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getent command in Linux with examples

Last Updated : 03 Sep, 2024

The 'getent' command in Linux is a powerful tool that allows users to access entries from various important text files or databases managed by the Name Service Switch (NSS) library. This command is widely used for retrieving user and group information, among other data, stored in databases such as 'passwd', 'group', 'hosts', and more. 'getent' provides a consistent and unified way to query the local files like '/etc/passwd' or network information sources such as LDAP.

The 'getent' (short for "get entries") command fetches entries from specified databases supported by NSS. This makes it a versatile tool for looking up a wide range of information on a Linux system, including user accounts, groups, hosts, services, and more. Since it uses the same name service as the system, 'getent' can retrieve data from both local files and network sources like LDAP, providing a complete view of the requested information.

The 'getent' command can query several databases, each serving a different purpose. Some of the most commonly accessed databases include:

• 'passwd': Retrieves user account information.
• 'group': Fetches group account details.
• 'hosts': Looks up hostnames and IP addresses.
• 'services': Displays network services and their associated ports.
• 'protocols': Lists network protocols.
• 'networks': Retrieves network names.
• 'shadow': Shows user password information (requires proper permissions).
• 'aliases': Provides mail alias information.

Other databases 'getent' can query include 'ahosts', 'ahostsv4', 'ahostsv6' (for address resolution), 'ethers' (Ethernet addresses), 'gshadow' (secure group information), 'netgroup', 'rpc' (remote procedure call), and more.

Here are some practical examples:

Fetch the list of user accounts on a Linux system (stored in a database known as 'passwd'). This will show all the user accounts, regardless of the type of name service being used. For example, if both the local and the LDAP name service are used for user accounts, the results will include all the local and the LDAP users:

Syntax:

getent database [key ...]

Output:

Explanation: This command displays all user accounts, including those from both local and network sources like LDAP.

If we want to fetch details for a particular user called 'rahul' then,

Syntax:

getent passwd rahul

Output:

Explanation: This outputs the user details from the 'passwd' database, including the username, user ID, group ID, home directory, and default shell.

If we want to fetch a list of group accounts on a Unix system (stored in a database called 'group') then,

Syntax:

getent group

Output:

Explanation: This shows details of each group, including group name, group ID, and group members.

While 'getent' is simple in its basic usage, it also offers options to modify its behavior:

• '-s service, --service service': This option overrides all the databases with the specified service.(Since glibc 2.2.5.)
• '-s database:service, --service database:service': This option override only the specified databases with the specified service. The option may be used for multiple times, but only the last service for each of the database will be used.(Since glibc 2.4.)
• '-i, --no-idn': This option disables IDN encoding in the lookups for ahosts/getaddrinfo(3) (Since glibc-2.13.)
• '-?, --help': This option prints a usage summary and exit.
• '--usage': This option prints a short usage summary and exit.
• '-V, --version': This option prints the version number, license, and the disclaimer of warranty for 'getent'.

One of the following exit values can be used to returned by getent:

• 0: This exit status shows that the Command completed successfully.
• 1: This exit status shows that there's a Missing arguments, or database unknown.
• 2: This exit status shows that One or more supplied key could not be found in the database.
• 3: This exit status shows that the Enumeration not supported on this database.

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