Linux list all users account using the /etc/passwd file
In order to list all users on Linux, use the cat command as follows: $ cat /etc/passwd Here is what I see:
Each line in the file has seven fields as follows. For example, consider the following line: vnstat:x:131:137:vnstat daemon. /var/lib/vnstat:/usr/sbin/nologin Where,
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vnstat – The user name or login name.
x – Encrypted password is stored in the /etc/shadow file.
131 – UID (user ID number)
137 – Primary GID (group ID number)
vnstat daemon – GECOS. It may includes user’s full name (or application name, if the account is for a program), building and room number or contact person, office telephone number, home telephone number and any other contact information.
/var/lib/vnstat – Home directory for the user.
/usr/sbin/nologin – Login shell for the user. Pathnames of valid login shells comes from the /etc/shells file.
How to list users in Linux using pagers
Of course we can use pagers such as more/less commands as follows to view the /etc/passwd file: $ more /etc/passwd $ less /etc/passwd Sample outputs:
Fig.01: List users using /etc/passwd
Linux list user names only
To list only usernames type the following awk command: $ awk -F’:’ ‘< print $1>‘ /etc/passwd Sample outputs:
Another option is to use the cut command: $ cut -d: -f1 /etc/passwd
Get a list of all users using the getent command
To get a list of all Linux users you can type the following getent command: $ getent passwd $ getent passwd | grep tom ## get a list all users ## $ getent passwd | cut -d: -f1 ## count all user accounts using the wc ## $ getent passwd | wc -l One can use the compgen command on Linux to list users and other resources too: $ compgen -u
Find out whether a user account exists in the Linux server
We can use above commands to see whether a user exists in the Linux machine as follows using the grep command:
A simplified command would be:
How to count user accounts in the Linux server
Want to get user accounts count on your system? Try the wc command as follows: $ compgen -u | wc -l $ getent passwd | wc -l
A Note About System and General Users
Each user has numerical user ID called UID. It is defined in /etc/passwd file. The UID for each user is automatically selected using /etc/login.defs file when you use useradd command. To see current value, enter: $ grep «^UID_MIN» /etc/login.defs $ grep UID_MIN /etc/login.defs Sample outputs:
1000 is minimum values for automatic uid selection in useradd command. In other words all normal system users must have UID >= 1000 and only those users are allowed to login into system if shell is bash/csh/tcsh/ksh etc as defined /etc/shells file. Type the following command to list all login users:
To see maximum values for automatic uid selection in the useradd command, enter: $ grep «^UID_MAX» /etc/login.defs Sample outputs:
In other words, all normal system users must have UID >= 1000 (MIN) and UID /etc/shells file. Here is an updated code to get details:
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Как посмотреть пользователей Ubuntu
Иногда возникает необходимость посмотреть всех зарегистрированных в системе Linux пользователей. Например, для того чтобы узнать не зарегистрирован ли кто лишний в системе, или изменить данные/группу одного из пользователей.
Профессионалы, конечно, же знают как это делается, причем кучей способов, а вот для новичков это может стать проблемой. В этой статье я покажу как посмотреть список пользователей Ubuntu несколькими способами — с помощью терминала и графических утилит.
Как посмотреть список пользователей в терминале
Сперва рассмотрим как посмотреть пользователей ubuntu в терминале Linux, так как это наиболее универсальный способ, который работает почти во всех дистрибутивах. В операционной системе Linux есть специальный файл в котором хранится информация обо всех пользователях. Это /etc/passwd. Записи в файле имеют следующий синтаксис:
имя_пользователя пароль ид ид_группы группа домашний_каталог оболочка
Надо заметить, что вместо пароля теперь записывается буква X это было сделано для безопасности. Все пароли пользователей хранятся теперь в другом файле. Остается только набрать команду и вы узнаете список пользователей linux:
Пользователи с ID меньше 1000 — системные, они были созданы во время установки некоторых сервисов для более безопасной их работы. Этих пользователей трогать не следует. В этом примере в системе вручную зарегистрирован только один пользователь — Sergiy.
