220 lines
5.3 KiB
Markdown
220 lines
5.3 KiB
Markdown
# ifupdown-ng for system administrators
|
|
|
|
ifupdown-ng is a network device manager which is backwards
|
|
compatible with traditional ifup and ifdown as used on Debian
|
|
and Alpine systems, while solving many design deficits with
|
|
the original approach through robust error handling and the
|
|
use of a dependency-solver to determine interface bring-up
|
|
order.
|
|
|
|
This guide is intended to walk users through using the
|
|
ifupdown-ng system without any assumption of familiarity
|
|
with the legacy ifupdown system.
|
|
|
|
## Important Filesystem Paths
|
|
|
|
The ifupdown-ng system uses the following paths, ranked
|
|
in order of importance:
|
|
|
|
* `/etc/network/interfaces`: the interface configuration
|
|
database, which contains information about what
|
|
interfaces should be configured.
|
|
|
|
* `/run/ifstate`: the interface state file, which denotes
|
|
what physical interfaces are configured, and what
|
|
interface definition they are configured as.
|
|
|
|
* `/usr/libexec/ifupdown-ng`: this directory contains the
|
|
native ifupdown-ng executors, which are run as necessary
|
|
to configure an interface. See the ifupdown-executor(7)
|
|
manual page for more information on how these programs
|
|
are written.
|
|
|
|
* `/etc/network/if-{up|down|pre-up|post-down}.d`:
|
|
these directories contain scripts that are run when an
|
|
interface is brought up or down. In general, they follow
|
|
the same contract described in ifupdown-executor(7).
|
|
|
|
All configuration examples in this guide concern the
|
|
`/etc/network/interfaces` file.
|
|
|
|
## Basic Configuration
|
|
|
|
To begin with, lets look at a basic configuration for a
|
|
desktop computer. This scenario involves using the DHCP
|
|
helper to learn an IPv4 address dynamically.
|
|
|
|
In this case, the `/etc/network/interfaces` file would
|
|
look like:
|
|
|
|
```
|
|
auto eth0
|
|
iface eth0
|
|
use dhcp
|
|
```
|
|
|
|
These configuration statements do two things: designate
|
|
that `eth0` should be started automatically with the `auto`
|
|
keyword, and designate that the `dhcp` executor should be
|
|
used to configure the interface.
|
|
|
|
As a more detailed explanation, here is a commented version:
|
|
|
|
```
|
|
# Start eth0 automatically.
|
|
auto eth0
|
|
|
|
# Begin an interface definition for eth0.
|
|
iface eth0
|
|
|
|
# Use the dhcp executor to configure eth0.
|
|
use dhcp
|
|
```
|
|
|
|
## IPv6 RA Configuration
|
|
|
|
With IPv6, stateless auto-configuration is typically used to
|
|
configure network interfaces. If you are not interested in
|
|
using IPv4 at all, you can simply use the `ipv6-ra` executor
|
|
to ensure that an interface is configured to accept IPv6 RA
|
|
advertisements:
|
|
|
|
```
|
|
auto eth0
|
|
iface eth0
|
|
use ipv6-ra
|
|
```
|
|
|
|
## Static Configuration
|
|
|
|
We can use the `static` executor to configure static IPv4 and
|
|
IPv6 addresses. If you use the `address` keyword, the `static`
|
|
executor will automatically be used to configure the interface:
|
|
|
|
```
|
|
auto eth0
|
|
iface eth0
|
|
address 203.0.113.2/24
|
|
gateway 203.0.113.1
|
|
```
|
|
|
|
### Multiple Addresses
|
|
|
|
A typical scenario on servers is where a server has multiple
|
|
IP addresses on a single interface. In this case you simply
|
|
add additional `address` lines like this:
|
|
|
|
```
|
|
auto eth0
|
|
iface eth0
|
|
address 203.0.113.2/24
|
|
address 203.0.113.3/24
|
|
address 203.0.113.4/24
|
|
gateway 203.0.113.1
|
|
```
|
|
|
|
### Dual-stack configurations
|
|
|
|
Another typical scenario for servers is to run a dual-stack
|
|
configuration, where interfaces have both an IPv4 and an IPv6
|
|
address. This is accomplished in a similar way as multi-homing.
|
|
You specify the IPv4 and IPv6 addresses you want, followed by
|
|
gateways for each:
|
|
|
|
```
|
|
auto eth0
|
|
iface eth0
|
|
address 203.0.113.2/24
|
|
address 203.0.113.3/24
|
|
address 203.0.113.4/24
|
|
gateway 203.0.113.1
|
|
|
|
address 2001:db8:1000:2::2/64
|
|
address 2001:db8:1000:2::3/64
|
|
address 2001:db8:1000:2::4/64
|
|
gateway 2001:db8:1000:2::1
|
|
```
|
|
|
|
## Relationships
|
|
|
|
As previously mentioned, ifupdown-ng features a dependency
|
|
resolver that allows for determining the interface configuration
|
|
order.
|
|
|
|
|
|
|
|
In order to make use of this, dependencies can be managed in one
|
|
of two ways:
|
|
|
|
### Explicit dependency management using `requires`
|
|
|
|
The `requires` keyword can be used to manage explicit
|
|
dependencies:
|
|
|
|
```
|
|
auto eth0
|
|
iface eth0
|
|
use dhcp
|
|
|
|
auto gre0
|
|
iface gre0
|
|
requires eth0
|
|
|
|
use gre
|
|
gre-endpoint 203.0.113.2
|
|
gre-ttl 255
|
|
gre-flags ignore-df
|
|
|
|
address 203.0.113.194/30
|
|
gateway 203.0.113.193
|
|
```
|
|
|
|
### Implicit dependency management using executors
|
|
|
|
Executors can declare implicit dependencies which work the same
|
|
way as explicit dependencies, but are learned at run-time, for
|
|
example:
|
|
|
|
```
|
|
auto bond0
|
|
iface bond0
|
|
use bond
|
|
|
|
bond-members eth0 eth1
|
|
[...]
|
|
```
|
|
|
|
Is equivalent to:
|
|
|
|
```
|
|
auto bond0
|
|
iface bond0
|
|
use bond
|
|
|
|
requires eth0 eth1
|
|
[...]
|
|
```
|
|
|
|
## Executors
|
|
|
|
The ifupdown-ng system is expanded with additional features via
|
|
executors. Executors are selected on a per-interface basis using
|
|
`use` statements, for example:
|
|
|
|
```
|
|
auto eth0
|
|
iface eth0
|
|
use dhcp
|
|
```
|
|
|
|
Executors are run in the order specified by the `use` statements.
|
|
Some executors are automatically added based on other statements
|
|
in an interface definition. To see the full list of executors
|
|
used for an interface, use the ifquery(8) command.
|
|
|
|
## Questions
|
|
|
|
If you have further questions about how to use ifupdown-ng to
|
|
configure a specific scenario, drop by the [ifupdown-ng IRC channel][irc].
|
|
|
|
[irc]: irc://irc.as7007.net/#ifupdown-ng
|