Wireless USB Adapter 0bda:c811 Realtek Semiconductor Corp

Question

I am a bit lost sorting through the pile of documentation and Q&As about this topic so im just going to specifically ask.

I run an ASUS laptop, its a few years old and is unable to use 5ghz wifi, so i have use a usb wireless adapter (Flenco is the brand name, its just a standard 600mbps adapter, and no im not sure what serious of words and numbers anyone would need to identify it lol), to connect to the much faster wifi. on windows obviously no issue, plug and play etc. its the difference between 4-6 mbps download and 45-60mbps download.

I can not for the life of me get my linux to see it, and im too much of a noob to keep randomly messing up my system grasping at straws. It doesnt show up when i run lsusb, at least not under any name that would lead me down a fix path, not that i would know what to do from there anyways.

Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 004: ID 04ca:2006 Lite-On Technology Corp. Broadcom BCM43142A0 Bluetooth Device
Bus 001 Device 003: ID 04f2:b483 Chicony Electronics Co., Ltd 
Bus 001 Device 008: ID 05a7:1020 Bose Corp. 
Bus 001 Device 007: ID 04d9:a0f0 Holtek Semiconductor, Inc. 
Bus 001 Device 006: ID 1a40:0101 Terminus Technology Inc. Hub
Bus 001 Device 002: ID 0bda:c811 Realtek Semiconductor Corp. 
Bus 001 Device 005: ID 0c45:5004 Microdia 
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

I am completely positive this has been solved a hundred times over and I apologize for that, if someone could maybe point me towards a prior answer or offer a little more direct guidance that would be amazing.

I run Ubuntu 19.04, everything is up to date and working very well, just this issue.

Thanks!

Bus 001 Device 009: ID 0bda:c811 Realtek Semiconductor Corp. 
Couldn't open device, some information will be missing
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass            0 
  bDeviceSubClass         0 
  bDeviceProtocol         0 
  bMaxPacketSize0        64
  idVendor           0x0bda Realtek Semiconductor Corp.
  idProduct          0xc811 
  bcdDevice            2.00
  iManufacturer           1 
  iProduct                2 
  iSerial                 3 
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength       0x0035
    bNumInterfaces          1
    bConfigurationValue     1
    iConfiguration          0 
    bmAttributes         0xa0
      (Bus Powered)
      Remote Wakeup
    MaxPower              500mA
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           5
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass    255 Vendor Specific Subclass
      bInterfaceProtocol    255 Vendor Specific Protocol
      iInterface              2 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x84  EP 4 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0200  1x 512 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x05  EP 5 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0200  1x 512 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x06  EP 6 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0200  1x 512 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x87  EP 7 IN
        bmAttributes            3
          Transfer Type            Interrupt
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               3
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x08  EP 8 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0200  1x 512 bytes
        bInterval               0

this is the only entry that changed.

also, model number is X455L.

Looks like X455L is an incomplete model name; should have an extra letter or two after the L. You could have a X455LA, X455LAB, X455LB, X455LD, X455LDB, X455LF, X455LJ, X455LN, or X455LNB. Can you try https://www.asus.com/us/support/Article/565/ ? — K7AAY, Aug 02 '19 at 18:29
Discussion of WiFi card change at https://forums.tomshardware.com/threads/upgrading-notebook-wireless-combo.2857478/ and https://www.asus.com/US/support/FAQ/1037422 — K7AAY, Aug 02 '19 at 18:35
@mikewhatever https://askubuntu.com/questions/1089790/usb-wifi-realtek-not-an-mtp-device and see my answer below. — chili555, Aug 02 '19 at 20:24
@chili555 Glad you are on it. I don't have the device, but if it works, well, better later then never. — mikewhatever, Aug 02 '19 at 21:24
Guys we are saved! All you have to do is update to the 6.3 kernel and it works!! — user3413723, Jul 31 '23 at 09:30

chili555 · Answer 1 · 2021-12-09T15:15:19.367

54

The good news is that your 0bda:c811 device has support and has been the subject of several answers and duplicates here before; for example: USB WIFI Realtek not an MTP device The bad news is that the previous driver files will not properly compile on Ubuntu 19.04 using a 5.0.0-xx kernel version.

