Q: My MacBook Pro will not boot, but I can mount its disk. How do I extract the system profile?

The system profile is not stored on the drive. When needed, it is computed in real-time.

what are you looking for, exactly?

The gray screen on startup may can be a symptom of troubles, such as failed hard drive.

Or just some confusion about what to do next, on the part of a troubled Mac.

Sometimes, a gray screen on startup can be alleviated by resetting NVRAM (PRAM)

1. Power down your Mac. Press and hold the power button to force shutdown if necessary.
2. Power up your Mac and press the “Command-Option-P-R” keys before the gray screen appears.
3. Press the keys until your Mac restarts and you hear the startup sound twice.
4. Release the “Command-Option-P-R” keys.

• Try safe mode if your Mac doesn't finish starting up - Apple Support

Sometimes, trying to start in Safe boot mode, with shift key held down immediately

after the start tone is heard; and wait to see if the progress bar appears in bottom

of display. If it does, you should be asked for Admin Password, to get into SafeBoot.

A general overview of different screens -- no longer covers the 'gray screen' -- even indirectly:

• About the screens you see when your Mac starts up - Apple Support

Non-running information about your computer can be found by use of serial number

to identify the exact build model. Some ideas follow:

You can find details + other information about your MacBook Pro can be obtained

by locating the product serial number; from case, original box, or sales invoice.

In general, there is this Apple support article to help identify any MacBook Pro:

• How to identify MacBook Pro models - Apple Support

With that number you could learn the original as-shipped configuration, build

date and month, plus the system and other hardware specs when it was new.

A lookup service such as this, can help in this regard; for your own information.

So to say, do not post your serial number in this ASC thread, is about security.

• Mac Serial Number Info - Lookup your Apple Serial Number:

https://www.powerbookmedic.com/identify-mac-serial.php

If you have a backup clone of the computer, you could see if it may start from

the boot-able full system copy (usually on external HDD, or USB Flash.)

If the hard drive has failed, then there are methods to attempt to restore; helps

to have a few backups such as Time Machine, and additional external archives.

For some ideas that aren't along the line of your question, (only in circumstance)

see - Apple OS X & Time Machine Tips: http://www.pondini.org/OSX/Home.html

• Have you tried booting in OS X Recovery? If the recovery partition is intact, you

may be able to get a rise out of the machine; you could see if OS X Utilities can

show, where you could then use Disk Utility to see if the hard drive is repairable.

• About OS X Recovery - Apple Support

Since you did not identify the nature of the first problem, hopefully you will get

back to us with more information.

In any event...

Good luck & happy computing!