Funny story: I had to upgrade one of my Mac Minis in a data centre. The poor thing was still running Sierra, and I thought perhaps it was time to upgrade to High Sierra. My software of choice did work fine, but a few other bits did not, plus I didn’t have Dark Mode natively, so I decided to jump to macOS Mojave to see if it worked better.
Turns out after downloading the installer, I was greeted with the dreaded error message you may be familiar with from High Sierra: “Could not reach recovery server”. Rats! Remember I do not have physical access to the machine.
Thankfully Mr. Macintosh had a tip on his website: change the URL in my Mac’s NVRAM on the fly. Turns out the URL the Mac phones home on is a secure location (https), but something appears to be wrong with the certificate so High Sierra doesn’t understand it and as a result perceives a timeout – and hence the error message.
By manually overriding this value with a plain text (http) version of the same URL, the authentication is successful and the upgrade can start. Isn’t that something? What’s even better is that I could do this on a running remote system without having to reboot from a USB stick or boot into recovery mode.
You can read the gory details on Mr. Macintosh’s blog, but essentially what I did was this:
- download and start the Mojave installer from the App Store
- get the error
- open a Terminal window and type the following
sudo IASUCatalogURL="http://swscan.apple.com/content/catalogs/others/index-10.13-10.12-10.11-10.10-10.9-mountainlion-lion-snowleopard-leopard.merged-1.sucatalog"Provide your admin password and run the installer again. Boom! Everybody happy.