root@ubuntu:~# iwconfig
wlan0     IEEE 802.11bg  ESSID:"angee-office"
          Mode:Managed  Frequency:2.472 GHz  Access Point: 58:6D:8F:F2:86:4C
          Bit Rate=18 Mb/s   Tx-Power=20 dBm
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:off
          Link Quality=42/100  Signal level=42/100
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:1  Invalid misc:11   Missed beacon:0

lo        no wireless extensions.

eth0      no wireless extensions.

root@ubuntu:~# dhclient -v wlan0
Internet Systems Consortium DHCP Client 4.2.4
Copyright 2004-2012 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/

Can't allocate interface etlease {
  interface .
root@ubuntu:~#