Linux Disconnect Network and Connect Again Command Line

Question

This applies to 12.04+ since these are the ones I could exam simply could too be used in older versions. I have separated this guide into several parts, which consist of:

Part one Wireless Routers with no password or WEP Key
Function ii Wireless Routers with WPA or WPA2 security Cardinal
- Part ii.ane Connecting to a WPA Router with wpa_supplicant
- Office 2.2 Connecting to a WPA Router with Network Manager
Part iii Like shooting fish in a barrel Connectedness Via nmcli
Function 4 Disconnecting from a Wireless Router
Part 5 Deleting a Connexion (Including Configuration File)
Function 6 Automated connection when login in
Bonus How to discover your network interface name via GUI

The following control lines can exist used to connect and disconnect depending on the Wireless card, wireless security and wireless router settings. Before proceeding, brand certain the network service is enabled (For cases where you might beginning Ubuntu using Recovery mode):

Depending on your Ubuntu Version, you would need to start it using i of the post-obit way:

If using SystemD (since 14.10+):

          sudo systemctl get-go networking

If using the Legacy init.d style: sudo /etc/init.d/networking restart

If using the Legacy Upstart way: sudo service network-manager restart

Part i: Wireless Routers with no countersign or WEP Key

For cases where the wireless router has no password or WEP security, practise the following:

Open the concluding and lookup for the wireless connection:
```
              iwlist wlan0 s                          
```
(The due south is for Scan. wlan0 is my wireless carte du jour just could exist different for each user. Some take eth0, others wlan2.. You demand sudo to execute this option.To find out the name of your wireless card simply type iwlist and press TAB. This should autocomplete the line with the network card'south name. You can also blazon iwconfig and find the name on the list that will show.)

If you practise not know the proper noun of your wireless devices type: iwconfig which volition show y'all your wired/wireless devices and their names. They might be something like wlan0, wlan1, eth1, eth2..
The lookup will show y'all all possible Admission Points (AP) visible to yous. After you meet your router in the list effort to connect to it:

If it does not have a password practice the following:
```
              iwconfig wlan0 essid NAME_OF_ACCESS_POINT                          
```
For example
```
              iwconfig wlan0 essid CYREX                          
```
subsequently that, make certain to utilise dhclient then you can become a dynamic IP in case you lot don't become assigned one by the router. That should leave yous connected to the CYREX router.

If it has a password and so practise:
```
              iwconfig wlan0 essid CYREX key PASSWORD                          
```
That should connect using the PASSWORD you gave there.

Once again, do dhclient after connecting to make sure you get an IP assigned.
Making certain yous are correctly connected is always good then execute iwconfig to make sure your wireless card is connected to the SSID you mentioned above. It should testify your device connected and the IP assigned to you lot. If information technology does not and gives yous an error similar Interface doesn't support scanning try the post-obit 2 options:
- Test if your interface is UP: sudo ifconfig wlan0 up
- Try adding sudo when doing the scan: sudo iwlist wlan0 s
- Try bringing the device down and and so back upwardly:
```
                  sudo ifconfig wlan0 down   sudo ifconfig wlan0 upwardly                                  
```

Role ii: Wireless Routers with WPA or WPA2 security Primal

For cases where the wireless router has a WPA/WPA2 password in that location are a few ways of doing this. I volition mention the ii most popular ones::

Open the terminal and lookup for the wireless connectedness:
```
              iwlist wlan0 s                          
```
(The s is for Scan. wlan0 is my wireless card but could exist different for each user. Some have eth0, others wlan2.. Yous need sudo to execute this option. To find out the proper name of your wireless card but blazon iwlist and press TAB. This should autocomplete the line with the network card'due south name. You tin also type iwconfig and observe the proper noun on the listing that volition show.)

