gigabyte56
Posts: 3
Joined: Mon Dec 28, 2015 6:26 pm

Help needed installing Wifi driver on Raspbian

Mon Mar 19, 2018 6:07 pm

After reading a number of different entries on this forum and elsewhere, I can see I need to install a device driver for my Edimax EW-7811Un Wireless USB adapter. Evidence:

uname -a gives: Linux rpi-raspbian 3.18.0-20-rpi2 #21-Ubuntu SMP PREEMPT Sun Apr 5 01:56:02 UTC 2015 armv7l GNU/Linux
lsusb gives: Bus 001 Device 004: ID 7392:7811 Edimax Technology Co., Ltd EW-7811Un 802.11n Wireless Adapter [Realtek RTL8188CUS]
lsmod gives an empty table. Apparently, it should have an entry for module 8192cu

When I search /lib/modules with find /lib/modules -name "8192cu*", I get the following 2 lines of output:

Code: Select all

/lib/modules/4.9.35-v7+/kernel/drivers/net/wireless/realtek/rtl8192cu/8192cu.ko
/lib/modules/4.9.35+/kernel/drivers/net/wireless/realtek/rtl8192cu/8192cu.ko
This suggests to me that the driver is installed, but I'm not a Linux expert! When I try running depmod -a, I get:

Code: Select all

depmod: ERROR: could not open directory /lib/modules/3.18.0-20-rpi2: No such file or directory
depmod: FATAL: could not search modules: No such file or directory
When I examine the root filesystem, I can confirm that there is no /lib/modules/3.18.0-20-rpi2 folder

Can someone point me in the right direction, please? Thanks.

Further background info:
The Pi had been working perfectly well for many months, then taken out of service for a few months. When I tried to get it working again on a new network, I was getting boot errors. This turned out to be because I had added another data HDD, which had probably been assigned to /dev/sda1, which wasn't bootable. I removed the new HDD, used wired ethernet, booted up ok, then did a full apt-get update/upgrade. All the outputs given above were after the system updates and reboot.

User avatar
topguy
Posts: 4567
Joined: Tue Oct 09, 2012 11:46 am
Location: Trondheim, Norway

Re: Help needed installing Wifi driver on Raspbian

Mon Mar 19, 2018 10:56 pm

You should not be running 3.18 of the kernel if you have the modules of 4.9.35 in your filesystem. Something has gone wrong and you have the wrong kernel on your boot-partition. I dont think anyone can help you install the driver for that kernel, but maybe someone has some idea to get you up to 4.9+

jamesh
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 19856
Joined: Sat Jul 30, 2011 7:41 pm

Re: Help needed installing Wifi driver on Raspbian

Tue Mar 20, 2018 9:56 am

Blimey - 3.18 is a fantastically old kernel.
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
Please direct all questions to the forum, I do not do support via PM.

gigabyte56
Posts: 3
Joined: Mon Dec 28, 2015 6:26 pm

Re: Help needed installing Wifi driver on Raspbian

Tue Mar 20, 2018 12:19 pm

Thanks jamesh and topguy.

Some more background: When I originally setup the pi, I put linux onto a USB drive, leaving the SD card in tact, except for a small change to cmdline.txt:

dwc_otg.lpm_enable=0 console=tty1 root=/dev/sda1 rootwait rootdelay=5

In my earlier post, I explained that I had been having boot problems. Thinking that I may have corrupted the image on the SD card (for device /dev/mmcblk0p1), I restored from an image file I'd kept on the PC. There is a small chance that this SD card image was not in fact from a Raspbian system, but from an Ubuntu system. Could this explain the anomaly? If so, is the situation recoverable?

gigabyte56
Posts: 3
Joined: Mon Dec 28, 2015 6:26 pm

Re: Help needed installing Wifi driver on Raspbian

Sat Mar 24, 2018 12:49 pm

I suspect I need some input from a Linux specialist to resolve this issue. If none is forthcoming, I'm going to have to re-install Raspbian, and start all over again, which I'm desperately trying to avoid!

k-pi
Posts: 441
Joined: Sun Feb 12, 2017 1:46 pm
Location: Upper Hale, Surrey, UK.

Re: Help needed installing Wifi driver on Raspbian

Sat Mar 24, 2018 2:29 pm

Likely best if you bring your system up to date by using the latest image of Rasbian.

(All modules have to match their kernels - if you are on a 3 series kernel you need the exact same 3 series modules.)

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