add blog article on how to use sexy to boostrap a network
Signed-off-by: Nico Schottelius <nico@brief.schottelius.org>
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blog/sexy-network-bootstrap.mdwn
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blog/sexy-network-bootstrap.mdwn
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[[!meta title="Bootstrapping a network with sexy"]]
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## Introduction
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This article will explain how to begin to manage a network
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with [[sexy|software/sexy]]. I assume you can start almost on a green field,
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if not, insert your site specific changes into the process.
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## Prerequisites
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First of all, you need to have sexy installed, as described on
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the [[sexy homepage|software/sexy]]. Secondly, if you already played
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around with sexy, you should empty the sexy database, which is located
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at **~/.sexy**:
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% rm -rf ~/.sexy
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Or, if you are using **git** to manage your ~/.sexy directory, create a fresh
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branch, which does not contain any files:
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% cd ~/.sexy
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% git checkout -b network_bootstrap
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# Ensure all (committed and non-committed) files are gone
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% rm -rf db/ backend/
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% git rm -r db/ backend/
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% git commit -m "Empty sexy database"
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## Add the first host
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First of all, let us add a host. Sexy wants to know its type (virtual machine
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or hardware). Sexy expects all names as fully qualified domain names (FQDNs):
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% sexy host add -t hw katze.intern.schottelius.org
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**Hint:** You can use the **-h** flag to get help for any command.
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Using **host list**, we can verify the host has been added:
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% sexy host list
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katze.intern.schottelius.org
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Now we can network cards to this host:
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% sexy host nic-add -m 00:00:24:c8:da:bc -n eth0 katze.intern.schottelius.org
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% sexy host nic-add -m 00:00:24:c8:da:bd -n eth1 katze.intern.schottelius.org
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## Add the network
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In sexy, the host and net-ipv4 areas are disconnected: You can use sexy to manage
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only hosts, to manage only networks or to manage both. To allow this flexibility,
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the network part does not know about any information from the host part.
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Luckily enough, you don't need to re-enter the information, but you can retrieve
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them from the database. Currently, sexy only allows you to manage IPv4 based networks
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- IPv6 may be added in future releases. So the command to remember for now, is
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**net-ipv4**:
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% sexy net-ipv4 add --mask 22 192.168.24.0
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% sexy net-ipv4 list
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192.168.24.0
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Now we created the network 192.168.24.0/22.
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## Add a host to a network
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The previously added host, **katze.intern.schottelius.org**, is the router of
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my home network and it should use the first IPv4 address in the network.
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The **net-ipv4 host-add** command can be used to add a host:
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% sexy net-ipv4 host-add
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usage: sexy net-ipv4 host-add [-h] [-d] [-v] -m MAC_ADDRESS -f FQDN
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[-i IPV4_ADDRESS]
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network
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So adding the host to a network requires giving in at least the mac address,
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which we entered before. So we can use the following line to add the host to
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our new network:
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% host=katze.intern.schottelius.org
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% mac=$(sexy host nic-addr-get -n eth0 $host)
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% sexy net-ipv4 host-add -m $mac -f $host 192.168.24.0
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Sexy will be default use the next free address and as this is the first host in
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the network, it used .1:
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% sexy net-ipv4 host-ipv4-address-get 192.168.24.0 -f katze.intern.schottelius.org
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192.168.24.1
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## Making use of the entered information
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Sexy does not know which DNS or DHCP server you may be using.
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To implement changes to your architecture (probably using
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a software like [[cdist|software/cdist]]), sexy supports using
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**backends**.
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For my home network, I am going to use
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[dnsmasq](http://www.thekelleys.org.uk/dnsmasq/doc.html), because the
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router is a small [Soekris net5501](http://soekris.com/net5501.htm).
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The backends are stored in **~/.sexy/backend** and for this
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example tutorial, I will only create **~/.sexy/backend/net-ipv4/apply**:
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% cat ~/.sexy/backend/net-ipv4/apply
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#!/bin/sh -e
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cdist_base="/home/users/nico/p/cdist/nico"
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cdist_bin="$cdist_base/bin/cdist"
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dst_dir="$cdist_base/conf/type/__nico_router/files/dnsmasq.d"
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tmp=$(mktemp /tmp/foooooo.XXXXXXXXXXXXXXXX)
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for network in "$@"; do
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dstfile="${dst_dir}/${network}-dhcp.conf"
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cat << eof > "$tmp"
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# WARNING: sexy generated file, do *not* edit directly.
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eof
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for fqdn in $(sexy net-ipv4 host-list $network); do
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mac=$(sexy net-ipv4 host-mac-address-get -f "$fqdn" "$network")
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ipv4a=$(sexy net-ipv4 host-ipv4-address-get -f "$fqdn" "$network")
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hostname=$(echo $fqdn | sed 's/\..*//')
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line="dhcp-host=${mac},$ipv4a,$hostname"
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echo "${line}" >> "${tmp}"
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done
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mv "${tmp}" "${dstfile}"
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eof
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done
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cd "${dst_dir}"
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git add .
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git commit -m "Update Sexy generated network configuration" -o -- .
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echo "Transferring changes to git remote"
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git pull
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git push
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"$cdist_bin" config -v zuhause.schottelius.org
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This backend in essence creates the dnsmasq configuration and executes cdist afterwards
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to apply the changes.
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## Adding more hosts
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To make this tutorial useful and my router actually provide a dhcp
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server, I'll add my notebook and the fileserver to sexy:
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% sexy host add -t hw loch.intern.schottelius.org
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% sexy host nic-add -m f4:6d:04:71:c5:ce loch.intern.schottelius.org
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% sexy net-ipv4 host-add -m $(sexy host nic-addr-get -n nic0 loch.intern.schottelius.org) -f loch.intern.schottelius.org 192.168.24.0
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% sexy host add -t hw brief.intern.schottelius.org
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% sexy host nic-add -m b8:8d:12:15:fd:fa brief.intern.schottelius.org
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% sexy net-ipv4 host-add -m $(sexy host nic-addr-get -n nic0 brief.intern.schottelius.org) -f brief.intern.schottelius.org 192.168.24.0
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As you can see, if I do not specify the name of the nic, sexy automatically uses **nic0**
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for the first nic and counts up. This decision was made, as network device names vary between
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operating systems and even operating system versions.
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## The result
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Using only the steps above, I've created a sexy maintained network,
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**192.168.24.0/22**, which calls [[cdist|software/cdist]] to configure
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the router with dnsmasq.
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You can browse
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[the real sexy database](http://git.schottelius.org/?p=sexy-database;a=summary)
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created during this tutorial, as well as
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the [cdist configuration](http://git.schottelius.org/?p=cdist-nico;a=summary)
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that is used to configure the router.
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[[!tag localch net sexy unix]]
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