list all users account using the /etc/passwd file

$ cat /etc/passwd

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,

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.

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Of course we can use pagers such as more/less commands as follows to view the /etc/passwd file:

$ more /etc/passwd

it will show how more pages with content are left

$ less /etc/passwd

you can access the file using up and down arrow

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limit outputs using the head command and tail command as follows:

tail -5 /etc/passwd -- show last 5 users

head -5 /etc/passwd -- shows top 5 users

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To list only usernames type the following awk command:

$ awk -F':' '{ print $1}' /etc/passwd

Sample outputs:

root

daemon

bin

sys

sync

games

man

lp

Refer : https://www.cyberciti.biz/faq/linux-list-users-command/

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You need to use rpm command to display all installed packages in Linux.

Red Hat/Fedora Core/CentOS Linux

Type the following command to get list of all installed software

# rpm -qa | less

Debian Linux

Type the following command to get list of all installed software:

# dpkg --get-selections

Ubuntu Linux

Type the following command to get list of all installed software:

# sudo dpkg --get-selections