passwd

/etc/passwd file

It contains a list of the system’s accounts, giving for each account some useful information like user ID, group ID, home directory, shell, and more.

The /etc/passwd file should have general read permission as many command utilities use it to map user IDs to user names. However, write access to the /etc/passwd must only limit for the superuser/root account.

Interpretation

opc:x:1000:1000:Oracle Public Cloud User:/home/opc:/bin/bash
___ _ ____ ____ ________________________ _________ ________
|  | |    |    |                        |         |        
|  | |    |    |                        |         |        
|  | |    |    |                        |         |        
|  | |    |    |                        |         |        
|  | |    |    |                        |         |        
1  2 3    4    5                        6         7

Username: It is used when user logs in. It should be between 1 and 32 characters in length.
Password: An x character indicates that encrypted password is stored in /etc/shadow file. Please note that you need to use the passwd command to computes the hash of a password typed at the CLI or to store/update the hash of the password in /etc/shadow file.
User ID (UID): Each user must be assigned a user ID (UID). UID 0 (zero) is reserved for root and UIDs 1-99 are reserved for other predefined accounts. Further UID 100-999 are reserved by system for administrative and system accounts/groups.
Group ID (GID): The primary group ID (stored in /etc/group file)
User ID Info (GECOS): The comment field. It allow you to add extra information about the users such as user’s full name, phone number etc. This field use by finger command.
Home directory: The absolute path to the directory the user will be in when they log in. If this directory does not exists then users directory becomes /
Command/shell: The absolute path of a command or shell (/bin/bash). Typically, this is a shell. Please note that it does not have to be a shell. For example, sysadmin can use the nologin shell, which acts as a replacement shell for the user accounts. If shell set to /sbin/nologin and the user tries to log in to the Linux system directly, the /sbin/nologin shell closes the connection.

Example output

cat /etc/passwd

rcamaril:x:51035:2147483646:Roberto Camarillo:/home/rcamaril:/bin/bash
mimigonz:x:52060:2147483646:Miguel Gonzalez:/home/mimigonz:/bin/bash
abkhalid:x:52600:2147483646:Abdul Khalid:/home/abkhalid:/bin/bash
opc:x:1000:1000:Oracle Public Cloud User:/home/opc:/bin/bash
hostmetrics:x:992:99::/home/hostmetrics:/bin/false
oracle-cloud-agent:x:997:994:Oracle Cloud Agent Service User:/var/lib/oracle-cloud-agent:/usr/sbin/nologin