Quelques outils de dépannage en cas de problème Wifi... sur Ubuntu et dérivés et sur Debian.

Commande inxi

Permet d'obtenir des informations détaillées sur la machine, commande disponible sous Ubuntu et dérivés.

$ inxi -Fxz
System:    Host: Marc-ThinkPad-SL510 Kernel: 4.4.0-53-generic x86_64 (64 bit gcc: 5.4.0)
           Desktop: KDE Plasma 5.8.7 (Qt 5.6.1) Distro: Linux Mint 18.1 Serena
Machine:   System: LENOVO product: 5072W18 v: ThinkPad SL510
           Mobo: LENOVO model: 5072W18 Bios: LENOVO v: 6JET85WW (1.43 ) date: 12/24/2010
CPU:       Dual core Intel Core2 Duo T6670 (-MCP-) cache: 2048 KB
           flags: (lm nx sse sse2 sse3 sse4_1 ssse3 vmx) bmips: 8777
           clock speeds: max: 2201 MHz 1: 1600 MHz 2: 1600 MHz
Graphics:  Card: Intel Mobile 4 Series Integrated Graphics Controller bus-ID: 00:02.0
           Display Server: X.Org 1.18.4 drivers: intel (unloaded: fbdev,vesa) Resolution: 1366x768@60.00hz
           GLX Renderer: Mesa DRI Mobile Intel GM45 Express GLX Version: 2.1 Mesa 17.0.7 Direct Rendering: Yes
Audio:     Card Intel 82801I (ICH9 Family) HD Audio Controller driver: snd_hda_intel bus-ID: 00:1b.0
           Sound: Advanced Linux Sound Architecture v: k4.4.0-53-generic
Network:   Card-1: Realtek RTL8191SEvB Wireless LAN Controller driver: rtl8192se port: 2000 bus-ID: 05:00.0
           IF: wlp5s0 state: down mac: 
           Card-2: Realtek RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
           driver: r8169 v: 2.3LK-NAPI port: 4000 bus-ID: 08:00.0
           IF: enp8s0 state: up speed: 100 Mbps duplex: full mac: 
Drives:    HDD Total Size: 250.1GB (34.9% used) ID-1: /dev/sda model: WDC_WD2500BEVT size: 250.1GB
Partition: ID-1: / size: 224G used: 76G (36%) fs: ext4 dev: /dev/sda1
           ID-2: swap-1 size: 6.27GB used: 0.07GB (1%) fs: swap dev: /dev/sda5
RAID:      No RAID devices: /proc/mdstat, md_mod kernel module present
Sensors:   System Temperatures: cpu: 45.0C mobo: 0.0C
           Fan Speeds (in rpm): cpu: N/A fan-1: 655
Info:      Processes: 238 Uptime: 2 days Memory: 3111.5/5807.1MB Init: systemd runlevel: 5 Gcc sys: 5.4.0
           Client: Shell (bash 4.3.481) inxi: 2.2.35

Pour les interfaces réseau lshw

lshw -C Network
  *-network               
       description: Ethernet interface
       produit: RTL8101/2/6E PCI Express Fast/Gigabit Ethernet controller
       fabriquant: Realtek Semiconductor Co., Ltd.
       identifiant matériel: 0
       information bus: pci@0000:01:00.0
       nom logique: enp1s0
       version: 02
       numéro de série: 
       taille: 10Mbit/s
       capacité: 100Mbit/s
       bits: 64 bits
       horloge: 33MHz
       fonctionnalités: pm msi pciexpress msix vpd bus_master cap_list rom ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd autonegotiation
       configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=half latency=0 link=no multicast=yes port=MII speed=10Mbit/s
       ressources: irq:26 portE/S:d000(taille=256) mémoire:ffd10000-ffd10fff mémoire:ffd00000-ffd0ffff mémoire:dfd00000-dfd1ffff
  *-network DÉSACTIVÉ
       description: Interface réseau sans fil
       produit: RT2790 Wireless 802.11n 1T/2R PCIe
       fabriquant: Ralink corp.
       identifiant matériel: 0
       information bus: pci@0000:02:00.0
       nom logique: wlp2s0
       version: 00
       numéro de série: 
       bits: 32 bits
       horloge: 33MHz
       fonctionnalités: pm msi pciexpress bus_master cap_list ethernet physical wireless
       configuration: broadcast=yes driver=rt2800pci driverversion=4.4.0-53-generic firmware=N/A latency=0 link=no multicast=yes wireless=IEEE 802.11bgn
       ressources: irq:17 mémoire:dfc00000-dfc0ffff
  *-network
       description: Ethernet interface
       identifiant matériel: 1
       nom logique: enx0c5b8f279a64
       numéro de série: 
       fonctionnalités: ethernet physical
       configuration: broadcast=yes driver=cdc_ether driverversion=22-Aug-2005 firmware=CDC Ethernet Device ip=192.168.100.100 link=yes multicast=yes

