Yosemite freeze at boot - no safe boot + I/O error Yesterday everything was fine but today my macbook freeze/stuck during the boot.  

I've done this:  


check + repair permission (nothing changed)
check + repair disk (nothing changed)
tried safemode (doesn't boot)
resetting pram with cmd+opt+p+r (nothing changed)
boot in verbose mode, shift+cmd+v and after "waiting for DSMOS" appear disk0s2: I/O error. (now 6 times, but it will continue I think )
tried to use fsck in single user mode and it says that the disk is ok
tried to reinstall the OS (nothing changed )




Any idea how to solve it?
I/O problems are a good indicator that your drive is past its best. Replace the drive or do the following...

Back up everything of value via Target Disk Mode (if possible) then boot your MacBook from a USB or DVD installer. Run Disk Utility, selecting the secure erase/zero fill option and wipe your drive.

This will issue an ATA secure erase command that will fill every allocation block with a zero, automatically mapping out any bad blocks/sectors that will be causing your I/O problem. This is the modern equivalent of the old low-level format, and while there is some debate on the subject I use this method regularly and it works well - assuming the drive isn't riddled with bad blocks.

All FSCK does is check the file structure, it doesn't scan the drive surface to determine if the drive has any damaged sectors. Even the drive's internal SMART diagnostics may indicate all is well when in actual fact the drive is on its way out.