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Odd OS X failure mode

 
 
Lawrence D'Oliveiro
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      08-13-2007
I have a client who's reported an odd problem on one of his Macs running OS
X. Apparently instead of booting up to the normal GUI, it's only presenting
a Darwin console login screen.

I don't have much experience of OS X, but I've never heard of Macs doing
this sort of thing. With the older MacOS, if you didn't get the GUI, it was
because the machine was failing to boot altogether.

If this was a Linux box, I'd say the X server failed to start, possibly
because of a driver or configuration problem, or (in the couple of cases
where it actually happened to my clients) the partition containing the /tmp
directory getting full. But since OS X doesn't (normally) run an X server,
I don't know if similar considerations apply.

Thoughts, anyone?
 
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Hank
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      08-13-2007
>
> Thoughts, anyone?


Replace it with a windows machine.

 
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David Empson
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      08-14-2007
Lawrence D'Oliveiro <(E-Mail Removed)_zealand> wrote:

> I have a client who's reported an odd problem on one of his Macs running OS
> X. Apparently instead of booting up to the normal GUI, it's only presenting
> a Darwin console login screen.


Does the startup sequence look normal prior to this point?

It should do the startup chime, show a grey background with dark grey
Apple logo, spinning activity indicator, then go to a blue screen with
startup progress information (sometimes skipped if the computer is fast
enough) before getting to the login prompt.

There is a method of deliberately getting a console login screen if you
type in the right incantantion at the login prompt (assuming you have it
set to ask for a username and password, rather than a clickable list of
users, or automatically logging on as a particular user).

There is also a "single user" mode which you can get to by holding down
the right key combination at startup. This gives you a root shell and
doesn't ask for any passwords. (There are additional security mechanisms
to prevent access to this without a password, if you are worried about
physical security of the computer.)

It doesn't sound like single user mode, so my guess is that something is
causing it to go straight to the console login prompt.

If I do this deliberately (by entering ">console" as the user name on
the GUI login screen), I get a black screen with white text which says:

Darwin/BSD (name-of-computer.local) (console)

login:

At this point, if I enter an incorrect user name and password once, it
drops me back out to the GUI login window. If I enter a correct user
name and password it gives me a shell prompt.

Have they tried entering their user name and password? If it at least
gets a shell prompt there is a chance of being able to investigate
further and fix it.

> I don't have much experience of OS X, but I've never heard of Macs doing
> this sort of thing.


Me either, and I do Mac technical support for a reasonable number of
people.

> With the older MacOS, if you didn't get the GUI, it was
> because the machine was failing to boot altogether.
>
> If this was a Linux box, I'd say the X server failed to start, possibly
> because of a driver or configuration problem, or (in the couple of cases
> where it actually happened to my clients) the partition containing the /tmp
> directory getting full. But since OS X doesn't (normally) run an X server,
> I don't know if similar considerations apply.
>
> Thoughts, anyone?


A possibly useful trick would be to start up the comptuer in Verbose
mode, which will remain in text mode for the startup sequence (until it
gets to the login window or prompt). This might reveal some clues about
the problem, e.g. it might show an error message.

To start up in verbose mode, hold down the Command-V key combination
(Command is key with the Apple and Propellor symbols, to the left of the
space bar) immediately after the startup chime, and keep holding them
down until you get the text screen showing the details of the boot
sequence.

Most of it is gobbledigook to the average user but it should be
intelligible to someone familar with Unix-a-like systems.


I suspect the problem will be a corrupted preference file for
loginwindow, or some component of the system has become damaged,
resulting in it not being able to launch the loginwindow application,
forcing it to revert to a console login.

It might also be a fallback feature due to the automatic login account
being damaged in some way which prevents login from occurring.

This might be fixable by locating the damaged file, but it may be easier
to do a system reinstall (using the "Archive and Install" method, which
preserves user accounts and as much third party software as possible).

I suggest you e-mail me directly for further discussion.
--
David Empson
http://www.velocityreviews.com/forums/(E-Mail Removed)
 
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Lawrence D'Oliveiro
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      08-14-2007
In message <1i2u6tq.1b2id0l104oabvN%(E-Mail Removed)>, David Empson
wrote:

[lots of detailed advice]

Thanks for that info. I was with the client today, discussing other things,
and he didn't mention the problem, so he must have got it resolved, perhaps
by contacting his usual OS X support people.

I must admit I was amazed at your description of all those cryptic key
combinations to get into single-user mode, verbose mode and so on. It seems
so much simpler on a Linux system.
 
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whoisthis
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      08-14-2007
In article <f9qpd6$9p6$(E-Mail Removed)>,
Lawrence D'Oliveiro <(E-Mail Removed)_zealand> wrote:

> I have a client who's reported an odd problem on one of his Macs running OS
> X. Apparently instead of booting up to the normal GUI, it's only presenting
> a Darwin console login screen.
>
> I don't have much experience of OS X, but I've never heard of Macs doing
> this sort of thing. With the older MacOS, if you didn't get the GUI, it was
> because the machine was failing to boot altogether.
>
> If this was a Linux box, I'd say the X server failed to start, possibly
> because of a driver or configuration problem, or (in the couple of cases
> where it actually happened to my clients) the partition containing the /tmp
> directory getting full. But since OS X doesn't (normally) run an X server,
> I don't know if similar considerations apply.
>
> Thoughts, anyone?


