Missing Dock/flashing Desktop OS X

[PaulF]

Running 10.10.2 on a Mac Mini


On my son's account but no others his dock has disappeared and the desktop flashes between the selected wallpaper and black. The "top bar" remains visible so it's not as if the screen connection is lost

[rusky]

does the dock reappear if you move the mouse to the bottom of the screen where the dock should sit?

[Otto]

Check the dock preferences upper left hand corner has he switched on hide dock?

[PaulF]

Thanks, the dock preferences was the first thing that I checked.

[Jaded]

Could be corrupt preferences.

Try deleting the Dock and Finder prefs.

In Finder hold the Alt key down and click go the choose Library and Preferences

You don't have to delete them just drag them onto the desktop. They will be recreated with default settings.

Also check the amount of free space the disk has. Should be an absolute minimum of 10% of total disk size. I've seen this behaviour on a full Mac.

[Otto]

Could you delete his account and give him a new one

[PaulF]

Could be corrupt preferences.

Try deleting the Dock and Finder prefs.

In Finder hold the Alt key down and click go the choose Library and Preferences

You don't have to delete them just drag them onto the desktop. They will be recreated with default settings.

Also check the amount of free space the disk has. Should be an absolute minimum of 10% of total disk size. I've seen this behaviour on a full Mac.

Thanks, just tried that, the Dock appeared for a second of so and then disappeared as soon as the rest of the login had completed.

Space is fine 40%/200+GB

Could you delete his account and give him a new one

That's the nuclear option. I'm reluctant to do that until I find out what caused it in case by copying his data across I recreate the issue

[Otto]

Have you tried a safe restart... holding shift down on re start... often a normal 're start afterwards can iron out minor glitches

[Jaded]

Have you tried an fsck ?

Restart with the cmd and S key held down as the beep sounds, when the text flows up the screen release the S

Follow the instructions to the letter at the bottom of the screen

/sbin/fsck -fy
It may say filesystem has been changed, in which case you can do it again

Then
/sbin/mount -uw/

Type exit to leave

[ian]

I'd try resetting the PRAM and then the SMC. To do the PRAM hold down Cmd-Opt-P-R before the grey screen appears and keep them pressed until it makes the bong noise. It may take several seconds.

To reset the SMC unplug everything (including the power cable) and leave for 30 seconds or so. Plug the power cable and monitor back in and in reboot. Once everything is running, attach any other peripherals.

For video quirk, don't neglect the cables – in my experience video cables and connectors are prone to dodginess.

Other things to try:

(1) a different desktop image etc, the image may be somehow corrupted

(2) restart the dock by opening terminal and typing 'killall Dock' at the prompt. It's case sensitive. You can do the same by selecting the Dock process in Activity Monitor and clicking the big red cross. OSX will restart it.

(3) do the usual verify permissions from Disk Utility

(4) do the disk check Jaded suggests

(5) run a memory check, easiest way to do this is through the Apple Hardware tests - hold Option-D when you start up and follow the instructions.

[PaulF]

Thanks. One further complication: I no longer have a wired keyboard. Is there any way I can do a restart whilst holding down the command key with a Bluetooth keyboard? May be able to find a windows keyboard somewhere at work if I need one.

[Jaded]

It 'should' take the key presses if you do them immediately after the startup chime.

[ian]

Indeed, the bluetooth keyboard should just be there from the moment you start up. Desktop Macs assume wire-free keyboards and mice/trackpads these days.

[PaulF]

Thanks it worked this time. May have been too slow last time!

[Jaded]

If you don't get it happening on another user account then it is likely to be plist files for that user or something they have installed for themselves.
If it happens on another user and the disk repair options don't show anything odd, a more fundamental option is to boot in Recovery mode and reinstall OSX. Command R just after the boot chime. Existing accounts and data should be kept, but a recent back-up or clone is, of course, advisable.
You can use recovery mode to do disk repairs too, as Disk Utility is available from it, but it isn't as deep as doing FSCK