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This is the second time an update within 20.04 has stopped the mercusys wifi AC650 from working for me (the first time in the first week of using Ubuntu). I have now plugged in a wire to get the internet back working. The previous time I received a successful resolution here; Using a Mercusys AC650 usb wifi on in Ubuntu 20.04

Following the advice previously I tried;

cd build
cd rtl8821CU
make clean
sudo ./dkms-install.sh

The result of the make clean was;

#make -C /lib/modules/5.11.0-25-generic/build M=/home/fred/build/rtl8821CU clean
cd hal ; rm -fr */*/*/*.mod.c */*/*/*.mod */*/*/*.o */*/*/.*.cmd */*/*/*.ko
cd hal ; rm -fr */*/*.mod.c */*/*.mod */*/*.o */*/.*.cmd */*/*.ko
cd hal ; rm -fr */*.mod.c */*.mod */*.o */.*.cmd */*.ko
cd hal ; rm -fr *.mod.c *.mod *.o .*.cmd *.ko
cd core ; rm -fr */*.mod.c */*.mod */*.o */.*.cmd */*.ko
cd core ; rm -fr *.mod.c *.mod *.o .*.cmd *.ko
cd os_dep/linux ; rm -fr *.mod.c *.mod *.o .*.cmd *.ko
cd os_dep ; rm -fr *.mod.c *.mod *.o .*.cmd *.ko
cd platform ; rm -fr *.mod.c *.mod *.o .*.cmd *.ko
rm -fr Module.symvers ; rm -fr Module.markers ; rm -fr modules.order
rm -fr *.mod.c *.mod *.o .*.cmd *.ko *~
rm -fr .tmp_versions

Then I ran sudo ./dkms-install.sh;

[sudo] password for **:

About to run dkms install steps...
Error! DKMS tree already contains: rtl8821CU-5.4.1
You cannot add the same module/version combo more than once.


Kernel preparation unnecessary for this kernel.  Skipping...


Building module:
cleaning build area...
'make' KVER=5.11.0-25-generic......................(bad exit status: 2)
ERROR (dkms apport): binary package for rtl8821CU: 5.4.1 not found
Error! Bad return status for module build on kernel: 5.11.0-25-generic (x86_64)
Consult /var/lib/dkms/rtl8821CU/5.4.1/build/make.log for more information.


Kernel preparation unnecessary for this kernel.  Skipping...


Building module:
cleaning build area...
'make' KVER=5.11.0-25-generic......................(bad exit status: 2)
ERROR (dkms apport): binary package for rtl8821CU: 5.4.1 not found
Error! Bad return status for module build on kernel: 5.11.0-25-generic (x86_64)
Consult /var/lib/dkms/rtl8821CU/5.4.1/build/make.log for more information.
Finished running dkms install steps.

So I noticed that dkms status was also suggested so I ran;

dkms status
rtl8192eu, 1.0: added
rtl8821CU, 5.4.1, 5.8.0-63-generic, x86_64: installed

Please advise on how to proceed to have the Mercusys AC650 back operational so I don't have a wired connection to use the internet?

Peter
  • 3
  • If you boot into your older kernel, does your wireless work? – user535733 Aug 06 '21 at 19:12
  • Thanks for the tip unfortunately I do not know how I make this change! How do I go about trying this out? Thanks. – Peter Aug 06 '21 at 20:07
  • How to boot into an older kernel: https://askubuntu.com/questions/82140/how-can-i-boot-with-an-older-kernel-version – user535733 Aug 06 '21 at 20:11
  • Okay, thanks, yes I pressed the shift key during boot sequence and got into GRUB. There I selected Advanced options for Ubuntu, once in there I could select 5.11.0.-25-generic or 5.11.0.-25-generic (recovery mode) then either 5.8.0-63-generic or 5.8.0-63-generic (recovery mode). I selected 5.8.0-63-generic option and my wifi came back on working and I took out the wire and still have internet! Selecting 5.11.0.-25-generic the wifi will still not work though. Thanks for your assistance I suppose I could try keeping this older kernel? – Peter Aug 06 '21 at 20:43
  • Sure, you can keep booting into that older kernel temporarily. Beware: Your system will automatically delete older kernels, but not the running kernel. Someday you may boot into the newer kernel...and the old one will vanish. Get into the habit of rebuilding your wi-fi driver for new kernel releases. to avoid a nasty surprise. Most wi-fi hardware does not require manual rebuilding of drivers -- your case is unfortunate, and it's Realtek's fault. – user535733 Aug 06 '21 at 21:33
  • Hello again. I am now wondering about buying a new usb wifi that is more suited to Ubuntu. This is after seeing if a new kernel resolved this overall issue which it did not. Could you advise a product that will be more software compatible - ideally one with a large antenna as this Mercusys is? Thanks. – Peter Aug 30 '21 at 16:29
  • Unfortunately, we do not make hardware recommendations. We are volunteers, and do not have access to a large stock of hardware to test. You can try https://ubuntu.com/certified, which does list hardware tested by professional Canonical engineers. However, that list is not exhaustive nor complete; it's just what some OEMs submit for testing. – user535733 Aug 30 '21 at 16:39
  • Okay thanks for the reply. There are google linux compatible usb wifi that are recommended I shall try one of these if they are not too expensive. – Peter Aug 30 '21 at 16:49
  • Hello. I did buy another wifi usb which was recommended in their description on Amazon for use for Linux specifically saying suitable for Ubuntu 20.04. This is the BrosTrend AC650 Dual Band Long Range USB Wi-Fi Adapter Model No: AC5L For Linux. It installed just fine after following the instructions in the CD that came in the packaging which gave the commands to type into Terminal as long as you are connected with wire to install. So I am now back on the internet only wireless. – Peter Sep 01 '21 at 19:05

0 Answers0