19

I am using Ubuntu 10.04 (LTS) on a Samsung N150+ netbook. I cannot scan wifi networks using iwlist and I would like to do so. Here is the output from some tests:

alex@alex-laptop:~/Desktop/GoogleCode$ iwlist eth1 scan
eth1      Interface doesn't support scanning.


alex@alex-laptop:~/Desktop/GoogleCode$ iwlist scan
lo        Interface doesn't support scanning.

eth0      Interface doesn't support scanning.

eth1      Interface doesn't support scanning.

pan0      Interface doesn't support scanning.

So I try iwconfig

alex@alex-laptop:~/Desktop/GoogleCode$ iwconfig
lo        no wireless extensions.

eth0      no wireless extensions.

eth1      IEEE 802.11  Access Point: Not-Associated   
      Link Quality:5  Signal level:207  Noise level:168
      Rx invalid nwid:0  invalid crypt:0  invalid misc:0

pan0      no wireless extensions.

I have a 05:00.0 Network controller: Broadcom Corporation Device 4727 (rev 01) from using lspci.

Any hints?

3
  • 4
    Did you try scanning as root?
    – jordanm
    Aug 12, 2012 at 23:06
  • @jordanm, this is a bit embarrassing but you are right that root was a necessary condition which I did not try. Could you put this as an answer?
    – Vass
    Aug 14, 2012 at 6:42
  • glad it helped. answer added.
    – jordanm
    Aug 14, 2012 at 16:31

7 Answers 7

16

You have to bring eth1 up before scanning.

ifconfig eth1 up

iwlist eth1 s

1
  • Being root or this didn't help me neither. But NetworkManager doesn't have any issue to scan the networks. Any idea ?
    – vaab
    Jan 15, 2015 at 4:57
5

The ability to scan using iwlist and associate to access points via iwconfig require root. In Ubuntu you can use the following:

sudo iwlist eth1 scan
2
  • 1
    Thanks. For me that does not resolve the issue. Would you have any other suggestion? Aug 3, 2014 at 15:23
  • for people as confused as i am, this may happen: on my arch system, sudo iw eth1 scan fails but sudo iwlist eth1 scan succeeds
    – Francois
    Mar 30, 2016 at 15:00
5

If you have checked that you are root and your device is up:

sudo ifconfig eth1 up && sudo iwlist eth1 scan

And it still doesn't work, I found that:

iw dev wlan0 scan ap-force

Would work in my case. It seems that iwlist tool is obsolete and not anymore supported for recent wifi chipset.

1
  • Using the same tool: iw wlan0 scan
    – aleb
    Jan 24, 2018 at 14:32
4

Check rfkill list all

Mine had the following output

0: phy0: Wireless LAN
Soft blocked: yes
Hard blocked: no

Which was causing the error Interface doesn't support scanning

To remove the block simply run the following command

sudo rfkill unblock wifi
3

This issue can be also be caused by the wireless interface (I'll use wlan0 - not eth1) being in the wrong mode. To fix this you can use:

sudo ifconfig wlan0 down
sudo iwconfig wlan0 mode Managed
sudo ifconfig wlan0 up
sudo iwlist wlan0 scan

You have to bring down the interface before changing the mode to prevent the interface being classified as busy.

2

have you checked the interface name with command

ifconfig

and you can do ifconfig "interface-name" up
by example: for my wireless interface

ifconfig wlp2s0 up

the next thing to do is:

iwlist wlp2s0 scan
2

On Debian testing/bookworm ifconfig is not present. To bring the interface up you have to type as root (my interface name is wlp1s0b1):

ip link set wlp1s0b1 up

and now you can scan:

/sbin/iwlist wlp1s0b1 scan | grep -i ssid

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