Probably has gone into it open-firmware mode.
You can get this by holding down Command-option-o-f

When you are in this mode type
reset-nvram
reset-all

This resets the pram and reboots the machine, all should be good again.
 
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whoisthis
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Posts: n/a
 
      08-14-2007
In article <(E-Mail Removed). com>,
Hank <(E-Mail Removed)> wrote:

> >
> > Thoughts, anyone?

>
> Replace it with a windows machine.


See.... when you don't specify INTELLIGENT thoughts, all sorts of idiots
come out of the woodwork thinking they are funny.
 
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Bobs
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      08-14-2007
Lawrence D'Oliveiro wrote:
> I have a client who's reported an odd problem on one of his Macs running OS
> X. Apparently instead of booting up to the normal GUI, it's only presenting
> a Darwin console login screen.
>
> I don't have much experience of OS X, but I've never heard of Macs doing
> this sort of thing. With the older MacOS, if you didn't get the GUI, it was
> because the machine was failing to boot altogether.
>
> If this was a Linux box, I'd say the X server failed to start, possibly
> because of a driver or configuration problem, or (in the couple of cases
> where it actually happened to my clients) the partition containing the /tmp
> directory getting full. But since OS X doesn't (normally) run an X server,
> I don't know if similar considerations apply.
>
> Thoughts, anyone?



Had a Windows 2000 box running for 7 years with no problems and not one
crash. Buy a real OS.

Thanks for coming.

 
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David Empson
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      08-14-2007
Lawrence D'Oliveiro <(E-Mail Removed)_zealand> wrote:

> I must admit I was amazed at your description of all those cryptic key
> combinations to get into single-user mode, verbose mode and so on.


That's nothing. There are a lot more of them.

Mostly to do with overriding the normal startup disk and booting from
somewhere else, or going into a special mode.

My favourite is the 'T' key, which puts a Mac into Firewire target mode.
It then acts like a Firewire hard drive which can be connected to
another computer. Great for copying lots of files, or to repair the
internal hard drive, or to boot one computer from another's internal
drive, or to migrate the entire system over to a new computer (which Mac
OS X offers to do during the initial setup of a new computer).

> It seems so much simpler on a Linux system.


I expect most Linux systems would normally start up in the equivalent of
Mac OS X's verbose mode. (My IPCop installation spits out pages of
status messages on the console while starting up.)

The Mac's policy has always been to have the normal startup sequence a
clean and largely icon or picture-based experience, avoiding excessive
use of text and technical terms, except if something goes wrong.

--
David Empson
(E-Mail Removed)
 
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Lawrence D'Oliveiro
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Posts: n/a
 
      08-15-2007
In message <1i2v3i5.bicjda7f15b1N%(E-Mail Removed)>, David Empson
wrote:

> Lawrence D'Oliveiro <(E-Mail Removed)_zealand> wrote:
>
>> I must admit I was amazed at your description of all those cryptic key
>> combinations to get into single-user mode, verbose mode and so on.

>
> That's nothing. There are a lot more of them.
>
> Mostly to do with overriding the normal startup disk and booting from
> somewhere else, or going into a special mode.
>
> My favourite is the 'T' key, which puts a Mac into Firewire target mode.
> It then acts like a Firewire hard drive which can be connected to
> another computer.


That feature is quite old on Macs. I think it might date back to some of the
earliest PowerBook models from 1992. Only in those days there was no
FireWire, but Macs had SCSI ports then. So it was called "SCSI disk mode",
or maybe "SCSI target mode". But it was still the "T" key you held down.

But really, why is this feature necessary? It only seems needed if the OS
doesn't let you access certain files via a network while it's running. That
was true of old MacOS, I'm surprised it's still true of OS X today.

> Great for copying lots of files, or to repair the
> internal hard drive, or to boot one computer from another's internal
> drive, or to migrate the entire system over to a new computer (which Mac
> OS X offers to do during the initial setup of a new computer).


All of which you can do on a Linux system while it's still running.

>> It seems so much simpler on a Linux system.

>
> I expect most Linux systems would normally start up in the equivalent of
> Mac OS X's verbose mode. (My IPCop installation spits out pages of
> status messages on the console while starting up.)


Some distros, yes. Others put up a pretty graphical display, but there's
usually small print at the bottom saying "Press Esc for details" or
something like that.

> The Mac's policy has always been to have the normal startup sequence a
> clean and largely icon or picture-based experience, avoiding excessive
> use of text and technical terms, except if something goes wrong.


