Centos список пользователей ssh

Как посмотреть список пользователей Linux

Привет всем любителям и почитателям альтернативных операционных систем! Я, конечно, чаще всего работаю в Windows, но и с «Пингвином» приходится довольно часто общаться. Недавно мне понадобилось посмотреть список пользователей из старенького файлового сервера на Ubuntu Linux чтобы завести их всех на новом, более мощном под управлением CentOS. Старый уже практически отжил своё и вот-вот должен накрыться, но пока ещё запускается.
Итак, чтобы вывести список пользователей Линукс в консоли, достаточно просто вывести содержимое системного файла

Делается это с помощью команды:

Чтобы исключить из списка системные учётные записи и вычленить только несистемные логины, воспользуйсь вот таким вариантом:

Если полная информация не нужна и достаточно всего лишь логинов, то лучше использовать вот такую команду:

Вот результат её вывода:

Мне именно такой вариант был удобнее, потому как я просто скопировал его и вставил в лист Excel, получив в каждой строчке по логину.

Есть и ещё один неплохой вариант получить список пользователей Linux (Ubuntu, Fedora, CentOS и т.д.) в консоли — это утилита getent . Она используется для того, чтобы выполнить чтение информации по базам данных операционной системы и вывести результат поиска. Команда будет выглядеть так:

Результат выполнения будет таким:

И ещё! Иногда надо посмотреть список активных пользователей Linux, то есть тех, которые сейчас залогинен в системе. Для этого надо воспользоваться другой командой:

Этим Вы вызовите системную утилиту users, которая перечислит все текущие логины, которые подключились к системе в отсортированном по имени виде.
Альтернативным вариантом может служить команда:

То есть Вы увидите таблицу, где будут отображены все виртуальные консоли с залогиненными в них юзерами.

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How To List Users in CentOS 7

Adding a user in CentOS is a common task for most Linux admins. Users have unique username’s and occasionally you may wonder if a username is in use or need other details about the user (like their group ID). We’ll show you how to see a list of users after logging into your Liquid Web CentOS 7 server. Once you’ve logged in via SSH, you’ll be able to run the commands below and get the information you need. Let’s get started!

To get a simple list of usernames, enter the command below and press Enter.

This command gives us a list of users assigned to this CentOS server including system users like:

• root
• daemon
• operator
• sshd
• systuser
• cpanel
• clamav
• dovecot

The getent command is also a common method to look up user details as it pulls info from the passwd, group and other databases that stores the users information. The databases it searches in are:

• ahosts
• ahostsv4
• ahostsv6
• aliases
• ethers (Ethernet addresses)
• group
• gshadow
• hosts
• netgroup
• networks
• passwd
• protocols
• rpc
• services
• shadow.

To search for a specific service noted in the services database, the following command lists the service currently running on port 22:

The getent hosts command lists the recognized hosts:

If you’d like a more detailed list of users, you can use the command below. Using this command will provide you with the username, UID, GID, User Details, their home directory path, and the Default Shell type for the user.

In this example above, you’ll see each field is separated by colons. Lets breakdown the sections to provide more information on the user.

• Username — the user example is root. Other users include bin, daemon, systemd-network, among many others. These are for when these entities need to access the system.
• Password — indicated by the letter x, you can also find this encrypted password in the /etc/shadow file.
• UID — this is the user’s ID, indicated by number starting at 1000. The root user is special as its UID is 0.
• GID — like the user ID, the group ID shows us the group that a user belongs to. The GID also starts at 1000 and for the root users, the group number is 0.
• User Details — usually you’ll find the user’s first name. Sometimes this field can also be left blank.
• Home Directory — this is the path that a user is in when logging into the server. You can alter this path by chroot’ing a user’s path.
• Default Shell — A shell allows for an environment where users interact with the server and the type of shell assigned allows for different usage. The /bin/bash shell allows for text files to run commands.

For a quick overview of usage options, use the — -usage flag:

Full Options:

• -s service, —service service: This flag overrides all the databases with the specified service.
• —s database:service, —service The database:service flag overrides only the specified databases with the specified service. The option may be used multiple times, but only the last service for each of the databases will be utilized.
• -i, —no-idn: This flag disables the IDN encoding in the lookups for ahosts and getaddrinfo (3)
• -?, —help: This flag prints a usage summary and then exits.
• —usage: This flag prints a short summary of usage examples.
• -V, —version: This flag prints the version number, license, and the warranty disclaimer for getent.

Exit Status:

Any one of the following exit values can be utilized to return info by getent:

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How to List Users on CentOS

In this article, I will show you how to list users on CentOS 7. Let’s get started.

The /etc/passwd File:

The users details are stored in /etc/passwd file on CentOS operating system. This is a plain text file. So you can read that with less or cat command as follows:

As you can see, a list of all the users is printed. Information about a single user is stored in a single line /etc/passwd file. Each line contains a lot of information about that specific users separated by colon (:)

A line in the /etc/passwd file contains the following information separated by colon (:)

Username : Password : UID : GID : User Details : Home Directory Path : Default Shell

Here, Username – The login name of the user. It can’t have spaces and other special characters. Only alpha-numeric characters are allowed.

