/etc/passwd file stores essential information, which is required during login i.e. user account information. /etc/passwd is a text file, that contains a list of the system's accounts, giving for each account some useful information like user ID, group ID, home directory, shell, etc. It should have general read permission as many utilities, like ls use it to map user IDs to user names, but write access only for the superuser (root).
Each line in /etc/passwd represents a single user. The first listed is the root (i.e., administrative) account, which has complete power over every aspect of the system. This is followed by system-defined groups and accounts that are required for proper installation and update of system software. The lines at the end represent real people who use the system.
Understanding fields in /etc/passwd
The /etc/passwd contains one entry per line for each user (or user account) of the system. All fields are separated by a colon (:) symbol. Each line contains seven attributes or fields: name, password, user ID, group ID, gecos, home directory and shell. Each attribute is separated from the adjacent attributes by colons but with no spaces. Colons must not be used in the attributes themselves, in order to avoid confusing the system. If there is no data for an attribute, there is no space, but, rather, two consecutive colons.
Generally, passwd file entry looks as follows (click to enlarge image):
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.
User ID (UID): Each user must be assigned a user ID (UID). UID 0 (zero) is reserved for root and UIDs 1-499 are reserved for other predefined accounts. Further UID 500-999 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: 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.
Tasks: To see a user list: $ cat /etc/passwd
Output: -rw-r--r-- 1 root root 2659 Sep 17 01:46 /etc/passwd
Each line in /etc/passwd represents a single user. The first listed is the root (i.e., administrative) account, which has complete power over every aspect of the system. This is followed by system-defined groups and accounts that are required for proper installation and update of system software. The lines at the end represent real people who use the system.
Understanding fields in /etc/passwd
The /etc/passwd contains one entry per line for each user (or user account) of the system. All fields are separated by a colon (:) symbol. Each line contains seven attributes or fields: name, password, user ID, group ID, gecos, home directory and shell. Each attribute is separated from the adjacent attributes by colons but with no spaces. Colons must not be used in the attributes themselves, in order to avoid confusing the system. If there is no data for an attribute, there is no space, but, rather, two consecutive colons.
Generally, passwd file entry looks as follows (click to enlarge image):
Tasks: To see a user list: $ cat /etc/passwd
Output: -rw-r--r-- 1 root root 2659 Sep 17 01:46 /etc/passwd
No comments:
Post a Comment