netctl

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netctl is a CLI-based tool used to configure and manage network connections via profiles.

Installation

netctl is part of the base group, so it should already be installed on your system. Otherwise install it as usual.

Optional dependencies are shown in the table below.

Feature Dependency netctl program
(if relevant)
Automatic wireless connections wpa_actiond netctl-auto
Automatic wired connections ifplugd netctl-ifplugd
WPA wpa_supplicant
DHCP dhcpcd or dhclient
Wifi menus dialog
PPPoE ppp
Warning: Do not enable concurrent, conflicting network services. Use systemctl --type=service to ensure that no other network service is running before enabling a netctl profile/service.

Usage

It is advisable to read the following man pages before using netctl:

Configuration

netctl uses profiles to manage network connections and different modes of operation to start profiles automatically or manually on demand.

Profile configuration

The netctl profile files are stored in /etc/netctl/ and example configuration files are available in /etc/netctl/examples/. Common configurations include:

  • ethernet-dhcp
  • ethernet-static
  • wireless-wpa
  • wireless-wpa-static

To use an example profile, simply copy it from /etc/netctl/examples/ to /etc/netctl/ and configure it to your needs; see basic #Example profiles below. The first parameter you need to create a profile is the network Interface, see Network configuration#Device names for details.

Tip:
  • For wireless settings, you can use wifi-menu -o as root to generate the profile file in /etc/netctl/.
  • To enable a static IP profile on wired interface no matter if the cable is connected or not, use SkipNoCarrier=yes in your profile.

Once you have created your profile, attempt to establish a connection (use only the profile name, not the full path):

# netctl start profile

If the above command results in a failure, then use journalctl -xn and netctl status profile to obtain a more in depth explanation of the failure.

Automatic operation

If you use only one profile (per interface) or want to switch profiles manually, the Basic method will do. Most common examples are servers, workstations, routers etc.

If you need to switch multiple profiles frequently, use Automatic switching of profiles. Most common examples are laptops.

Basic method

With this method, you can statically start only one profile per interface. First manually check that the profile can be started successfully with:

# netctl start profile 

then it can be enabled using:

# netctl enable profile

This will create and enable a systemd service that will start when the computer boots. Changes to the profile file will not propagate to the service file automatically. After such changes, it is necessary to reenable the profile:

# netctl reenable profile

After enabling a profile, it will be started at next boot. Obviously this can only be successful, if the network cable for a wired connection is plugged in, or the wireless access point used in a profile is in range respectively.

Automatic switching of profiles

netctl provides special systemd services for automatically switching of profile for wired and wireless connections:

  • For wired interfaces, install package ifplugd: After starting and enabling netctl-ifplugd@interface.service DHCP profiles are started/stopped when the network cable is plugged in/unplugged.
    • The netctl-ifplugd@interface.service will prefer profiles which use DHCP.
    • To automatically start a static IP profile the option ExcludeAuto=no needs to be set in it.
    • To prioritize a profile with a static IP over DHCP profiles, you can set Priority=2, which is higher than the default priority given to DHCP profiles of Priority=1.
  • For wireless interfaces, install package wpa_actiond: After starting and enabling netctl-auto@interface.service profiles are started/stopped automatically as you move from the range of one network into the range of another network (roaming).
    • Profiles must use Security=wpa-configsection or Security=wpa to work with netctl-auto rather than Security=wpa-config.
    • If you want some wireless profile not to be started automatically by netctl-auto@interface.service, you have to explicitly add ExcludeAuto=yes to that profile.
    • You can use priority= in the WPAConfigSection (see /etc/netctl/examples/wireless-wpa-configsection) to set priority of a profile when multiple wireless access points are available.

Note that interface is not literal, but to be substituted by the name of your device's interface, e.g. netctl-auto@wlp4s0.service. See netctl.profile(5) for details.

Warning:
  • If any of the profiles contain errors, such as an empty or misquoted Key= variable, the unit will fail to load with the message "Failed to read or parse configuration '/run/network/wpa_supplicant_wlan0.conf', even when that profile is not being used.
  • This method conflicts with the Basic method. If you have previously enabled a profile through netctl, run netctl disable profile to prevent the profile from starting twice at boot.

Since netctl 1.3 it is possible to manually control an interface otherwise managed by netctl-auto without having to stop netctl-auto.service. This is done using the netctl-auto command. For a list of available actions run:

 # netctl-auto --help

Example profiles

Wired

For a DHCP connection, only the Interface has to be configured after copying the /etc/netctl/examples/ethernet-dhcp example profile to /etc/netctl.

