Cant reinstall macOS from Recovery Mode

[Bhu]

Hi im on macOS High Sierra with an iMac 27" late 2009

it has been fine but from out of the blue it is constantly laggy especially iTunes with the little spinning wheel all the time. It makes no sense as theres been no updates or nothing installed. Its very frustrating.

Its a 2.66 GHz intel core i5 processor
Its got 32GB 1067 Mhz DDR3 rom
and the ram is not even half full with over 650GB free space

I tried to do a fresh install and get "can't connect to server error"

I tried several times to connect and every time same error

I checked the network connectivity both wifi and ethernet were good.

Any advice much appreciated.

 

[TonyAguila]

See if you can reboot in Safe Mode (power up and immediately hold down the Shift key). Double check to see if your are connected to the internet. Launch Terminal (/Applications/Utilities/Terminal.app). At the prompt, enter the code:

softwareupdate --list-full-installers

after which you should get something like this:

listing all of the updates available to your particular Mac. In this example, it shows all the files that apply to my Mac. Top on the list for your iMac should be macOS 10.13.6 (17G65), or something newer. Anyway determine the version number and enter this line in Terminal:

sudo softwareupdate --fetch-full-installer --full-installer-version 10.13.6

or the higher version shown on the list. Press return and enter your admin password. The download should start and when done, the installer file should be inside your Applications folder. When the download is done, try to save a copy of the file to another location for future use. Then launch the installer file in the Applications folder, cross your fingers, and wait for the installation to finish.

 

[JonathonPerry]

It might be worth resetting your PRAM/NVRAM and SMC, which can sometimes clear up weird performance issues on older Macs. For the server error during the fresh install, you might want to try downloading the installer from a different source or use a USB installer if you have one. Also, make sure your date and time settings are correct, as this can sometimes cause connection issues during installation.

 

[TonyAguila]

As long as you are connected to the internet, a new installation of macOS should automatically set the correct time to your location. The main thing to keep in mind is that once you reset parameter RAM (PRAM), if your system drive is an SSD and formatted as APFS, you must re-enable TRIM. This is vital for your SSD’s health. I find that the majority of my clients’ Macs do not have TRIM enabled, and File Vault turned off, and I have to instruct them on how to turn them on.

 

[JonathonPerry]

Sometimes these things can happen out of the blue, even without updates or changes. Have you checked if there's any background process consuming resources? Sometimes apps or services running in the background can cause slowdowns. Also, have you tried restarting your router or modem? Sometimes network issues can affect connectivity during installations.

 

[TonyAguila]

Sometimes these things can happen out of the blue, even without updates or changes. Have you checked if there's any background process consuming resources? Sometimes apps or services running in the background can cause slowdowns. Also, have you tried restarting your router or modem? Sometimes network issues can affect connectivity during installations.

In addition, with thousands of files being opened, read, sometimes altered, and so forth, these switches are bound to produce corruption in those files in the long run. It’s a good practice to keep a fresh up-to-date copy of your macOS installer and just rerun the installation, ideally from a safe boot, in order to refresh your system files.