Differences

This shows you the differences between two versions of the page.

--- ifupdown [February 12, 2026 at 14:53] – yanevskiv
+++ ifupdown [May 14, 2026 at 11:38] (current) – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
+# ifupdown
+**ifupdown** is the traditional network manager on [[gnu-linux|GNU/Linux]] systems. It has since been replaced by [[systemd-networkd|systemd-networkd]].
+It was especially commmon in Debian systems before Debian 12 (Bookworm).
+The "if" part is short for "interface". "up" and "down" refer to `ifup` and `ifdown` commands, which are used to bring an interface link up and down + run some configuration scripts.
+## Install
+On Debian 10 and Debian 11:
+```
+sudo apt install ifupdown
+```
+Don't install ifupdown if you're using a different network manager, such as systemd-networkd!
+## Manual
+ - `man ifup`
+ - `man ifdown`
+ - `man ifquery`
+ - `man interfaces`
+## /etc/network/interfaces
+All configuration lies in `/etc/network/` directory. The following is a list of files in that directory
+```
+ $ ls /etc/network
+if-down.d  if-post-down.d  if-pre-up.d  if-up.d  interfaces  interfaces.d
+```
+The main configuration file is `/etc/network/interfaces`. The `*.d` directories contain auxiliary configuration and scripts.
+The following is the minimal possible configuration. It only configures the loopback interface. Configuring the loopback interface gives you addresses `127.0.0.1` (IPv4) and `::1` (IPv6). These are home addresses so that you can ping yourself `ping 127.0.0.1` (hence why it's called a "loopback"). Lines that begin with '#' are comments. You can comment out or change any parts of the configuration file.
+```bash
+# /etc/network/interfaces
+# Loopback
+auto lo
+iface lo inet loopback
+# ... place your other config here ...
+```
+## Configuration examples
+To configure a loopback device (the only device that's technically necessary)
+```bash
+# Loopback
+auto lo
+iface lo inet loopback
+```
+To configure an `eth0` interface dynamically (IPv4):
+```bash
+# IPv4 dynamic (DHCPv4)
+allow-hotplug eth0
+iface eth0 inet dhcp
+```
+To configure an `eth0` interface statically (IPv4):
+```bash
+# IPv4 static
+auto eth0
+iface eth0 inet static
+    address 192.168.1.50
+    netmask 255.255.255.0
+    gateway 192.168.1.1
+```
+To configure an `eth0` interface dynamically (IPv6):
+The interface acquires IPv6 through SLAAC via Router Advertisements (RA).
+No DHCPv6 required.
+```bash
+# IPv6 dynamic
+auto eth0
+iface eth0 inet6 auto
+    accept_ra
+```
+To configure an `eth0` interface statically (IPv6):
+```bash
+# IPv6 static
+auto eth0
+iface eth0 inet6 static
+    address 2001:db8:1::50
+    netmask 64
+    gateway 2001:db8:1::1
+```
+To configure an `eth0` interface statically (IPv4 + IPv6):
+```bash
+# IPv4 static block
+iface eth0 inet static
+    address 192.168.1.50
+    netmask 255.255.255.0
+    gateway 192.168.1.1
+# IPv6 static block
+iface eth0 inet6 static
+    address 2001:db8:1::50
+    netmask 64
+    gateway 2001:db8:1::1
+```
+Full configuration (loopback + IPv4 + IPv6)
+```bash
+# /etc/network/interface
+# Loopback
+auto lo
+iface lo inet loopback
+# IPv4 static block
+iface eth0 inet static
+    address 192.168.1.50
+    netmask 255.255.255.0
+    gateway 192.168.1.1
+# IPv6 static block
+iface eth0 inet6 static
+    address 2001:db8:1::50
+    netmask 64
+    gateway 2001:db8:1::1
+```
+## Commands (ifup ifdown ifquery)
+There are three commands you should know about
+ - `ifup` - Reads `/etc/network/interface` and brings an interface up
+ - `ifdown` - Reads `/etc/network/interface` and brings an interface down
+ - `ifquery` - Reads `/etc/network/interface` and tells you some information about the interface
+Bringing an `eth0` interface up:
+```
+ # ifup eth0
+```
+Bringing all interfaces up
+```
+ # ifup -a
+```
+Bringing `eth0` interface down
+```
+ # if down eth0
+```
+These examples assume your network interface is named `eth0` by [[udev|udev]].
+## Relation to ifconfig and route
+The commands `ifconfig` and `route` seem related to `ifup`, `ifdown` and `ifquery`. However the former two are rather low-level commands that modify the kernel state. The latter three are high-level commands that sit on top of the former two.
+The `ifconfig` and `route` commands are themselves considered legacy and replaced with [[ip-command|ip]] command (provided by iproute2 package) in a similar way systemd-networkd replaces ifupdown.
+## Links
+ - https://manpages.debian.org/unstable/ifupdown/
+ - https://manpages.debian.org/unstable/ifupdown/interfaces.5.en.html
+ - https://manpages.debian.org/unstable/ifupdown/ifquery.8.en.html
+ - https://manpages.debian.org/unstable/ifupdown/ifdown.8.en.html
+ - https://manpages.debian.org/unstable/ifupdown/ifup.8.en.html