I recommend that you use another method. With a temporary working internet connection, open a terminal and do:

sudo apt update
sudo apt install build-essential git dkms bc
git clone https://github.com/brektrou/rtl8821CU.git
cd rtl8821CU
chmod +x dkms-install.sh
sudo ./dkms-install.sh

It builds successfully, albeit with a few possibly harmless warnings, on my 5.0.0-23 system

Next, do:

sudo modprobe 8821cu

Your wireless should now be working.

edited Dec 09 '21 at 15:15

answered Aug 02 '19 at 20:33

chili555

60,188

This worked great! Because I was working from a new install and didn't have an existing network connection, I was able to install dkms from the USB install media using the instructions here: https://askubuntu.com/a/1173564/18665 – bmaupin Mar 17 '20 at 13:20
Perfect, this worked 100% well on Ubuntu 18.04 LTS for me too. Thanks a ton! :-) – Jim C Apr 14 '20 at 13:19
2

Fails without bc, adding it to apt install command – Codebling Apr 21 '20 at 19:25
1

bc is installed as a part of build-essential and its dependencies libc6 and libc6-dev. It needn't be specified explicitly. – chili555 Apr 21 '20 at 20:09
Works great with Cudy AC 650 wireless USB stick (lsusb -> ID 0bda:c811 Realtek Semiconductor Corp. 802.11ac NIC). Ubuntu 20.04, Kernel 5.4. No problems at all. Follow the advice above and add "8821cu" to /etc/modules, so it will be loaded on the next boot. – apos May 30 '20 at 19:40
Didn't work for me unfortunately (same adapter, but HP Compaq): modprobe: FATAL: Module 8821cu not found. – Roger V. Nov 26 '20 at 13:01
1

@Vadim Please start your own new question and show the terminal output of the sudo ./dkms-install.sh command. I suspect that it does not complete correctly. – chili555 Nov 26 '20 at 15:50
1

Thanks! That made my day – Jorge Arévalo Jan 17 '21 at 23:00
3

For any who find this thread in a frustrating search for the fabled preexistng driver referenced elsewhere, ya just forget that; it doesn't exist. This is the best, easiest way to make the device work. Don't waste hours struggling, just do like this answer says and life will get a lot better. – u2n Apr 27 '21 at 18:57
1

Thanks so much @chili555, I tried so many variations of other stuff on the internet but this method made it work instantaneously. – AliF50 Jul 18 '21 at 18:08
1

Worked on 20.04.3 kernel 5.11.0-37-generic - thanks! – Jeff Ward Oct 15 '21 at 21:18
As a few comments above, I too was unable to complete the installation because the bc package was missing, evidently not installed with build-essential. – Teo7 Nov 11 '21 at 16:59
bc is evidently no longer a dependency of build-essential. I've amended my answer accordingly. – chili555 Dec 09 '21 at 15:14
BOOM - working. thx – johndpope Mar 15 '22 at 10:57
Just confirming that this still works with kernel 5.16.15, impish amd64. – twowheeler Apr 10 '22 at 00:05
2

great help. thank a lot. worked on ubuntu 20.04 kernel 5.13.0-39-generic – Ki Ko Apr 14 '22 at 23:53
As I reported in github there is an issue with kernel 5.17.9 . is there any update ? – Saeed Tabrizi May 19 '22 at 14:11

hellork · Answer 2 · 2023-11-12T02:13:50.330

2

It's 2023 and this driver is now included with kernel 6.3. For earlier kernels, there is an updated driver on https://github.com/morrownr/8821cu-20210916 that is rebuilt from a later version. It is continuously updated and builds with no errors or warnings.

Git clone https://github.com/morrownr/8821cu-20210916.git
cd 8821cu-20210916
sudo ./install-driver.sh

edited Nov 12 '23 at 02:13

answered Apr 16 '23 at 05:22

hellork

171

1

I just upgraded to a clean 22.04 and this solution failed silently. It required sudo apt install build-essential dkms, which took me a few reboots to notice. – John Jun 17 '23 at 18:09
1

If u update the kernel to 6.3 it is built in now. – user3413723 Jul 31 '23 at 09:30
1

To update kernel: sudo add-apt-repository ppa:cappelikan/ppa; sudo apt update; sudo apt install mainline; nice gui to update kernel w/o too much trouble or command line. sorry, it won't let me post an answer because I don't have enough rep lol :) so silly. – user3413723 Jul 31 '23 at 09:36
I have 22.04 and the latest 6.5 kernel. rtw8821cu worked well on 6.3. drops every ten minutes on 6.5 kernel. Installed the above driver and things are golden. Don't have ac speeds but that is far better than dropping. thanks morrownr whoever you are – walttheboss Mar 01 '24 at 07:52

Wireless USB Adapter 0bda:c811 Realtek Semiconductor Corp

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