Macbook frozen on installation log

Press and hold down the Power button until the computer shuts down. After 30 seconds restart the computer. If you are unable to get the computer to start and complete the installation then try the following:

Reinstall El Capitan or Later Without Erasing Drive

Please be sure you back up.

1. Restart the computer. At or before the chime hold down the Command and R keys until the Utility Menu appears.
2. Select Disk Utility and click on the Continue button.
3. Select the indented (usually, Macintosh HD) volume entry from the side list.
4. Click on the First Aid icon in the toolbar. Wait until the Done button activates, then click on it.
5. Quit Disk Utility and return to the Utility Menu.
6. Select Reinstall OS X and click on the Continue button.

Also, see this User Tip: Basic Steps for Upgrading OS X.