If yous do not know the proper name of your wireless devices type: iwconfig which will show you your wired/wireless devices and their names. They might be something similar wlan0, wlan1, eth1, eth2..
The lookup will show you all possible Access Points (AP) visible to yous. After you see your router in the list try to connect to it:

Part 2.1 WPA-SUPPLICANT GUIDE: Connecting to a WPA Router with wpa_supplicant

Type the following in the terminal (Assuming you accept the wpasupplicant package installed which installs all the needed commands we will use here):
```
              wpa_passphrase SSID PASSWORD > CONFIG_FILE                          
```
Example: wpa_passphrase Virus LinuxFTW > wpa.conf

Where Virus is the proper name of my router,LinuxFTW is my password and wpa.conf is the file where I want to store all of this data in. Note that you can save the file in another place, many users save the file in /etc/wpa_supplicant.conf instead of wpa.conf. The information of the wpa.conf file should exist something like this:
```
              network={           ssid="Virus"           #psk="LinuxFTW"           psk=1d538d505f48205589ad25b2ca9f52f9cbb67687e310c58a8dd940ccc03fbfae   }                          
```
Up to this point, we should know the proper name of our wireless carte du jour interface (eg: Wlan0, eth2, Wlan2...). We now need to know which Driver is in apply. for this we type:
```
              wpa_supplicant                          
```
It should evidence us a lot of information, but there volition be a department chosen **Drivers* which shows all available drivers (These are available when compiling wpa_supplicant). In my case information technology is like this:
```
              drivers:     wext = Linux wireless extensions (generic)     nl80211 = Linux nl80211/cfg80211     wired = Wired Ethernet driver     none = no driver (RADIUS server/WPS ER)                          
```
The whole list is hostap, hermes, madwifi, wext, broadcom, wired, roboswitch, bsd, ndis. This can change depending on how wpa_supplicant was compiled, only the i that shows for me should be similar to the one on your system. Most users will select the wext driver.
So now that we have our wireless interface card name and the driver proper name, we proceed to connect to information technology using the already created configuration file using the following format:
```
              wpa_supplicant -iINTERFACE_NAME -cCONFIGURATION_FILE -DDRIVER_NAME                          
```
For example:
```
              wpa_supplicant -iwlan0 -c/etc/wpa_supplicant.conf -Dwext                          
```
Where -i is your interface carte's proper name, -c is where your configuration file is and -D is the proper noun of the driver you volition be using to connect. If it connects correctly, then we press CTRL+C to cancel it and then execute the line again only this time nosotros send it to the background with -B and then we can continue to use the terminal:
```
              wpa_supplicant -B -iwlan0 -c/etc/wpa_supplicant.conf -Dwext                          
```
After that merely practise a sudo dhclient wlan0 to get an IP from the router.

Some users accept reported removing the Hash and leaving only the password in the config, for example:

                              network={               ssid="Virus"               psk="LinuxFTW"       }

Others have added the ssid_scan to the config file:

                              network={               ssid="Virus"             scan_ssid=1               #psk="LinuxFTW"               psk=1d538d505f48205589ad25b2ca9f52f9cbb67687e310c58a8dd940ccc03fbfae       }

Or even calculation the Key blazon:

                              network={               ssid="Virus"             scan_ssid=1               key_mgmt=WPA-PSK             #psk="LinuxFTW"               psk=1d538d505f48205589ad25b2ca9f52f9cbb67687e310c58a8dd940ccc03fbfae       }

More than data almost this in man wpa_supplicant.conf

Part 2.2 NETWORK MANAGER GUIDE: Connecting to a WPA Router with Network Manager

The practiced thing about network manager is that information technology comes with a couple of nice scripts and tools. Two of these are nmcli and create_connection (Neat Python 3 script) which we will utilize in this case.

Afterwards doing the steps mentioned previously to detect your router's SSID proper name (Remember the part about iwlist above) nosotros practise the following:

              sudo /usr/share/checkbox/scripts/create_connection -South SECURITY_TYPE -One thousand PASSWORD SSID_NAME

Where SECURITY is the blazon of security the Router uses (WPA, WEP), PASSWORD is.. well..the password and SSID_NAME is the SSID Name of the Router. For example:

              sudo /usr/share/checkbox/scripts/create_connection -South wpa -K LinuxFTW Virus

Will create a connexion for Network Manager which should wait something similar this:

                              $ sudo /usr/share/checkbox/scripts/create_connection -South wpa -One thousand LinuxFTW Virus   [sudo] countersign for cyrex:    Connection Virus registered   Connection Virus activated.

