Mac OS X will not boot (Flashing ?)

December 2016

Intro


Upon booting MacOSX all I get is a folder decorated with a flashing question mark instead of the usual Apple logo? What can be done?

This error indicates that your MAC is unable to load the operating system.
  • There are several explanation for this problem:
  • The operating system is not actually installed
  • Wrongly selected boot disk
  • Corrupted disk
  • Disk full





Operating system not installed

  • Use the MacOSX installation CD/DVD to remedy this.
  • Otherwise it's better to check out of the possible scenarios before sending your MAC in for repair

Change the startup disk

Without installation CD/DVD


Press the <alt> key a startup and select your disk.

Using the installation CD/DVD

  • Insert the media into the drive, press the <C> key at startup to boot from the DVD, choose your language, but do go to the installation section.
  • Search the top menu, Utilities> Startup Disk, select your hard drive, click Restart.
  • If your system boots check in System Preferences (Apple menu)/Start if the disk selected is indeed the right one (to boot your OS).

Corrupted disk

Using the installation CD/DVD

  • Insert the media into the drive, press the <C> key at startup to boot from the DVD, choose your language, but do go to the installation section.
  • Search the top menu, Utilities> Disk Utility, select your hard disk check/repair permissions (if necessary), verify/repair the disk.
  • Quit the disk utility tool and restart your MAC.

Disk full


If the boot disk is correctly configured and there's no error detected, your hard drive may just be full.
In this case you must make space and everything will be fine.

The manipulation is acheived in command line.

Without installation CD/DVD


You can try to start holding down the Apple + s keys and click (single-mode boot, it this works then you shall have the UNIX console, as root)

Using the installation CD/DVD


Insert the media into the drive, press the <C> key at startup to boot from the DVD, choose your language, but do go to the installation section.
  • Search the top menu, Utilities> Disk Utility, select your hard drive, and click 'Mount Volume', quit the Disk Utility.
  • Search the top menu, Utilities> Terminal, a bash terminal opens with a root session.

Information Retrieval


The df command will tell you the amount of available space on the mounted volume:
$ df -h 
Filesystem                Size   Used  Avail Capacity  Mounted on 
/dev/disk0s2               90G    82G   7.9G    91%    / 
devfs                      98K    98K     0B   100%    /dev 
fdesc                     1.0K   1.0K     0B   100%    /dev 
<volfs>                   512K   512K     0B   100%    /.vol 
automount -nsl [170]        0B     0B     0B   100%    /Network 
automount -fstab [174]      0B     0B     0B   100%    /automount/Servers 
automount -static [174]     0B     0B     0B   100%    /automount/static
  • If you start up your MAC with the installation DVD/CD, the mount point of the hard drive will be like that:
    • /Volumes/DISK_NAME
  • The du command is not available by default, but is normally present on your hard drive, type the following command:
    • alias du='/Volumes/DISK_NAME/usr/bin/du'
  • Then use the command:
    • du -sch directory_name


From there you will know the size occupied by a directory.
Search in the following directories (in most cases):
  • User (/Volumes/DISK_NAME/Users/login/)
  • log files (/Volumes/DISK_NAME/var/log)



Once cleaning is done, try to restart your MAC by closing the terminal, then via Utilities> Startup Disk

Note that: In the case you are performing these manipulation using a terminal launched from CD/DVD installation, all the commands are usually available as long as:
  • The hard drive is mounted
  • The following directories are in the path
    • /Volumes/DISK_NAME/bin
    • /Volumes/DISK_NAME/usr/bin
    • /Volumes/DISK_NAME/sbin
    • /Volumes/DISK_NAME/usr/sbin


The commands available on the CD can hanlde these issues, but having access to all the usual command is better!

Related :

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