doc: Add Building instructions for Ubuntu 18.04

Signed-off-by: Martin Winter <mwinter@opensourcerouting.org>

doc/developer/building-frr-on-ubuntu1804.rst

@@ -0,0 +1,171 @@
+Ubuntu 18.04LTS
+===============================================
+
+Install required packages
+-------------------------
+
+Add packages:
+
+::
+
+    apt-get install git autoconf automake libtool make gawk libreadline-dev \
+       texinfo pkg-config libpam0g-dev libjson-c-dev bison flex \
+       python-pytest libc-ares-dev python3-dev libsystemd-dev python-ipaddr \
+       python3-sphinx
+
+Get FRR, compile it and install it (from Git)
+---------------------------------------------
+
+**This assumes you want to build and install FRR from source and not
+using any packages**
+
+Add frr groups and user
+~~~~~~~~~~~~~~~~~~~~~~~
+
+::
+
+    sudo groupadd -g 92 frr
+    sudo groupadd -r -g 85 frrvty
+    sudo adduser --system --ingroup frr --home /var/run/frr/ \
+       --gecos "FRR suite" --shell /sbin/nologin frr
+    sudo usermod -a -G frrvty frr
+
+Download Source, configure and compile it
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+(You may prefer different options on configure statement. These are just
+an example.)
+
+::
+
+    git clone https://github.com/frrouting/frr.git frr
+    cd frr
+    ./bootstrap.sh
+    ./configure \
+        --prefix=/usr \
+        --enable-exampledir=/usr/share/doc/frr/examples/ \
+        --localstatedir=/var/run/frr \
+        --sbindir=/usr/lib/frr \
+        --sysconfdir=/etc/frr \
+        --enable-pimd \
+        --enable-watchfrr \
+        --enable-ospfclient=yes \
+        --enable-ospfapi=yes \
+        --enable-multipath=64 \
+        --enable-user=frr \
+        --enable-group=frr \
+        --enable-vty-group=frrvty \
+        --enable-configfile-mask=0640 \
+        --enable-logfile-mask=0640 \
+        --enable-rtadv \
+        --enable-fpm \
+        --enable-systemd=yes \
+        --with-pkg-git-version \
+        --with-pkg-extra-version=-MyOwnFRRVersion
+    make
+    make check
+    sudo make install
+
+Create empty FRR configuration files
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+::
+
+    sudo install -m 755 -o frr -g frr -d /var/log/frr
+    sudo install -m 775 -o frr -g frrvty -d /etc/frr
+    sudo install -m 640 -o frr -g frr /dev/null /etc/frr/zebra.conf
+    sudo install -m 640 -o frr -g frr /dev/null /etc/frr/bgpd.conf
+    sudo install -m 640 -o frr -g frr /dev/null /etc/frr/ospfd.conf
+    sudo install -m 640 -o frr -g frr /dev/null /etc/frr/ospf6d.conf
+    sudo install -m 640 -o frr -g frr /dev/null /etc/frr/isisd.conf
+    sudo install -m 640 -o frr -g frr /dev/null /etc/frr/ripd.conf
+    sudo install -m 640 -o frr -g frr /dev/null /etc/frr/ripngd.conf
+    sudo install -m 640 -o frr -g frr /dev/null /etc/frr/pimd.conf
+    sudo install -m 640 -o frr -g frr /dev/null /etc/frr/ldpd.conf
+    sudo install -m 640 -o frr -g frr /dev/null /etc/frr/nhrpd.conf
+    sudo install -m 640 -o frr -g frrvty /dev/null /etc/frr/vtysh.conf
+
+Enable IPv4 & IPv6 forwarding
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Edit ``/etc/sysctl.conf`` and uncomment the following values (ignore the
+other settings)
+
+::
+
+    # Uncomment the next line to enable packet forwarding for IPv4
+    net.ipv4.ip_forward=1
+
+    # Uncomment the next line to enable packet forwarding for IPv6
+    #  Enabling this option disables Stateless Address Autoconfiguration
+    #  based on Router Advertisements for this host
+    net.ipv6.conf.all.forwarding=1
+
+Enable MPLS Forwarding (with Linux Kernel >= 4.5)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Edit ``/etc/sysctl.conf`` and the following lines. Make sure to add a
+line equal to ``net.mpls.conf.eth0.input`` or each interface used with
+MPLS
+
+::
+
+    # Enable MPLS Label processing on all interfaces
+    net.mpls.conf.eth0.input=1
+    net.mpls.conf.eth1.input=1
+    net.mpls.conf.eth2.input=1
+    net.mpls.platform_labels=100000
+
+Add MPLS kernel modules
+~~~~~~~~~~~~~~~~~~~~~~~
+
+Add the following lines to ``/etc/modules-load.d/modules.conf``:
+
+::
+
+    # Load MPLS Kernel Modules
+    mpls-router
+    mpls-iptunnel
+
+**Reboot** or use ``sysctl -p`` to apply the same config to the running
+system
+
+Install the systemd service (if rebooted from last step, change directory back to frr directory)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+::
+
+    sudo install -m 644 tools/frr.service /etc/systemd/system/frr.service
+    sudo install -m 644 tools/etc/default/frr /etc/default/frr
+    sudo install -m 644 tools/etc/frr/daemons /etc/frr/daemons
+    sudo install -m 644 tools/etc/frr/daemons.conf /etc/frr/daemons.conf
+    sudo install -m 644 tools/etc/frr/frr.conf /etc/frr/frr.conf
+    sudo install -m 644 -o frr -g frr tools/etc/frr/vtysh.conf /etc/frr/vtysh.conf
+
+Enable daemons
+~~~~~~~~~~~~~~
+
+| Edit ``/etc/frr/daemons`` and change the value from "no" to "yes" for
+  those daemons you want to start by systemd.
+| For example.
+
+::
+
+    zebra=yes
+    bgpd=yes
+    ospfd=yes
+    ospf6d=yes
+    ripd=yes
+    ripngd=yes
+    isisd=yes
+
+Enable the systemd service
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+-  systemctl enable frr
+
+Start the systemd service
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+-  systemctl start frr
+-  use ``systemctl status frr`` to check its status.