Later on this, yous should get an IP assigned from the router. If not simply do sudo dhclient wlan0 (Assuming wlan0 is the name of your interface). Yous can also cheque your network manager's connections using nmcli similar this: nmcli c which should bear witness something like this:

                              $ nmcli c   Proper name                      UUID                                   TYPE              TIMESTAMP-REAL                       Xcentral                  f51a5a64-8a91-47d6-897c-28efcd84d2b0   802-eleven-wireless   Friday 22 Mar 2013 02:25:54 PM VET      Realtek                   9ded7740-ad29-4c8f-861f-84ec4da87f8d   802-3-ethernet    Tue 05 Mar 2013 01:xviii:31 AM VET      Intel                     e25b1fd8-c4ff-41ac-a6bc-22620296f01c   802-three-ethernet    Friday 05 April 2013 10:04:05 PM VET      Virus                     3f8ced55-507b-4558-a70b-0d260441f570   802-11-wireless   Tue 09 April 2013 06:31:x AM VET

I mention the Network Director'due south style because there are a couple of cases where using wpa_supplicant will simply not work (Problems between router and wireless card, security bug, etc..). In my case, all attempts to use wpa_supplicant on one PC did not piece of work, simply in another it worked the beginning time I tried. And so am posting both methods to assist on each case and to go far easier for users to decide which one they want.

Part 3: Like shooting fish in a barrel Connection via nmcli

Although we have talked about the ways to connect to it without a network manager, there is also the example of using nmcli (CLI version of the network manager) when information technology applies. To do this, nosotros do the post-obit:

Check to see which ESSID we can see:

              nmcli dev wifi

Verify the name of the ESSID and nosotros continue on using it on the next line including the password needed for it (This includes WEP and WPA type passwords):
```
              nmcli dev wifi connect ESSID_NAME password ESSID_PASSWORD                          
```
Here is an example of me connecting to the ESSID Linux5G

If you have multiple wireless devices on your figurer, you can specify which one to utilize using the ifname parameter like so:

nmcli dev wifi connect ESSID_NAME password ESSID_PASSWORD ifname WIRELESS_DEVICE_NAME

For example in my case the name of the device is wlp9s0 so I would utilize this line to specify the device that I will use to connect with:

More data most nmcli can be obtained past using the help parameter. For example if you wanted to know well-nigh nigh nmcli dev yous would type nmcli dev help. If yous wanted to know more than near nmcli dev wifi, y'all would type nmcli dev wifi help and so on.

Part 4: Disconnecting from a Wireless Router

In that location are several ways of accomplishing this:

Disconnect by "force": sudo ifconfig wlan0 down

This will turn your wireless carte du jour interface off (Driver turns off). To plow in on simply type ifconfig wlan0 up followed by a sudo dhclient wlan0. It will all the same show as connected if viewed by Network Director but there will actually be no connexion to the router. Trying to ping volition throw an connect: Network is unreachable fault.
Release the DHCP IP: sudo dhclient -r wlan0

Call back to do sudo dhclient wlan0 to assign yourself an IP again.
Disconnect using Network Manager: nmcli nm enable faux

Where nm is the parameter of nmcli that manages and sets Network Manager's states. The option enable tin be truthful or imitation, meaning if set to fake, all network connections managed by Network Director volition be disconnected. note that nmcli does not need root permissions.