For example:

/etc/netctl/my_dhcp_profile
Interface=enp1s0
Connection=ethernet
IP=dhcp

For a static IP configuration copy the /etc/netctl/examples/ethernet-static example profile to /etc/netctl and modify Interface, Address, Gateway and DNS) as needed.

For example:

/etc/netctl/my_static_profile
Interface=enp1s0
Connection=ethernet
IP=static
Address=('10.1.10.2/24')
Gateway=('10.1.10.1')
DNS=('10.1.10.1')

Take care to include the subnet notation of /24. It equates to a netmask of 255.255.255.0) and without it the profile will fail to start. See also CIDR notation. To alias more than one IP address per a NIC set Address=('10.1.10.2/24' '192.168.1.2/24').

Wireless (WPA-PSK)

Tango-edit-clear.pngThis article or section needs language, wiki syntax or style improvements.Tango-edit-clear.png

Reason: Split into multiple sections, keep here only the example at the bottom. wifi-menu related to WPA-PSK in any way. (Discuss in Talk:Netctl#)

The following applies for the standard wireless connections using a pre-shared key (WPA-PSK). See WPA2 Enterprise#netctl for example profiles with other authentication methods.

The standard netctl tool to connect to a wireless network (WPA-PSK, WEP) interactively is wifi-menu; used with the -o option:

wifi-menu -o 

it generates the configuration file in /etc/netctl/ for the network to use for #Automatic operation at the same time.

Alternatively, the profile may also be configured manually, as follows:

Copy the example file wireless-wpa from /etc/netctl/examples to /etc/netctl (name of your choice):

# cp /etc/netctl/examples/wireless-wpa /etc/netctl/.

Edit the profile as needed (modifying Interface, ESSID and Key) and it is done.

At this step you may want to re-confirm the new profile you created is chmod 600 and confirm it works by starting it:

netctl start wireless-wpa

before configuring any #Automatic operation.

Optionally you can also follow the following step to obfuscate the wireless passphrase (wifi-menu does it automatically):

Users not wishing to have the passphrase to their wireless network stored in plain text have the option of storing the corresponding 256-bit pre-shared key instead, which is calculated from the passphrase and the SSID using standard algorithms.

Calculate your 256-bit PSK using wpa_passphrase:

$ wpa_passphrase your_essid
network={
  ssid="your_essid"
  #psk="passphrase"
  psk=64cf3ced850ecef39197bb7b7b301fc39437a6aa6c6a599d0534b16af578e04a
}

The pre-shared key (psk) now needs to replace the plain text passphrase of the Key variable in the profile. Once completed your network profile wireless-wpa containing a 256-bit PSK should resemble:

/etc/netctl/wireless-wpa
Description='A simple WPA encrypted wireless connection using 256-bit PSK'
Interface=wlp2s2
Connection=wireless
Security=wpa
IP=dhcp
ESSID=your_essid
Key=\"64cf3ced850ecef39197bb7b7b301fc39437a6aa6c6a599d0534b16af578e04a
Note:
  • Make sure to use the special quoting rules for the Key variable as explained at the end of netctl.profile(5).
  • If the passphrase fails, try removing the \" in the Key variable.
  • Although "encrypted", the key that you put in the profile configuration is enough to connect to a WPA-PSK network. Therefore this process is only useful for hiding the human-readable version of the passphrase. This will not prevent anyone with read access to this file from connecting to the network.

Tips and tricks

Using an Experimental GUI

If you want a graphical user interface to manage netctl and your connections and you are not afraid of highly experimental unofficial packages, there are some options available. netctl-guiAUR provides a Qt-based graphical interface, DBus daemon and KDE widget. An alternative is netmenuAUR, which uses dmenu as its graphical interface.

Eduroam

See WPA2 Enterprise#netctl.

Bonding

From kernel documentation:

The Linux bonding driver provides a method for aggregating multiple network interfaces into a single logical "bonded" interface. The behavior of the bonded interfaces depends on the mode. Generally speaking, modes provide either hot standby or load balancing services. Additionally, link integrity monitoring may be performed.

Load balancing

To use bonding with netctl, additional package from official repositories is required: ifenslave.

Copy /etc/netctl/examples/bonding to /etc/netctl/bond0 and edit it, for example:

/etc/netctl/bond0
Description='Bond Interface'
Interface='bond0'
Connection=bond
BindsToInterfaces=('eth0' 'eth1')
IP=dhcp
IP6=stateless

Now you can disable your old configuration and set bond0 to be started automatically. Switch to the new profile, for example:

# netctl switch-to bond0
Note: This uses the round-robin policy, which is the default for the bonding driver. See official documentation for details.
Tip: To check the status and bonding mode:
$ cat /proc/net/bonding/bond0

Wired to wireless failover

This example describes how to use bonding to fallback to wireless when the wired ethernet goes down. This is most useful when both the wired and wireless interface will be connected to the same network. Your wireless router/access point must be configured in bridge mode.