В файле /etc/passwd слишком много лишних данных, если вам нужны только имена пользователей, можно отфильтровать вывод:
sed ‘s/:.*//’ /etc/passwd
Так вы можете посмотреть всех пользователей Ubuntu. С зарегистрированными пользователями разобрались. Но намного интереснее посмотреть какие пользователи сейчас активны в системе, и какие команды они выполняют. Для этого есть утилита w:
Здесь выводятся все выполняемые пользователями команды. Если пользователь сейчас выполняет в терминале несколько команд, то будет отображено два пункта для одного пользователя.
Кроме того, вы можете посмотреть историю входов пользователей в систему. Для этого есть команда last, она выводит информацию на основе лога /var/wtmp:
Дату последнего входа для каждого пользователя вы можете посмотреть с помощью команды lastlog:
Если пользователь никогда не входил, команда так и скажет, в противном случае мы увидим дату последнего входа.
Список пользователей в GUI
В Ubuntu зарегистрированными в системе пользователями можно управлять с помощью параметров системы. Откройте утилиту и выберите в самом низу пункт Учетные записи. Здесь уже не будут отображаться системные пользователи. В панели слева — непосредственно сам список, а справа можно изменить данные и настройки:
Для KDE есть более интересная утилита управления пользователями — KUser:
Здесь так же как и в терминале отображены все пользователи, в том числе системные. Можно менять различные данные, в том числе пароли, основную и дополнительную группы и т д.
Как видите, только в терминале вы можете посмотреть более подробную информацию, проверить даты входа и точно узнать не используют ли систему другие люди.
Выводы
Теперь вы знаете как посмотреть список пользователей Ubuntu. Это не очень сложно, но нужно только понять основы того как это работает. Если у вас остались вопросы, спрашивайте в комментариях!
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15+ examples for listing users in Linux
In this post, you will learn about listing users in Linux. Besides this, you will know other tricks about Linux users’ characteristics.
There are two types of users in Linux, system users who are created by default with the system. On the other hand, there are regular users who are created by system administrators and can log in to the system and use it.
Table of Contents
What file contains the list of the users on Linux?
Before we start listing users, we need to know where these users saved on Linux?
The users are stored in a text file on the system called the passwd file. This file is located in the /etc directory.
The file is located on the following path:
In this file, you can find all the information about the users in the system.
List all users
Listing users is the first step to manage them. This way, we will know how many they are and who they are. In Linux, almost everything can be done in various ways, and this is no exception.
To list all users, you can use the cat command:
As you can see in the image, there is all the information about the users.
1- In the first field, you will see the user name.
2- The second field (The x character) is a representation of the encrypted password. The encrypted password is stored in /etc/shadow file.
3- The UID or the user ID.
4- The next field refers to the primary group of the user.
5- Then, it shows user ID info such as the address, email, etc.
6- After this, you will see the home directory of the user.
7- The last field is the shell used by that user.
However, although the information is quite useful, if you only want to list users’ names in a basic way, you can use this command:
Now we have the names only by printing the first field of the file only.
List & sort users by name
The above command serves the purpose of listing users on Linux. But what about listing the users in alphabetical order?
To do this, we will use the previous command, but we will add the sort command.
So, the command will be like this:
As you can see in the image, the users are shown sorted.
Linux list users without password
It is important to know users who have no password and to take appropriate action. To list users who do not have a password, just use the following command:
The used regex will list all users with no password.
List users by disk usage
If you have a big directory and you want to know which user is flooding it, you can use the du command to get the disk usage.
With this, you can detect which of these users are misusing the disk space.
For it, it is enough to use the following command:
In this way, you will have the users ordered by the disk usage for the /home directory.
We used the -n for the sort command to sort the output by numbers.
List the currently logged users
To list the currently logged in users, we have several ways to do it. The first method we can use the users command:
It will list the users with open sessions in the system.
But this information is a little basic; however, we have another command that gives more details. The command is simply w.
With this command, we can have more information, such as the exact time when the session was started and the terminal session he has available.
Finally, there is a command called who. It is available to the entire Unix family. So you can use it on other systems like FreeBSD.
With who command, we also have some information about currently logged in users. Of course, we can add the option -a and show all the details.
This way, you know everything about the logged in users.
Linux list of users who recently logged into the system
We saw how to get the currently logged in users, what about listing the login history of users?
You can use the last command to get more info about the logins that took place:
Or the logins of a particular user
These are the user login activity and when it was started and how long it took.
