Can't log in to El Capitan after Mavericks upgrade

[WalnutSpice]

On my early 2009 Macbook (white, not pro) I've been running Mavericks and Leopard 10.5 (for PowerPC apps). I decided to finally upgrade to El Capitan. On Mavericks I had no password. Now that El Capitan is installed, It goes to the log in screen and tells me to enter a password. I don't have one. I put in nothing, says its wrong. I put in my itunes password, says its wrong. Booted into the recovery partition, it freezes. I boot into Leopard, it no longer boots fully after upgrading the other partition to 10.11.
I have no idea what to do

--edit--
Leopard 10.5.8 decided to boot up after three more tries. Running disk permissions / fixing. Going to create a 10.11 USB with disk utility. Hopefully you can still change a password through that. If not, I'm just screwed I guess. Thanks Apple.

Note to people reading this, Don't upgrade to El Capitan without a user password. Better yet, don't upgrade past 10.9 at all. Hell, stay on Snow Leopard.

 

[DeltaMac]

As you may now have a password set - try to change the password, you don't need that "unknown" password.
Here's a way to do that...
boot to your Recovery system (Restart, holding Command-R)
Go the terminal from the menus, then type in the command line

resetpassword

(no spaces!)
The reset password app will launch.

Select your hard drive, and select your user account name from the dropdown.
Type in your password (you can't remove password completely, but you can make it easy for YOU to remember)
Type it again to verify, then click Save. Quit the terminal, and choose restart from the menu.
You will boot to your login screen. You should now be able to successfully login with your new password.

 

[garirry]

I would also like to add that after you've done so, you can go to system preferences and remove the password if you're sure you don't want it (I think you have to go to Change Password, enter your old password, and leave everything else blank).

 

[WalnutSpice]

As you may now have a password set - try to change the password, you don't need that "unknown" password.
Here's a way to do that...
boot to your Recovery system (Restart, holding Command-R)
Go the terminal from the menus, then type in the command line

resetpassword

(no spaces!)
The reset password app will launch.

Select your hard drive, and select your user account name from the dropdown.
Type in your password (you can't remove password completely, but you can make it easy for YOU to remember)
Type it again to verify, then click Save. Quit the terminal, and choose restart from the menu.
You will boot to your login screen. You should now be able to successfully login with your new password.

Thanks, but yeah I figured it out. I originally tried to do it the way I used to do back on OS X Tiger but soon found that new method online.
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I would also like to add that after you've done so, you can go to system preferences and remove the password if you're sure you don't want it (I think you have to go to Change Password, enter your old password, and leave everything else blank).

The problem was I didn't have any password, which is okay on Mavericks. But you have to have a password on El Capitan. So when I upgraded and I had a user account that didn't have a password, 10.11 didn't understand what to do with it.

 

[garirry]

The problem was I didn't have any password, which is okay on Mavericks. But you have to have a password on El Capitan. So when I upgraded and I had a user account that didn't have a password, 10.11 didn't understand what to do with it.

From my 30-second research, it seems that if you use iCloud to log in, have FireVault or KeyChain active, the password is required.