You will need additional packages from the official repositories: ifenslave and wpa_supplicant.

First enable the bonding module to be loaded upon boot time, as instructed on Kernel modules#Automatic module handling:

/etc/modules-load.d/bonding.conf
bonding

Then, configure the options of the bonding driver to use active-backup and configure the primary parameter to the device you want to be the active one (normally the wired interface). Also, be sure to use the same device name as returned when running ip link:

/etc/modprobe.d/bonding.conf
options bonding mode=active-backup miimon=100 primary=eth0 max_bonds=0

The miimon option is needed, for the link failure detection. The max_bonds option avoids the Interface bond0 already exists error. More information can be obtained on the kernel documentation.

Next, configure a netctl profile to enslave the two hardware interfaces. Use the name of all the devices you want to enslave. If you have more than two wired or wireless interfaces, you can enslave all of them on a bond interface. But, for most cases you will have only two devices, a wired and a wireless one:

/etc/netctl/failover
Description='A wired connection with failover to wireless'
Interface='bond0'
Connection=bond
BindsToInterfaces=('eth0' 'wlan0')
IP='dhcp'

Disable any other profiles (specially a wired or wireless) you had enabled before and then enable the failover profile on startup:

# netctl enable failover

Now you need to configure wpa_supplicant to connect to any known network you wish. You should create a file for each interface and enable it on systemd. Create the following file with this content:

/etc/wpa_supplicant/wpa_supplicant-wlan0.conf
ctrl_interface=/run/wpa_supplicant
update_config=1

And append to the end of this file any network you want to connect to:

network={
    ssid="SSID"
    psk=PSK
}

To generate the obfuscated PSK you can run wpa_passphrase as on the WPA supplicant#Connecting with wpa_passphrase page.

Now, enable the wpa_supplicant@ template service on the network interface, for example wpa_supplicant@wlan0.

You can try now to reboot your machine and see if your configuration worked.

Note: If you get this error on boot bonding:
wlan0 is up - this may be due to an out of date ifenslave

Then this is happening because the wpa_supplicant is being run before the failover netctl profile. This happens because systemd runs everything in parallel, unless told otherwise. ifenslave need all the interfaces to be down before bonding them to the bond0 interface. And, since the wpa_supplicant need to put the interface up to be able to scan for networks, this might cause the interface to not be enslaved and your bonding to only have the wired interface.

If this is your case, then you will need to setup a custom dependency on the wpa_supplicant@wlan0 service in relation with the netctl@failover profile. More specifically, the wpa_supplicant must be started after the netctl profile. To accomplish this, create a custom dependency file based on the instructions provided here: systemd#Handling dependencies

/etc/systemd/system/wpa_supplicant@wlan0.service.d/customdependency.conf
[Unit]
After=netctl@failover.service

After that you can try to reboot your system again and see if it works. You can check the status of your bonding by checking journalctl for the netctl@failover.service unit.

And by checking:

# ip link

You should see something like this:

1: eth0: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond0 state UP mode DEFAULT group default qlen 1000
    link/ether xx:xx:xx:xx:xx:xx brd ff:ff:ff:ff:ff:ff
2: wlan0: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc mq master bond0 state UP mode DORMANT group default qlen 1000
    link/ether xx:xx:xx:xx:xx:xx brd ff:ff:ff:ff:ff:ff
3: bond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default 
    link/ether xx:xx:xx:xx:xx:xx brd ff:ff:ff:ff:ff:ff

Now, you can test your failover setup, by initiating a big download. Unplug your wired interface. Your download should keep going over the wireless interface. Then, plug your wired interface again and it should keep working. You can debug by checking journalctl for the netctl@failover.service and wpa_supplicant@wlan0.service units.

Using any interface

In some cases it may be desirable to allow a profile to use any interface on the system. A common example use case is using a common disk image across many machines with differing hardware (this is especially useful if they are headless). If you use the kernel's naming scheme, and your machine has only one ethernet interface, you can probably guess that eth0 is the right interface. If you use udev's Predictable Network Interface Names, however, names will be assigned based on the specific hardware itself (e.g. enp1s0), rather than simply the order that the hardware was detected (e.g. eth0, eth1). This means that a netctl profile may work on one machine and not another, because they each have different interface names.

