwd
Outputs:
devops@devops-osetc:~/working$ cat /etc/passwd root:x:0:0:root:/root:/bin/bash daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin bin:x:2:2:bin:/bin:/usr/sbin/nologin sys:x:3:3:sys:/dev:/usr/sbin/nologin sync:x:4:65534:sync:/bin:/bin/sync games:x:5:60:games:/usr/games:/usr/sbin/nologin man:x:6:12:man:/var/cache/man:/usr/sbin/nologin lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin mail:x:8:8:mail:/var/mail:/usr/sbin/nologin news:x:9:9:news:/var/spool/news:/usr/sbin/nologin uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin proxy:x:13:13:proxy:/bin:/usr/sbin/nologin www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin backup:x:34:34:backup:/var/backups:/usr/sbin/nologin list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin irc:x:39:39:ircd:/var/run/ircd:/usr/sbin/nologin gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologin nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin systemd-timesync:x:100:102:systemd Time Synchronization,,,:/run/systemd:/bin/false systemd-network:x:101:103:systemd Network Management,,,:/run/systemd/netif:/bin/false systemd-resolve:x:102:104:systemd Resolver,,,:/run/systemd/resolve:/bin/false systemd-bus-proxy:x:103:105:systemd Bus Proxy,,,:/run/systemd:/bin/false syslog:x:104:108::/home/syslog:/bin/false _apt:x:105:65534::/nonexistent:/bin/false messagebus:x:106:110::/var/run/dbus:/bin/false uuidd:x:107:111::/run/uuidd:/bin/false lightdm:x:108:114:Light Display Manager:/var/lib/lightdm:/bin/false whoopsie:x:109:116::/nonexistent:/bin/false avahi-autoipd:x:110:119:Avahi autoip daemon,,,:/var/lib/avahi-autoipd:/bin/false avahi:x:111:120:Avahi mDNS daemon,,,:/var/run/avahi-daemon:/bin/false dnsmasq:x:112:65534:dnsmasq,,,:/var/lib/misc:/bin/false colord:x:113:123:colord colour management daemon,,,:/var/lib/colord:/bin/false speech-dispatcher:x:114:29:Speech Dispatcher,,,:/var/run/speech-dispatcher:/bin/false hplip:x:115:7:HPLIP system user,,,:/var/run/hplip:/bin/false kernoops:x:116:65534:Kernel Oops Tracking Daemon,,,:/:/bin/false pulse:x:117:124:PulseAudio daemon,,,:/var/run/pulse:/bin/false rtkit:x:118:126:RealtimeKit,,,:/proc:/bin/false saned:x:119:127::/var/lib/saned:/bin/false usbmux:x:120:46:usbmux daemon,,,:/var/lib/usbmux:/bin/false devops:x:1000:1000:devops,,,:/home/devops:/bin/bash sshd:x:121:65534::/var/run/sshd:/usr/sbin/nologin mysql:x:122:129:MySQL Server,,,:/nonexistent:/bin/false redis:x:123:130::/var/lib/redis:/bin/false
If you only want to list user names for user list, you can use the cut command or awk command to only print the first field, type:
$ awk -F ':' '{ print $1}' /etc/passwd
Outputs:
devops@devops-osetc:~/working$ awk -F ':' '{ print $1}' /etc/passwd
root
daemon
bin
sys
sync
games
man
lp
mail
news
uucp
proxy
www-data
backup
list
irc
......
If you want to check if one given user name exists in your system, you can use the grep command to check, type:
# grep '^root' /etc/passwd | awk -F ':' '{ print $1}'
Outputs:
devops@devops-osetc:~/working$ grep '^root' /etc/passwd | awk -F ':' '{ print $1}'
root
List All Groups
If you want to list all groups in your Linux system, you can use cat command to print all lists in /etc/group file. This file will contain all group names and its ID information. Type the following command:
# cat /etc/group
Or
# less /etc/group
Outputs:
devops@devops-osetc:~/working$ cat /etc/group root:x:0: daemon:x:1: bin:x:2: sys:x:3: adm:x:4:syslog,devops tty:x:5: disk:x:6: lp:x:7: mail:x:8: news:x:9: uucp:x:10: man:x:12: proxy:x:13: ......
Show Which Linux Users are logged in
If you want to check who is logged on your Linux system, you can execute Who command, type:
# who
outputs:
devops@devops-osetc:~/working$ who devops tty7 2018-12-18 21:27 (:0) devops pts/1 2018-12-18 21:28 (10.182.37.163)