Analyser les périphériques pci est également instructif

lspci -nn
00:00.0 Host bridge [0600]: Intel Corporation Mobile 945GSE Express Memory Controller Hub [8086:27a] (rev 03)
00:02.0 VGA compatible controller [0300]: Intel Corporation Mobile 945GSE Express Integrated Graphics Controller [8086:27a] (rev 03)
00:02.1 Display controller [0380]: Intel Corporation Mobile 945GM/GMS/GME, 943/940GML Express Integrated Graphics Controller [8086:27a6] (rev 03)
00:1b.0 Audio device [0403]: Intel Corporation NM10/ICH7 Family High Definition Audio Controller [8086:27d8] (rev 02)
00:1c.0 PCI bridge [0604]: Intel Corporation NM10/ICH7 Family PCI Express Port 1 [8086:27d0] (rev 02)
00:1c.1 PCI bridge [0604]: Intel Corporation NM10/ICH7 Family PCI Express Port 2 [8086:27d2] (rev 02)
00:1d.0 USB controller [0c03]: Intel Corporation NM10/ICH7 Family USB UHCI Controller #1 [8086:27c8] (rev 02)
00:1d.1 USB controller [0c03]: Intel Corporation NM10/ICH7 Family USB UHCI Controller #2 [8086:27c9] (rev 02)
00:1d.2 USB controller [0c03]: Intel Corporation NM10/ICH7 Family USB UHCI Controller #3 [8086:27c] (rev 02)
00:1d.3 USB controller [0c03]: Intel Corporation NM10/ICH7 Family USB UHCI Controller #4 [8086:27cb] (rev 02)
00:1d.7 USB controller [0c03]: Intel Corporation NM10/ICH7 Family USB2 EHCI Controller [8086:27c] (rev 02)
00:1e.0 PCI bridge [0604]: Intel Corporation 82801 Mobile PCI Bridge [8086:2448] (rev e2)
00:1f.0 ISA bridge [0601]: Intel Corporation 82801GBM (ICH7-M) LPC Interface Bridge [8086:27b9] (rev 02)
00:1f.2 SATA controller [0106]: Intel Corporation 82801GBM/GHM (ICH7-M Family) SATA Controller [AHCI mod] [8086:27c5] (rev 02)
01:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8101/2/6E PCI Express Fast/Gigabit Ethernet controller [10ec:8136] (rev 02)
02:00.0 Network controller [0280]: Ralink corp. RT2790 Wireless 802.11n 1T/2R PCIe [1814:0781]

On peut également récupérer des informations sur le module du noyau associé au périphérique.

modinfo rt2800pci
filename:       /lib/modules/4.4.0-53-generic/kernel/drivers/net/wireless/rt2x00/rt2800pci.ko
license:        GPL
firmware:       rt2860.bin
description:    Ralink RT2800 PCI & PCMCIA Wireless LAN driver.
version:        2.3.0
author:         http://rt2x00.serialmonkey.com
srcversion:     26CCED9E0CE5EFBFA9B8882
[...snip...] (je fais sauter la suite des alias qui est trop longue)
depends:        rt2x00lib,rt2800lib,rt2800mmio,rt2x00mmio,rt2x00pci,eeprom_93cx6
intree:         Y
vermagic:       4.4.0-53-generic SMP mod_unload modversions 686
parm:           nohwcrypt:Disable hardware encryption. (bool)

Configuration réseau wifi avec ifwconfig

iwconfig

lo        no wireless extensions.

enp1s0    no wireless extensions.

enx0c5b8f279a64  no wireless extensions.

wlp2s0    IEEE 802.11bgn  ESSID:off/any 
          Mode:Managed  Access Point: Not-Associated   Tx-Power=off   
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:off

Voir les blocages matériels ou logiciels du wifi

rfkill list

2: phy0: Wireless LAN
   Soft blocked: yes
   Hard blocked: yes

Dans cet exemple la carte est bloquée matériellement (par un interrupteur, ou une combinaison de touches clavier, et logiciellement bloquée. Avec la commande :

rfkill unblock 2

rfkill list

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

on peut débloquer la carte logiciellement, pour le blocage matériel il faut actionner l'interrupteur.