List users’ logins on a specific date or time
What about listing users’ logins on a specific date or time? To achieve this, we use the last command but with the -t parameter:
And now, all you have to do is choose an exact date & time to list who logged at that time.
List all users in a group
There are two ways to list the members of a group in Linux, the easiest and most direct way is to get the users from the /etc/group file like this:
This command will list users in the likegeeks group.
The other way is by using commands like the members command in Debian based distros. However, it is not installed by default in Linux distributions.
To install it in Ubuntu / Linux Mint 19, just use APT:
Or in the case of CentOS:
Once it’s installed, you can run the command then the name of the group you want to list the users to:
This way, you can list users for a group in a Debian based distro. What about a RedHat based distro like CentOS?
You can use the following command:
List users with UID
In Unix systems, each user has a user identifier or ID. It serves to manage and administer accounts internally in the operating system.
Generally, UIDs from 0 to 1000 are for system users. And thereafter for regular users. Always on Unix systems, UID zero belongs to the root users (You can have more than one user with UID of zero).
So now, we will list the users with their respective UID using Awk.
The command that performs the task is the following:
As you can see, each user with his UID.
List root users
In a Unix-like system like Linux, there is usually only one root user. If there are many, how to list them?
To do this, we can use this command:
Here we are filtering the file to get users with UID of zero (root users).
Another way by checking the /etc/group file:
Here we are getting users in the group root from the /etc/group file.
Also, you can check if any user can execute commands as root by checking the /etc/sudoers file:
Get the total number of users
To get the total number of users in Linux, you can count lines in /etc/passwd file using the wc command like this:
Great! 43 users. But this includes system and regular users. What about getting the number of regular users only?
Easy! Since we know from above that regular users have UID of 1000 or greater, we can use Awk to get them:
List sudo users
Linux systems have a utility called sudo that allows you to execute commands as if you were another user who is usually the root user.
This should be handled with care in a professional environment.
Also, it is very important to know which users can run the sudo command. For this, it is enough to list the users that belong to the sudo group.
Users in this group can execute commands as super users.
List users who have SSH access
SSH allows users to access remote computers over a network. It is quite secure and was born as a replacement for Telnet.
By default, all regular users can log in and use SSH. If you want to limit this, you can use the SSH configuration file (/etc/ssh/ssh_config) and add the following directive:
Also, you can allow groups instead of allowing users only using the AllowGroups directive:
These directives define who can access the service. Don’t forget to restart the SSH service.
List users who have permissions to a file or directory
We can give more than one user permission to access or modify files & directories in two ways.
The first method is by adding users to the group of the file or the directory.
This way, we can list the group members using the members utility as shown above.
Okay, but what if we just want this user to have access to this specific file only (Not all the group permissions)?
Here we can set the ACL for this file using setfacl command like this:
Here we give the user called newser the permission for the file called myfile the permissions of read & write & execute.
Now the file can be accessed or modified by the owner, and the user called newuser. So how to list them?
We can list them using the getfacl command like this:
This command will list all users who have permissions for the file with their corresponding permissions.
List locked (disabled) users
In Linux, as a security measure, we can lock users. This as a precaution if it is suspected that the user is doing things wrong, and you don’t want to completely remove the user and just lock him for investigation.
To lock a user, you can use the following command:
Now the user named myuser will no longer be able to login or use the system.
To list all locked users of the system, just use the following command:
This will print all locked users, including system users. What about listing regular users only?
As we saw above, using Awk, we can get locked regular users like this:
Listing remote users (LDAP)
Okay, now can list all system users (local users), but what about remote users or LDAP users? Well, we can use a tool like ldapsearch, but is there any other way?
Luckily yes! You can list local & remote users with one command called getent
This command lists both local system users and LDAP or NIS users or any other network users.
You can pipe the results of this command to any of the above-mentioned commands the same way.
Also, the getent command can list group accounts like this:
You can check the man page of the command to know the other databases the command can search in.
Conclusion
Listing users in the Linux system was fun! Besides this, we have learned some tips about users and how to manage them in different ways.
Finally, this knowledge will allow a better administration of the users of the system.
I hope you find the tutorial useful. Keep coming back.
