D.24. /sbin/ifup

#### Linux From Scratch - Version 11.3

### Appendix D. Boot and sysconfig scripts version-20230101

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# D.24. /sbin/ifup

    #!/bin/sh
    ########################################################################
    # Begin /sbin/ifup
    #
    # Description : Interface Up
    #
    # Authors     : Nathan Coulson - nathan@linuxfromscratch.org
    #               Kevin P. Fleming - kpfleming@linuxfromscratch.org
    # Update      : Bruce Dubbs - bdubbs@linuxfromscratch.org
    #               DJ Lucas - dj@linuxfromscratch.org
    #
    # Version     : LFS 7.7
    #
    # Notes       : The IFCONFIG variable is passed to the SERVICE script
    #               in the /lib/services directory, to indicate what file the
    #               service should source to get interface specifications.
    #
    ########################################################################

    up()
    {
      log_info_msg "Bringing up the ${1} interface..."

      if ip link show $1 > /dev/null 2>&1; then
         link_status=`ip link show $1`

         if [ -n "${link_status}" ]; then
            if ! echo "${link_status}" | grep -q UP; then
               ip link set $1 up
            fi
         fi

      else
         log_failure_msg "Interface ${IFACE} doesn't exist."
         exit 1
      fi

      evaluate_retval
    }

    RELEASE="7.7"

    USAGE="Usage: $0 [ -hV ] [--help] [--version] interface"
    VERSTR="LFS ifup, version ${RELEASE}"

    while [ $# -gt 0 ]; do
       case "$1" in
          --help | -h)     help="y"; break ;;

          --version | -V)  echo "${VERSTR}"; exit 0 ;;

          -*)              echo "ifup: ${1}: invalid option" >&2
                           echo "${USAGE}" >& 2
                           exit 2 ;;

          *)               break ;;
       esac
    done

    if [ -n "$help" ]; then
       echo "${VERSTR}"
       echo "${USAGE}"
       echo
       cat << HERE_EOF
    ifup is used to bring up a network interface.  The interface
    parameter, e.g. eth0 or eth0:2, must match the trailing part of the
    interface specifications file, e.g. /etc/sysconfig/ifconfig.eth0:2.

    HERE_EOF
       exit 0
    fi

    file=/etc/sysconfig/ifconfig.${1}

    # Skip backup files
    [ "${file}" = "${file%""~""}" ] || exit 0

    . /lib/lsb/init-functions

    if [ ! -r "${file}" ]; then
       log_failure_msg "Unable to bring up ${1} interface! ${file} is missing or cannot be accessed."
       exit 1
    fi

    .  $file

    if [ "$IFACE" = "" ]; then
       log_failure_msg "Unable to bring up ${1} interface! ${file} does not define an interface [IFACE]."
       exit 1
    fi

    # Do not process this service if started by boot, and ONBOOT
    # is not set to yes
    if [ "${IN_BOOT}" = "1" -a "${ONBOOT}" != "yes" ]; then
       exit 0
    fi

    # Bring up the interface
    if [ "$VIRTINT" != "yes" ]; then
       up ${IFACE}
    fi

    for S in ${SERVICE}; do
      if [ ! -x "/lib/services/${S}" ]; then
        MSG="\nUnable to process ${file}.  Either "
        MSG="${MSG}the SERVICE '${S} was not present "
        MSG="${MSG}or cannot be executed."
        log_failure_msg "$MSG"
        exit 1
      fi
    done

    if [ "${SERVICE}" = "wpa" ]; then log_success_msg; fi

    # Create/configure the interface
    for S in ${SERVICE}; do
      IFCONFIG=${file} /lib/services/${S} ${IFACE} up
    done

    # Set link up virtual interfaces
    if [ "${VIRTINT}" == "yes" ]; then
       up ${IFACE}
    fi

    # Bring up any additional interface components
    for I in $INTERFACE_COMPONENTS; do up $I; done

    # Set MTU if requested. Check if MTU has a "good" value.
    if test -n "${MTU}"; then
       if [[ ${MTU} =~ ^[0-9]+$ ]] && [[ $MTU -ge 68 ]] ; then
          for I in $IFACE $INTERFACE_COMPONENTS; do
             ip link set dev $I mtu $MTU;
          done
       else
          log_info_msg2 "Invalid MTU $MTU"
       fi
    fi

    # Set the route default gateway if requested
    if [ -n "${GATEWAY}" ]; then
       if ip route | grep -q default; then
          log_warning_msg "Gateway already setup; skipping."
       else
          log_info_msg "Adding default gateway ${GATEWAY} to the ${IFACE} interface..."
          ip route add default via ${GATEWAY} dev ${IFACE}
          evaluate_retval
       fi
    fi

    # End /sbin/ifup

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