Password – On Linux based operating system such as CentOS the password is stored on /etc/shadow file. If the password is set, x is stored in this field.

UID – On Linux based operating systems, each user has an alphanumeric name or Username and a numeric ID which is called User ID or UID. For ordinary users, the UID starts from 1000. The root user has the UID 0.

GID – On Linux based operating systems, each group has a group name and a numeric ID which is called Group ID or GID. On Linux, every user must be a member of at least one group. So for each user created, a group is also created with the same name as the user name. The user is then added to the group. In this field, the GID of the primary group is added. Primary group is the default group of the user. If a user is a member of many groups, he/she can change it while he/she is logged in with newgrp command. The GID for the ordinary groups starts at 1000. If your Linux system is not specifically configured, the GID should be the same as the UID. The root group has the GID 0.

User Details – This field keeps full name and other personal information about the user as comma separated list. The most common use of this field is to set the Full Name of the user. Just type in the Full Name of your username here and it should be set.

Home Directory Path – This field keeps the path to a directory where all the user files will be stored. The $HOME shell variable is set from this field.

Default Shell – On Linux based operating systems, you must have a shell set for your user. By default, the sh (/bin/sh) and bash (/bin/bash) shell should be set for ordinary users who are able to log in to the system . But there are other shells such as zsh, csh etc. The system users has /sbin/nologin shell set, so they won’t be able to log into the system. If you want to disable login for some user, just set this field for these users to /sbin/nologin.

You can get the same information as it is in the /etc/passwd file with the following command:

Output of the getent password:

Extracting only List of Username from /etc/passwd File:

The /etc/passwd file has a lot of information. If you want to extract only the username from the colon(:) separated list, then you can use awk or cut command to do that.

You can run the following command to extract the login name or username using the cut command:

As you can see, all the usernames are extracted.

You can do the same thing with awk as follows:

As you can see, I get the same output.

Listing Users that Can Login to the System:

If you want to list all the users that can login to your CentOS operating system, then run the following command:

As you can see, only 4 users of my CentOS machine are able to log in and other users are system users. They can’t log in to the system.

So that’s how you list users on CentOS. Thanks for reading this article.

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How do I find out the recent SSH logins for Centos and their IP address?

It seems someone logged into my dev server with root password and did a whole bunch of destruction. How do I check the recent logins and their IP address on Cent OS ?

4 Answers 4

lastlog(8) will report the most recent information from the /var/log/lastlog facility, if you have pam_lastlog(8) configured.

aulastlog(8) will make a similar report, but from the audit logs in /var/log/audit/audit.log . (Recommended, as auditd(8) records are harder to tamper with than syslog(3) records.)

ausearch -c sshd will search your audit logs for reports from the sshd process.

last(8) will search through /var/log/wtmp for the most recent logins. lastb(8) will show bad login attempts .

/root/.bash_history might contain some details, assuming the goober who fiddled with your system was incompetent enough to not remove it before logging out.

Make sure you check

/.ssh/authorized_keys files for all users on the system, check crontab s to make sure no new ports are scheduled to be opened at some point in the future, etc. While you really should just rebuild the machine from scratch, it wouldn’t hurt to take the time to learn what the attacker did.

Note that all logs stored on the local machine are suspect; the only logs you can realistically trust are forwarded to another machine that wasn’t compromised. Perhaps it would be worth investigating centralized log handling via rsyslog(8) or auditd(8) remote machine handling.

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How To List Users in CentOS 7?

by Sushali Dasan | Dec 22, 2020

How To List Users in CentOS 7?

Listing users in CentOS 7 is commonly done before adding a new user or checking if a user already exists.

At Bobcares we often come across this for servers with CentOS7 as a part of our Server Management Services.

Today let’s see how our Support Engineers handle this with a few easy steps.

Commands used to list users in CentOS 7

The following commands are used by our Support engineers to list users in CentOS.

First, we have to log in via SSH, then we can run the commands below and get the information you need.

1. To get a simple list of usernames.

Enter the command given below:

This command gives us a list of users assigned to this CentOS server including system users like:

daemon

operator

sshd

systuser

cpanel

clamav

dovecot

[Need further assistance? We are here for you!]

2. The getent command.

This command will also list user details as it pulls info from the passwd, group and other databases that stores the users information.

The databases used in searches in are:

ahostsv4

ahostsv6

aliases

ethers (Ethernet addresses)

group

gshadow

hosts

netgroup

networks

passwd

protocols

rpc

services

shadow

a) To search for a specific service noted in the services database

The following command lists the service currently running on port 22:

We can check with the port number of the service we wish to see.

b) The getent hosts command lists the recognized hosts:

c) To get a more detailed list of users, we can use the command below.

Using this command will provide you with the username, UID, GID, User Details, their home directory path, and the Default Shell type for the user.

We are using ‘root’ as the user along with the command.

[Need further assistance? We are here for you!]

Conclusion

In this article, we discussed how to list users in CentOS 7. Also, we saw the simple methods that our Support Engineers use to list the users easily.

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