The "ifup" command in Linux is used to activate a network interface and bring it up. It allows you to initialize and configure a network interface, enabling network connectivity.
help
Usage: ifup <options> <ifaces...>
Options:
-h, --help this help
-V, --version copyright and version information
-a, --all process all interfaces marked "auto"
--allow CLASS ignore non-"allow-CLASS" interfaces
-i, --interfaces FILE use FILE for interface definitions
--state-dir DIR use DIR to store state information
-X, --exclude PATTERN exclude interfaces from the list of
interfaces to operate on by a PATTERN
-n, --no-act print out what would happen, but don't do it
(note that this option doesn't disable mappings)
-v, --verbose print out what would happen before doing it
-o OPTION=VALUE set OPTION to VALUE as though it were in
/etc/network/interfaces
--no-mappings don't run any mappings
--no-scripts don't run any hook scripts
--no-loopback don't act specially on the loopback device
--force force de/configuration
--ignore-errors ignore errors