ifdown Command in Linux

Introduction

Linux ifdown command is a basic Linux command used to deactivate a network interface. It's often grouped with ifup and ifquery due to the similarities.

The following text elaborates on Linux ifdown command.

Prerequisites

• Linux system (this tutorial uses Ubuntu 22.04).
• Access to the terminal.
• ifdown command installed.
• sudo permissions.

ifdown Command Syntax

The ifdown command syntax is:

ifdown [options] [interface]

Running ifdown without any options or interface doesn't produce output. The [interface] components are mandatory. However, options serve to customize the command but are not necessary.

ifdown Command Options

The ifdown command has several arguments which change its output. The following table lists ifdown options:

Option	Description
-a, --all	Deactivates all interfaces.
--allow CLASS	Ignores non-"allow-CLASS" interfaces in /etc/network/interfaces.
-i, --interfaces FILE	Uses FILE for interface definitions instead of /etc/network/interfaces.
--state-dir DIR	Uses DIR to store state information.
-X, --exclude PATTERN	Excludes interfaces from the list of interfaces to operate on by the PATTERN.
-n, --no-act	Simulates the command without actually executing it.
-v, --verbose	Shows what would happen before executing.
-o OPTION=VALUE	Sets OPTION to VALUE as though it were in /etc/network/interfaces.
--no-mappings	Doesn't run any mappings.
--no-scripts	Doesn't run hook scripts.
-nv	Prints non-verbose output.
--no-loopback	Prompts the command not to perform any deactivation on the loopback device.
--force	Forces the command to run even if the interface is not configured.
--ignore-errors	Signals the command to ignore errors.
-h, --help	Prints the help message.
-V, --version	Prints copyright and version information.

ifdown Command Examples

Due to the variety of arguments, ifdown has multiple practical examples. However, before running ifdown, a user must know the interface names. Use the ip or deprecated ifconfig command to check interface names.

For instance, to verify the interface names with ip, run:

ip link show

On the other hand, use the following command to accomplish the same:

ifconfig -a

Both commands show currently active network interfaces.

The following sections present some ifdown use cases.

Bring Down Active Interfaces

Do deactivate all interfaces, run:

sudo ifdown -a

The command has no output.

Print Verbose Output

To display additional info in the command output, run the command with -v:

sudo ifdown -av

To verify all interfaces are down, use the ping command. For instance, ping Google with:

ping google.com

The command prints no output.

Disable a Specific Interface

To bring down a specific interface, use the syntax:

sudo ifdown -v [interface][configuration]

This command provides a verbose output. For instance, turn off the specific configuration of the interface lo with:

sudo ifdown -v lo=lo

Use ifconfig or ip link show to confirm the interface is not listed.

Simulate Interface Deactivation

Simulating network interface deactivation without altering system configurations is beneficial for testing and development. The procedure allows users to test the deactivation impact before implementing changes to the network, ensuring a controlled and predictable environment. This is especially useful when scripting or automating network interface management processes.

To simulate the command without executing it, run:

ifdown --no-act [configuration][interface]

For instance, to simulate ifdown on the lo interface without executing the command, run:

ifdown --no-act lo=lo

Conclusion

After reading this article, you know everything about the Linux ifdown command. Additionally, the guide provided the most common use cases.

To learn about other Linux commands, refer to our Linux commands cheat sheet.