How does Mac OS X decide which volumes to mount at boot?

[ajbrehm]

I have four disks in my Mac Pro. The boot disk and two others mount when OS X starts but the fourth one does not. I can mount it in Disk Utility and it appears to be all right.

How can I tell Mac OS X to mount it?

How does Mac OS X decide which volumes to mount at boot? Where is that done or configured?

 

[Heynonny]

How does Mac OS X decide which volumes to mount at boot? Where is that done or configured?

You say "in" but if the fourth drive is actually an external then the Finder Preferences must have "external disks" checked under"Show these items on the desktop"

 

[ajbrehm]

You say "in" but if the fourth drive is actually an external then the Finder Preferences must have "external disks" checked under"Show these items on the desktop"

No, all four drives are internal.

Also, this is about mounting the drives, not about displaying them on the desktop (or the Finder).

 

[varunsanthanam]

I've wondered about this for some time now. Perhaps its a setting from disk utility? No idea... I could see it being something like a checkbox for "mount this disk on startup"

Sorry I couldn't be more helpful!

Any other answers are appreciated, I am having a similar dilemma with an internal SSD and an internal HDD. Neither of them are the boot volume, but the SSD mounts on startup while the HDD does not.

 

[ajbrehm]

I've wondered about this for some time now. Perhaps its a setting from disk utility? No idea... I could see it being something like a checkbox for "mount this disk on startup"

Sorry I couldn't be more helpful!

Any other answers are appreciated, I am having a similar dilemma with an internal SSD and an internal HDD. Neither of them are the boot volume, but the SSD mounts on startup while the HDD does not.

I have also asked this question at the Apple Stackexchange but all I got was the Finder display icon thing and a nasty discussion with some angry guy.

I will make sure to post here when I get an answer elsewhere. In the mean time, everybody else reading here, please help us!

 

[ScoobyMcDoo]

You might try adding an entry to /etc/fstab. You can find documentation by opening a terminal and typing "man fstab"

 

[ajbrehm]

You might try adding an entry to /etc/fstab. You can find documentation by opening a terminal and typing "man fstab"

Actually, that might solve ShadowMac's problem. I found a site that explains this a bit (although for people who want to stop a drive from mounting):

http://hints.macworld.com/article.php?story=20060930150059172

Or this might:

http://hints.macworld.com/article.php?story=20031103155828117

But it does not answer my question. I need to know how Mac OS X decides which drives to automount at boot. Mac OS X obviously doesn't rely on fstab to make that decision.

Thanks.

 

[NeilSmithline]

Thank you ScoobyMcDoo

You might try adding an entry to /etc/fstab. You can find documentation by opening a terminal and typing "man fstab"

I didn't know that MacOSX used fstabs. It has that fstab.hd file that says its deprecated but no fstab by default. Once you pointed me to the man page, and after hitting myself in the forehead for having not looked at it before, it only took me 10 minutes or so to figure it out.

I still don't know the answer the original question about how MacOSX determines what to mount where. But I do know how to work around it.

I like to have my Applications directory on a separate partition. That makes life easier when I FUBAR my / filesystem as I don't have to install all my apps again. I've tried symlinks and such but whatever I try never quite works right. But now my fstab reads:

/dev/disk0s5 /Volumes/Applications hfs noauto
/dev/disk0s5 /Applications hfs union 0 2

And life is good.

The first line tells MacOSX to not automatically mount disk0s5 to /Volumes. The second line tells it where I want it mounted. Being it is a rather important directory for the OS to work, I use the "union" option so that the original files are still accessible from /Applications. Big win should my mount fail.

Thanks all!

Neil
http://www.neilsmithline.com

PS: In case you're wondering, I routinely FUBAR my / partition. I find that my computer always *needs* just one more tweak and sometimes that is a tweak too far

 

[larkost]

By default MacOS X mounts everything that it can. So there is something that is keeping your final disk from mounting. My guess is that there is probably something in syslog that will tell you what it is thinking. There might be something in /var/log/system.log, but I would go the full route and use this right after you boot:

sudo syslog -B

That will get you all of the messages since the machine booted. Usually there is a bit of extra debug spew in there that does not make it into any of the text log files.

 

[sososowhat]

Tinker Tool seems to be the way to go. Under 10.8.2 I edited /etc/fstab as described to prevent mounting & it didn't seem to work. Tinker tool launched & thought the mount was prevented, but it wasn't. I deleted that line in TinkerTool, then re-added it using the tool, and voila, my old 750Gig HD (in the optical bay of my MBP doesn't mount when I boot) and I silent and still off the SSD. Happy camper. Thanks for the pointer.

 

[rthpjm]

Actually, that might solve ShadowMac's problem. I
But it does not answer my question. I need to know how Mac OS X decides which drives to automount at boot. Mac OS X obviously doesn't rely on fstab to make that decision.

Thanks.

I know this is an old thread, but the OP's question was not really answered (or it was, but without understanding why!).

It is diskarbitrationd that manages the system view of mounting disks. Here is the man page description:

diskarbitrationd listens for connections from clients, notifies clients of the appearance of disks and filesystems, and governs the mounting of filesystems and the claiming of disks amongst clients.

More importantly the man page explicitly states that diskarbitrationd reads the /etc/fstab file:

The file /etc/fstab is consulted for user-defined mount points, indexed by filesystem, in the mount point determination for a filesystem.

Therefore the answers given for using /etc/fstab are correct, and this is the reason why.

You can read the manual page for diskarbitrationd in the Terminal:

man diskarbitrationd

RTH