The normal Linux policy is to first present the bootloader menu. That has a
default option that will be selected if you don't hit a key within the
timeout interval (e.g. 8 seconds). For instance, selecting single-user mode
is as simple as typing the word "single", which gets appended to the kernel
command line. I think that's better than remembering cryptic keystrokes,
don't you think so?
 
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David Empson
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Posts: n/a
 
      08-15-2007
Lawrence D'Oliveiro <(E-Mail Removed)_zealand> wrote:

> In message <1i2v3i5.bicjda7f15b1N%(E-Mail Removed)>, David Empson
> wrote:
>
> > My favourite is the 'T' key, which puts a Mac into Firewire target mode.
> > It then acts like a Firewire hard drive which can be connected to
> > another computer.

>
> That feature is quite old on Macs. I think it might date back to some of the
> earliest PowerBook models from 1992. Only in those days there was no
> FireWire, but Macs had SCSI ports then. So it was called "SCSI disk mode",
> or maybe "SCSI target mode". But it was still the "T" key you held down.


Old PowerBook models get into SCSI target mode by using a special SCSI
adapter. The ones I've seen have a switch on them which selects between
normal operation and target mode.

The 'T' key was introduced with Firewire Target Mode (early 2000).

> But really, why is this feature necessary? It only seems needed if the OS
> doesn't let you access certain files via a network while it's running. That
> was true of old MacOS, I'm surprised it's still true of OS X today.


Mac OS X follows a standard Unix privileges model. If you log into a
computer via the network, your access to files is determined by
ownership and access privileges, according to who you log in as.

The standard file sharing protocol (AFP) doesn't provide any way to
bypass the privilege system.

You can get unrestricted access if you are able to ssh into the Mac as
an administrative user then use sudo to get root privileges. You can
only do this if the computer has been set up to allow remote login
(disabled by default).

The average Mac user doesn't want to go fiddling around with command
line tools, so doing an "unrestricted file copy" via a network is beyond
the capabilities of most Mac users.

There might be software which makes this task easier, but Firewire
target mode is signficantly easier and makes more sense to the average
user.

Setting up network file transfers requires enabling sharing on at least
one computer, making sure your TCP/IP settings are compatible, and
knowing at least one user account and password on the computer.

Firewire target mode requires no special knowledge other than how to use
an external hard drive, where to plug in the Firewire cable, and when to
press the 'T' key.

> > Great for copying lots of files, or to repair the
> > internal hard drive, or to boot one computer from another's internal
> > drive, or to migrate the entire system over to a new computer (which Mac
> > OS X offers to do during the initial setup of a new computer).

>
> All of which you can do on a Linux system while it's still running.


Yes, if you know how or have the right tools. The same applies to Mac OS
X, but most Mac users don't have the technical skills of the average
Linux expert.

> > The Mac's policy has always been to have the normal startup sequence a
> > clean and largely icon or picture-based experience, avoiding excessive
> > use of text and technical terms, except if something goes wrong.

>
> The normal Linux policy is to first present the bootloader menu. That has a
> default option that will be selected if you don't hit a key within the
> timeout interval (e.g. 8 seconds). For instance, selecting single-user mode
> is as simple as typing the word "single", which gets appended to the kernel
> command line. I think that's better than remembering cryptic keystrokes,
> don't you think so?


Ignoring the issue of people wanting to use multiple operating systems
for a moment:

The average Mac user with a current Mac model has a single hard drive
with a single partition, and a single installation of Mac OS X on it.
The only thing they do at startup is boot the same operating system.
(They might have additional drives for backups or extra data storage,
but only a few would ever boot from them.)

They might boot from CD once in a blue moon, so if they know about the
'C' key it will save them a little time. (There is a GUI tool to select
the startup volume if they don't know the shortcut.)

Why present options to a non-technical person who will never use them,
and why waste time waiting for an answer to a question which will always
be the same?

Things are slightly more complex if you want to install more than one
operating system. You might need to know about things like partitioning
the hard drive. Someone with an older Mac might have both Mac OS 9 and
Mac OS X on it. Linux is an option on most Macs, and booting directly
into Windows is an option on current models (via Boot Camp).

Changing the startup volume is normally done with a GUI tool (on Mac OS
X and Mac OS 9; probably a command line tool on Linux and a special
application on Windows). Knowing about the Option key will let you pick
a volume (and its corresponding OS) when you start up.

That's two startup keys which might be useful to slightly more advanced
Mac users.

The other special startup keys are used so rarely that the average Mac
user doesn't need to know about them. If they do, they are documented in
the online help and in the troubleshooting section of the manual.

They are more commonly used when diagnosing or solving problems, and
that's when someone with more experience (who knows about these details)
gets called in. Problems that require anything more complex than booting
from CD are extremely rare. For example, I've been doing Mac OS X tech
support for about six years on dozens of computers, and I can only think
of two occasions where I needed single user mode, though I've sometimes
used it just because it was the quickest way to solve a problem.

--
David Empson
(E-Mail Removed)
 
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