A quick and dirty solution is to make use of the /etc/netctl/interfaces/ directory. Choose a name for your interface alias (en-any in this example), and write the following to a file with that name (making sure it is executable).

/etc/netctl/interfaces/en-any
#!/bin/bash
for interface in /sys/class/net/en*; do
        break;
done
Interface=$(basename $interface)
echo "en-any: using interface $Interface";

Then create a profile that uses the interface. Pay special attention to the Interface directive. The rest are only provided as examples.

/etc/netctl/wired
Description='Wired'
Interface=en-any
Connection=ethernet
IP=static
Address=('192.168.1.15/24')
Gateway='192.168.1.1'
DNS=('192.168.1.1')

When the wired profile is started, any machine using the two files above will automatically bring up and configure the first ethernet interface found on the system, regardless of what name udev assigned to it. Note that this is not the most robust way to go about configuring interfaces. If you use multiple interfaces, netctl may try to assign the same interface to them, and will likely cause a disruption in connectivity. If you do not mind a more complicated solution, netctl-auto is likely to be more reliable.

Using hooks

netctl supports hooks in /etc/netctl/hooks/ and per interface hooks in /etc/netctl/interfaces/. You can set any option in a hook/interface that you can in a profile. They are read the same way! Most importantly this includes ExecUpPost and ExecDownPre.

When a profile is read, netctl sources all executable scripts in hooks, then it reads the profile file for the connection and finally it sources an executable script with the name of the interface used in the profile from the interfaces directory. Therefore, declarations in an interface script override declarations in the profile, which override declarations in hooks.

The variables $INTERFACE, $SSID, $ACTION and $Profile are available in hooks/interfaces only when using netctl-auto

Examples

Execute commands on established connection
/etc/netctl/hooks/myservices
#!/bin/sh
ExecUpPost="systemctl start crashplan.service; systemctl start dropbox@<username>.service"
ExecDownPre="systemctl stop crashplan.service; systemctl stop dropbox@<username>.service"
Activate network-online.target
/etc/netctl/hooks/status
#!/bin/sh
ExecUpPost="systemctl start network-online.target"
ExecDownPre="systemctl stop network-online.target"

Using this, systemd services requiring an active network connection can be ordered to start only after the network-online.target is reached, and can be stopped before the connection is brought down.

Set default DHCP client

To set or change the DHCP client used for all profiles:

/etc/netctl/hooks/dhcp
#!/bin/sh
DHCPClient='dhclient'

Alternatively, it may also be specified for a specific network interface by creating an executable file /etc/netctl/interfaces/<interface> with the following line:

DHCPClient='dhclient'

Tango-view-fullscreen.pngThis article or section needs expansion.Tango-view-fullscreen.png

Reason: It would be useful to replace the example with a general hook that executes different actions depending on $ACTION being CONNECT and DISCONNECT. (Discuss in Talk:Netctl#)

Minimal WPAConfigSection

As stated in the netctl.profile(5) man page, the WPAConfigSection variable is an array of config lines passed to wpa_supplicant. So, a minimal WPAConfigSection would contain:

Description='A wireless connection using a custom network block configuration'
Interface=wlan0
Connection=wireless
Security=wpa-configsection
IP=dhcp
WPAConfigSection=(
    'ssid="University"'
    'psk="very secret passphrase"'
)
Note: If trying to connect to an SSID with non-ASCII characters (unicode, emoji, etc), you can specify the SSID as hex instead of as a string, e.g. ssid=F09F90BA for "🐺". When unsure on the hex encoding, run wifi-menu (be sure to remove the \ and x characters).

Troubleshooting

Job for netctl@wlan(...).service failed

Warning: This section assumes that there is no other network service running before starting a netctl profile/service. See #Installation for details.

Some people have an issue when they connect to a network with netctl, for example:

# netctl start wlan0-ssid
Job for netctl@wlan0\x2ssid.service failed. See 'systemctl status netctl@wlan0\x2ssid.service' and 'journalctl -xn' for details.

When then looking at journalctl -xn, either of the following are shown:

1. If your device (wlan0 in this case) is up:

network[2322]: The interface of network profile 'wlan0-ssid' is already up

Setting the interface down should resolve the problem:

# ip link set wlan0 down

Then retry:

# netctl start wlan0-ssid

Tango-inaccurate.pngThe factual accuracy of this article or section is disputed.Tango-inaccurate.png

Reason: The following is an unsolved issue, using different DHCP client is just a poor/unexplained workaround. (Discuss in Talk:Netctl#)

2. If it is down:

dhcpcd[261]: wlan0: ipv4_sendrawpacket: Network is down

One way to solve this is to use a different DHCP client, for example dhclient. After installing the package configure netctl to use it:

/etc/netctl/wlan0-ssid
...
DHCPClient='dhclient'

Adding the ForceConnect option may also be helpful:

/etc/netctl/wlan0-ssid

...

