Estoy usando Debian Jessie y cuando tecleo en la terminal ifconfig me sale el siguiente mensaje:
Could not find the database of available applications, run update-command-not-found as root to fix this
Command 'ifconfig' is available in '/sbin/ifconfig'
The command could not be located because '/sbin' is not included in the PATH environment variable.
This is most likely caused by the lack of administrative priviledges associated with your user account.
ifconfig: command not found


Para solucionarlo entramos a la terminal y tecleamos lo siguiente:
sudo nano ~/.bashrc


Agregamos en final de la linea:
export PATH=$PATH:/sbin


Guardamos el cambio (Control + 0) y luego cerramos el editor (Control + x). Volvemos a teclear en la terminal:
source ~/.bashrc


Volvemos a teclear en la terminal:
ifconfig


Y nos sale por pantalla:
docker0 Link encap:Ethernet HWaddr 2a:6c:51:38:cf:db
inet addr:172.17.42.1 Bcast:0.0.0.0 Mask:255.255.0.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:112 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:21173 (20.6 KiB)

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:528 errors:0 dropped:0 overruns:0 frame:0
TX packets:528 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:98600 (96.2 KiB) TX bytes:98600 (96.2 KiB)

wlan0 Link encap:Ethernet HWaddr 68:17:29:c0:fa:12
inet addr:192.168.0.7 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::6a17:29ff:fec0:fa12/64 Scope:Link
inet6 addr: ::6a17:29ff:fec0:fa12/64 Scope:Global
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:97341 errors:0 dropped:0 overruns:0 frame:0
TX packets:111205 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:136040749 (129.7 MiB) TX bytes:13355604 (12.7 MiB)