problem in installing Big Sur 11.3

Suggest - restart Router and then Shutdown Computer and connect via Ethernet connection. Restart computer in Safe Mode - Shift - Key immediately at startup. It does a Repair Disk, clears cache files and load only Apple Software - load slowly - Normal. Once in Open Apple Apps Store and find Big Sur and download. Try not to let computer go to sleep mode or Screen Save to activate. Be patient as one knows it Big Sur is 12.18 GB size. There are often periods where it seems to pause the download , normal be patient as countdown clock may say 15 minutes but in Real Time could be 30 - 45 minutes. This can and will happen several time in the process. If all goes well. it will successfully download and attempt to Launch. Do NOT allow it to start - Quit the Installer. Check Applications Folder for new App called Install Bug Sur. Make a copy to External Drive - future usage. Now, restart again in Safe Mode - then launch the Installer.

Bob Owen wrote:

#1 - As I have had a Mac since 1988, I have never had this kind of problem to update the OS.

#2 - I have also experienced a host of slow startups, and seemingly unnecessary reboots, since installing the first version of Big Sur. I was hoping that the latest update would solve these problems.

#1:

I agree. But remember back in those days Macs could run on must 128 MBs. Systems were a lot simpler then. Today they are extremely complex what with the security concerns and the full installer is around 12.5 GB in size.

I have a 2017 iMac and have found that the following has been more reliable in applying the latest Big Sur updates that going thru the System/Softrware Update preference pane:

1 - boot into Safe Mode according to Start up your Mac in safe mode - Apple Support.

NOTE: Safe Mode boot can take up to 10 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

2 - go to the App Store, search for Big Sur and download the full sized installer.

3 - install while still in the Safe Mode.

#2:

That can be an indication of incompatible 3rd party software. Download and run Etrecheck. Etrecheck is a diagnostic tool that was developed by one of the most respected users here in the ASC and recommended by Apple Support  to provide a snapshot of the system and help identify the more obvious culprits that can adversely affect a Mac's performance.

IMPORTANT:

Before running Etrecheck assign Full Disk Access to Etrecheck in the Etrecheck's Privacy preference pane so that it can get additional information from the Console and log files for the report:

Also click and read the About info to further permit full disk access.

Copy the report

and use the Additional Text button to include the report in your reply.

Then we can examine the report and see if we can determine what might be causing the problem.

Of course there are recommendations based on numerous similar cases in these forums and you can try them or not.

First, there is no reason to ever install or run any 3rd party "cleaning", "optimizing", "speed-up", anti-virus, VPN or security apps on your Mac.  This user tip describes what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community.  

There are no known viruses, i.e. self propagating, for Macs.  There are, however, adware and malware which require the user to install although unwittingly most of the time thru sneaky links, etc.   

Anti Virus developers try to group all types as viruses into their ad campaigns of fear.  They do a poor job of the detecting and isolating the adware and malware.  Since there are no viruses these apps use up a lot of system resources searching for what is non-existent and adversely affect system and app performance.

There is one app, Malwarebytes, which was developed by a long time contributor to these forums and a highly respected member of the computer security community, that is desshoigned solely to seek out adware and known malware and remove it.  The free version is more than adequate for most users.  

Also, here's some food for thought: Uuervers, they are useless from a privacy standpoint: Public VPN's are anything but private.  

That being said uninstall both Avira Security and TunnelBear according to the developer's instructions. When done you can check to see if you've removed all of the supporting files by downloading and running the shareware app Find Any File to search for any files with the application's or the developer's name in the file name.  For the software mentioned you'd do the following search(es): 

1 - Name contains avira

2 - Name contains tunneler

Any files that are found can be dragged from the search results window to the Desktop or Trash bin in the Dock for deletion.

FAF can search areas that Spotlight can't like invisible folders, system folders and packages.  

If you find that you can move any found files too the trash because they are in use boot into Safe Mode and run Find Any File from there.

Also go to the Clean Up section of the report and remove the orphaned files listed.

Same question - Additional info - Get Error message "Download fails - An error occurred while downloading the selected updates. Please check your internet connection and try again." This has been occurring for days.

I get the same error message. Although not the fastest internet connection out there, I have 100MBps service. My iMac is hardwired through a Gigabit LAN to my router.

With all due respect to P. Phillips, the suggestions are a bit too cumbersome for me to perform an OS update. As I have had a Mac since 1988, I have never had this kind of problem to update the OS.

I wonder if there is something to do with the fact that I have an Intel machine and the update seems to be all about the new processor capabilities.

Bottom line - I don't believe it has anything to do with my LAN/WAN connection.

I have also experienced a host of slow startups, and seemingly unnecessary reboots, since installing the first version of Big Sur. I was hoping that the latest update would solve these problems.

Agree with the Complicated method is just that - thought it has worked in the past for both myself and several others.

Have done the Safe Boot and Apple Store route and downloaded the Full Version on top of 11.2.3 - successfully. Done the Safe Boot and Software Update route - also successfully. So. there various methods all arriving at the same point - Successful Installation.

There exist yet another route and that involves creating a Bootable Installer and use it to update or upgrade the OS.

All is predicated on due diligence on the part of the user to insure all the dots are doted and all the tees are crossed.

I deleted both Avira (antivirus) and TunnelBear (VPN) and used FAF to search for and delete any related files. I did a scan with Malwarebytes and found nothing. Also removed orphaned files as you suggested.

After rebooting, I tried the install for Big Sur 11.3 ... and it worked!

It got past the previous stall point where the Error message "Download fails - An error occurred while downloading the selected updates. Please check your internet connection and try again." occurred.

Thank you for the help, and the education links regarding VPN services and antivirus s/w.

Here is my report as you suggested. Seems to indicate major issues! I did turn off Time Machine on purpose.

If doing over Wifi which is iffy at best - remove all other devices using the Wifi and be as close the Router as possible plus perform from Safe Mode.

It simply does not work. I tried all the above. Very frustrating.