To come across the status of Network Manager blazon nmcli nm, it should show something similar to this:

                      $ nmcli nm       RUNNING         STATE           WIFI-HARDWARE   WIFI       WWAN-HARDWARE   WWAN             running         connected       enabled         enabled    enabled         enabled

Another mode of turning the Connection On or Off (Connecting/Disconnecting) is by doing the following:

          nmcli c down id Proper name` - Volition disconnect the connection NAME    nmcli c up id Proper name` - Volition connect the connection NAME

Part 5: Deleting a Connexion

To delete an existing connectedness is adequately like shooting fish in a barrel. First type in the terminal:

          nmcli c

It volition output something like this:

          $ nmcli c NAME                      UUID                                   Blazon              TIMESTAMP-Real                     Realtek                   9ded7740-ad29-4c8f-861f-84ec4da87f8d   802-iii-ethernet    Tue 05 Mar 2013 01:eighteen:31 AM VET    PrivateSys                86b2b37d-4835-44f1-ba95-46c4b747140f   802-xi-wireless   Sun 21 Apr 2013 07:52:57 PM VET    pepe                      9887664b-183a-45c0-a81f-27d5d0e6d9d8   802-xi-wireless   Thu eighteen Apr 2013 02:43:05 AM VET    Virus                     3f8ced55-507b-4558-a70b-0d260441f570   802-xi-wireless   Tue 16 April 2013 11:33:24 AM VET    Intel                     e25b1fd8-c4ff-41ac-a6bc-22620296f01c   802-three-ethernet    Sun 21 Apr 2013 08:12:29 PM VET    Xcentral                  f51a5a64-8a91-47d6-897c-28efcd84d2b0   802-11-wireless   Fri 22 Mar 2013 02:25:54 PM VET

Now let us say nosotros want to delete Xcentral, we and so proceed with the following command:

          nmcli c delete id Xcentral

Later doing it should look something similar this:

          $ nmcli c delete id Xcentral $ nmcli c NAME                      UUID                                   Blazon              TIMESTAMP-Real                     Realtek                   9ded7740-ad29-4c8f-861f-84ec4da87f8d   802-3-ethernet    Tue 05 Mar 2013 01:eighteen:31 AM VET    PrivateSys                86b2b37d-4835-44f1-ba95-46c4b747140f   802-11-wireless   Sun 21 Apr 2013 07:52:57 PM VET    pepe                      9887664b-183a-45c0-a81f-27d5d0e6d9d8   802-11-wireless   Thu 18 Apr 2013 02:43:05 AM VET    Virus                     3f8ced55-507b-4558-a70b-0d260441f570   802-11-wireless   Tue 16 Apr 2013 11:33:24 AM VET    Intel                     e25b1fd8-c4ff-41ac-a6bc-22620296f01c   802-3-ethernet    Sunday 21 Apr 2013 08:12:29 PM VET

All connections are stored in /etc/NetworkManager/organisation-connections/

If I were to look in that folder right at present I would see the following files:

          $ ls /etc/NetworkManager/system-connections Intel  pepe  PrivateSys  Realtek  Virus

This is but in example you lot wish to edit/delete/add a connection past paw.

Function half-dozen: Automatic connection when login in

For cases where you would similar to login automatically to a wireless router here are the steps:

Open the interface file:

              sudo nano /etc/network/interfaces

Add together the following data (Assuming your interface is called wlan0):

              auto wlan0 iface wlan0 inet static address ASSIGNED_IP netmask 255.255.255.0 gateway THE_GATEWAY wireless-essid YOURSSID wireless-central WIRELESSKEY_HERE

Relieve the file and reboot computer. Note that this will exist saved on a plain text file which tin can be accessed from the same computer.

Bonus: Find your wireless connection's name GUI Style

Click on the Network Manager and go to Connection Information
Go to the Tab that holds your wireless menu

In this paradigm, this network card is named eth1 (Inside the parenthesis) but this can be different for each user. Ordinarily it would be a wlan (Like wlan0, wlan1, wlan2...) merely information technology tin also be eth1, eth2, etc.. Then yous need to encounter what name information technology has.

Another way to find the name quickly is by typing iwconfig which will testify all the wireless network card available.

Aitken Bovestesin