This tutorial shows you how to list users in Linux. You’ll also learn to list only the logged users.
Today different Operating
Systems have the capability to use multiple users, each one with their
settings and custom configurations to make things easier for
administrators and operators to work in together on the same system.
Linux on the other hand is very strong on this matter as it allows
multiple users to work at the same time on the system in an independent
way. It can even allow a single user to open several sessions even from
different locations in order to work on the system.
Here are some hints & tricks to handle users in Linux.
List all the users on Linux
Probably, the very first thing to know is how to know what users are
in my system. There are several ways you can obtain the list of users in
Linux.
1. Show users in Linux using less /etc/passwd
This command allows sysops to list the the users that are locally
stored in the system. It will give the listing in structured way as:
Now if you want to distinguish the normal users from the system users, you can refer to the User ID (UID) number.
Generally,
a normal user has UID greater or equal to 1000. This gives you a hint
that the user with UID >=1000 is a normal user and users with UID
<1000 are="" p="" system="" users.="">
2. View users using getent passwd
This command will give you a similar output as “less /etc/passwd” however, this one actually queries the GNU Name Service Switch functionality configuration file (located at /etc/nsswitch.conf).
This conf includes passwd, so that’s why it will display very similar but if you use LDAP for authentication it will include that as well.
3. List Linux users with compgen
If you just want to list all the usernames without any additional information, you can use the compgen command with -u option.
compgen -u
The output would be like this:
compgen -u
root
daemon
bin
sys
sync
games
man
lp
mail
news
uucp
proxy
www-data
backup
list
irc
gnats
nobody
systemd-network
systemd-resolve
syslog
messagebus
_apt
uuidd
avahi-autoipd
usbmux
dnsmasq
rtkit
cups-pk-helper
speech-dispatcher
whoopsie
kernoops
saned
pulse
avahi
colord
hplip
geoclue
gnome-initial-setup
gdm
abhishek
Tip
You can use compgen
command with -c option to list all the commands available to you. This
is helpful when you are not the admin on a Linux system and don’t have sudo access.
A few tips about listing users in Linux
You just saw three ways to view users in Linux. Here are a few tips that would help you while dealing with the users listing.
List only the usernames
You already have the compgen command for that but you don’t have to remember it all the time.
If we would like to only get a list of the usernames in the system, you can use the awk command or the cut command to filter the output of the other two commands we saw earlier.
cut -d: -f1 /etc/passwd
or
getent passwd | awk -F: '{ print $1}'
Any of these will give us a filtered list of users, showing only the very first column which is username:
root
daemon
bin
sys
sync
games
man
lp
mail
news
johndoe
davmail
statd
Check if a username already exists in the system
This might be useful if you want to know if a particular username already exists in the system:
If you want to know what users are currently logged into your system,
then you need to perform a simple ‘who’ on your command line and this
will immediately list current usernames with an active session to your
system
In this case, the listing will give you not only the list of
usernames connected but also how they are connected, since when they are
connected and from where they are connected.
The very first column will tell you what username is it.
The second column will give you what type of connection it is: if
it’s represented with a “:X” where X is a number, it means it is using a
Graphical User Interface (GUI) or Desktop session such as Gnome, XDE,
etc; if it says “pts/X” where X is a number, it means it’s a connection
made through SSH protocol (command line).
The third column will tell you since when this session has been
connected to the server (date and time). The fourth and last column will
give you the location from where it’s connected, if remote it will
display the IP from where the connection is made if local (like the GUI)
it will display “(:X)” where X is the number of the session in this
case and will match the number in the second column for that row.
Wrapping up
As you can see, listing users in Linux is not difficult at all. It
consists of simple commands which will output all the information for
you, whatever you want to do or obtain of that information is something
you need to filter depending on what you want to check on the system.
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