ForceConnect=yes

Save it and try to connect with the profile:

# netctl start wlan0-ssid

dhcpcd: ipv4_addroute: File exists

On some systems dhcpcd in combination with netctl causes timeout issues on resume, particularly when having switched networks in the meantime. netctl will report that you are successfully connected but you still receive timeout issues. In this case, the old default route still exists and is not being renewed. A workaround to avoid this misbehaviour is to switch to dhclient as the default dhcp client. More information on the issue can be found here.

DHCP timeout issues

If you are having timeout issues when requesting leases via DHCP you can set the timeout value higher than netctl's 30 seconds by default. Create a file in /etc/netctl/hooks/ or /etc/netctl/interfaces/, add TimeoutDHCP=40 to it for a timeout of 40 seconds and make the file executable.

Connection timeout issues

If you are having timeout issues that are unrelated to DHCP (on a static ethernet connection for example), and are experiencing errors similar to the following when starting your profile:

# journalctl _SYSTEMD_UNIT=netctl@profile.service
Starting network profile 'profile'...
No connection found on interface 'eth0' (timeout)
Failed to bring the network up for profile 'profile'

Then you should increase carrier and up timeouts by adding TimeoutUp= and TimeoutCarrier= to your profile file:

/etc/netctl/profile
...
TimeoutUp=300
TimeoutCarrier=300

Do not forget to reenable your profile:

# netctl reenable profile

Problems with netctl-auto on resume

Sometimes netctl-auto fails to reconnect when the system resumes from suspend, hibernate or hybrid-sleep. An easy solution is to restart the service for netctl-auto. This can be automated with an additional service like the following:

/etc/systemd/system/netctl-auto-resume@.service
[Unit]
Description=restart netctl-auto on resume.
Requisite=netctl-auto@%i.service
After=sleep.target

[Service]
Type=oneshot
ExecStart=/usr/bin/systemctl restart netctl-auto@%i.service

[Install]
WantedBy=sleep.target

To enable this service for your wireless card, for example, enable netctl-auto-resume@wlan0.service as root. Change wlan0 to the required network interface.

If the device is not yet running on resume when the unit is started, this will fail. It can be fixed by adding the following dependency in the After line:

/etc/systemd/system/netctl-auto-resume@.service
...
After=sleep.target sys-subsystem-net-devices-%i.device
...

netctl-auto suddenly stopped working for WiFi adapters

This problem seems to be related to a recent wpa_supplicant update (see FS#44731), but a work-around is quite trivial. Just create a file for your interface (e.g. wlp3s0) in /etc/netctl/interfaces with the following content and make it executable:

/etc/netctl/interfaces/wlp3s0
WPAOptions="-m ''"

After that, try to restart your netctl-auto service and WiFi auto detection should work well again.

netctl-auto does not automatically unblock a wireless card to use an interface

Many laptops have a hardware button (or switch) to turn off wireless card, however, the card can also be blocked by the kernel. This can be handled by rfkill.

If you want netctl-auto to automatically unblock your wireless card to connect to a particular network, set RFKill=++auto++ option for the wireless connection of your choice, as specified in the netctl.profile(5) man page.

RTNETLINK answers: File exists (with multiple NICs)

This is a very misleading response, it really means that you have assigned a default gateway in an earlier netctl control file. When netctl starts up the n-th NIC and goes to set its local route, it fails because there is already a default route from n-1.

Remove it and everything works, except you no longer have a default route and so cannot access things such as the internet. ExecUpPost does not work as it gets executed for each network card.

A possible solution is creating a new service. Replace "FIRST_INTERFACE" and "SECOND_INTERFACE" with your interface names, and replace "192.168.xxx.yyy" with your default gateway.

/etc/systemd/system/defaultrouter.service
[Unit]
Description="Configure default gateway"
Requires=netctl@FIRST_INTERFACE.service netctl@SECOND_INTERFACE.service
After=netctl@FIRST_INTERFACE.service netctl@SECOND_INTERFACE.service

[Service]
Type=oneshot
ExecStart=/usr/bin/ip route add default via 192.168.xxx.yyy

[Install]
WantedBy=network-online.target

Problems with eduroam and other MSCHAPv2 connections

See WPA supplicant#Problems with eduroam and other MSCHAPv2 connections.

See also