while installing the update it ask to restart, before restart it shows error "try again"
although all the apps are closed.
MacBook Air 13", macOS 10.13
Restart in Safe Mode.
Use safe mode to isolate issues with your Mac - Apple Support
Restart in Safe Mode.
Use safe mode to isolate issues with your Mac - Apple Support
First, try restarting in Safe Mode (hold shift at startup) and do the update again in Safe Mode. safe mode does one pass of disk repair as it starts up, so it takes a bout five minutes longer than normal. screen re-draw will be wonky and slow, but ultimately correct.
If this continues to be a problem, you may need a re-Install-in-place. By design, this does not disturb any of your files or any added Applications.
But if your drive is already shaky, it is possible that re-writing the required 350,000 files might force it over the edge into failure. A Trusted backup would be a really good thing to have on hand before you begin.
Error on installation of new update of macOS mojava
