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# Move the client device into the container's net namespace
sudo ip link set $client netns $ns
Then we configure the host side:
sudo ip link set $host up
sudo ip addr add 10.0.0.1/24 dev $host
@dots{}and then we configure the client side:
sudo ip netns exec $ns ip link set lo up
sudo ip netns exec $ns ip link set $client up
sudo ip netns exec $ns ip addr add 10.0.0.2/24 dev $client
At this point the host can reach the container at IP address 10.0.0.2, and the container can reach the host at IP 10.0.0.1. This is all we need to talk to the database server inside the container from the host system on the outside.
$ psql -h 10.0.0.2 -U test
psql (14.4)
Type "help" for help.
test=> CREATE TABLE hello (who TEXT NOT NULL);
CREATE TABLE
test=> INSERT INTO hello (who) VALUES ('world');
INSERT 0 1
test=> SELECT * FROM hello;
who
-------
world
(1 row)
Now that we're done with this little demonstration let's clean up:
sudo kill $pid
sudo ip netns del $ns
sudo ip link del $host
Guix can produce disk images (@pxref{Invoking guix system,,, guix, GNU Guix Reference Manual}) that can be used with virtual machines solutions such as virt-manager, GNOME Boxes or the more bare QEMU, among others.
This chapter aims to provide hands-on, practical examples that relates to the usage and configuration of virtual machines on a Guix System.
Network bridge interface
networking, bridge
qemu, network bridge
By default, QEMU uses a so-called ``user mode'' host network back-end, which is convenient as it does not require any configuration. Unfortunately, it is also quite limited. In this mode, the guest @abbr{VM, virtual machine} can access the network the same way the host would, but it cannot be reached from the host. Additionally, since the QEMU user networking mode relies on ICMP, ICMP-based networking tools such as @command{ping} do @emph{not} work in this mode. Thus, it is often desirable to configure a network bridge, which enables the guest to fully participate in the network. This is necessary, for example, when the guest is to be used as a server.
Creating a network bridge interface
There are many ways to create a network bridge. The following command shows how to use NetworkManager and its @command{nmcli} command line interface (CLI) tool, which should already be available if your operating system declaration is based on one of the desktop templates:
# nmcli con add type bridge con-name br0 ifname br0
To have this bridge be part of your network, you must associate your network bridge with the Ethernet interface used to connect with the network. Assuming your interface is named @samp{enp2s0}, the following command can be used to do so:
# nmcli con add type bridge-slave ifname enp2s0 master br0
Important
Only Ethernet interfaces can be added to a bridge. For wireless interfaces, consider the routed network approach detailed in @xref{Routed network for libvirt}.
By default, the network bridge will allow your guests to obtain their IP address via DHCP, if available on your local network. For simplicity, this is what we will use here. To easily find the guests, they can be configured to advertise their host names via mDNS.
Configuring the QEMU bridge helper script
QEMU comes with a helper program to conveniently make use of a network bridge interface as an unprivileged user @pxref{Network options,,, QEMU, QEMU Documentation}. The binary must be made setuid root for proper operation; this can be achieved by adding it to the @code{setuid-programs} field of your (host) @code{operating-system} definition, as shown below:
(setuid-programs
(cons (file-append qemu "/libexec/qemu-bridge-helper")
%setuid-programs))
The file @file{/etc/qemu/bridge.conf} must also be made to allow the bridge interface, as the default is to deny all. Add the following to your list of services to do so:
(extra-special-file "/etc/qemu/host.conf" "allow br0\n")
Invoking QEMU with the right command line options
When invoking QEMU, the following options should be provided so that the network bridge is used, after having selected a unique MAC address for the guest.

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  1. guix
  2. documentation-cookbook
  3. English
By default, QEMU uses a so-called ``user mode'' host network back-end, which is convenient as it does not require any configuration. Unfortunately, it is also quite limited. In this mode, the guest @abbr{VM, virtual machine} can access the network the same way the host would, but it cannot be reached from the host. Additionally, since the QEMU user networking mode relies on ICMP, ICMP-based networking tools such as @command{ping} do @emph{not} work in this mode. Thus, it is often desirable to configure a network bridge, which enables the guest to fully participate in the network. This is necessary, for example, when the guest is to be used as a server.
By default, QEMU uses a so-called ``user mode'' host network back-end, which is convenient as it does not require any configuration. Unfortunately, it is also quite limited. In this mode, the guest @abbr{VM, virtual machine} can access the network the same way the host would, but it cannot be reached from the host. Additionally, since the QEMU user networking mode relies on ICMP, ICMP-based networking tools such as @command{ping} do @emph{not} work in this mode. Thus, it is often desirable to configure a network bridge, which enables the guest to fully participate in the network. This is necessary, for example, when the guest is to be used as a server.
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type: Plain text
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Source string location
guix-git/doc/guix-cookbook.texi:3743
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4 months ago
Last updated
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po/doc/guix-cookbook.pot, string 805