The ifconfig command has been deprecated and thus missing by default on Debian Linux, starting from Debian stretch.
# ifconfig
-bash: ifconfig: command not found
The new and recommended alternative for examining a network configuration on Debian Linux is ip command. For example to use ip command to display a network configuration run the following:
# ip address
The above ip command can be abbreviated to:
# ip a
If you still prefer to use ifconfig as part of your daily sys admin routine, you can easily install it as part of the net-tools package.
Requirements
Privileged access to your Debian Linux system is required.
Difficulty
EASY
Conventions
# - requires given linux commands to be executed with root privileges either directly as a root user or by use of sudo command
$ - requires given linux commands to be executed as a regular non-privileged user