Why won't single user mode recognize /sbin/mount command?

I need help from people who are knowledgable abou these Mac wonders of the world and single user mode.
I'm trying for the life of me to run "memtest" in single user mode and am finding it impossible.
After I boot into single user mode, I get a "Shell>" prompt.
I type in /sbin/fsck/ -y to do some check thing. I then type in /sbin/mount -uw /
Both times I get an error saying that "/sbin/yada yada yada is not recognized as an internal or external command, batch or whatever"
No command work at all. I have no clue what I'm doing and am using instructions from where I got the memtest app. Sure I could just run it from the Terminal but then you're not testing all of the RAM, only the available portion. There's a huge chunck that won't be tested as OSX is using it. I want to do this as I just upgraded RAM to 8G with Crucial and now my MBP is acting very slow and weird.
HELP???? Why does this have to be sooooo hard.

I found the solution to the problem. Somone on a different forum had the same issue at one time. The problem is my use of Refit. When you hold Command-S at start when using refit you go into a single user type mode inside the refit shell. So it is something different.
Instead I needed to let the Mac boot Refit like normal. With the Mac partition highlighted press "F2" and it will display boot options for the Mac partition. One of them is Mac OSX single user mode. Simply select and hit enter and then I enter the correct single user mode and I'm off.
Then everything works like it should. I was my own undoing with my use of Refit.

Similar Messages

Single-user mode: How to mount and access an external USB drive?

My MacBook Pro HD is acting up. Cannot boot normally or into "safe mode". Cannot reinstall OS without wiping out the HD. Need to recover some critical files but DiskUtil First Aid and Restore options cannot successfully complete. Problem traced down to "invalid node structure" which means I either have a hardware problem or my filesystem partition directory structure is corrupted. I need to recover some files that are not backed up (timin issue with my regular backup process).
I can boot into single-user mode, mount the root file system (/sbin/mount -uw /) and can see/navigate the rot filesystem structure via good UNIX command line. Here's what I would like to do (in single-user mode):
1. Mount an external USB drive (250 GB already formatted as Mac OS X Extended)
2. Copy various files and/or directories from my HD to the external USB drive (UNIX cp command)
I realize I could go spend $$ for the Disk Warrior or Data Rescue products (or something similar) that SHOULD help me recover my HD or files, but it seems silly to do this when I can see, touch and taste them from within single-user mode....
Comments? Suggestions?
TIA --
Trent
P.S. Once I've recovered my files, I'll try to reformat the HD and then reinstall the OS. And THEN go have Apple look at my machine (thank goodness for AppleCare coverage)!

Resolution:
1) Boot system in single-user mode (SUM) with external HD attached.
2) Execute the following UNIX CLI commands once SUM boot process is completed:
# fsck -fy
# mount -uw /
# mkdir /Volumes/target_directory
# mount -t hfs -w /dev/diskXXX /Volumes/target_directory
# cp -RXv /source_directory /Volumes/target_directory
Where XXX is the device-level name for your external HD's data partition. In my case this was /dev/disk1s2. It may take some experimentation to identify this device name if your system has multiple HD's.
3) Verify contents were successfully copied onto the /Volumes/target_directory.
Comments and observations:
- Do NOT use "/" as your source directory - cp will make a second (redundant) copy of /volumes/target_directory
- I was able to successfully copy ALL files off my HD despite the fsck command's "invalid node structure" error message with this simple procedure. YMMV, depending on the state of your HD.
- The repeated disk0s2: I/O error warnings displayed during the SUM boot process did not seem to have a negative effect on this procedure. I also received this same error warning intermittently as I navigated the mounted filesystem did not seem to be a problem, either. Again, YMMV.
Commercial software:
I downloaded ProSoft Engineering's Data Rescue 3 product (trial version) before spending $99 to attempt to recover my "bad" HD's data via mounting to a good system with FW target mode. It could not successfully complete its "QuickScan" process and immediately hung on block 0 of 390M during its "Deep Scan" process. The product did seem to function properly on an operational system. ProSoft's technical support was responsive and helpful but had no answer for my "Deep Scan" error.
I did not attempt to use Alsoft's Disk Warrior 4 product. I could not find any trial software available and was reluctant to spend $100 based upon the mixed reviews and comments on this discussion forum as well as other reviews. Alsoft does claim to address the "invalid node structure" error in their marketing materials. Hindsight being 20/20 - I saved $100 by using this simple procedure.
Final note:
Neither Leopard nor Snow Leopard's installation DVD could recognize the bad internal HD when trying to do a reinstall. While DiskUtil was able to "see" the bad internal drive it immediately failed when I tried to do an "erase and format". Took the system to my local Apple store and the Genius ran a tool called "SMART Utility" from Volitans Software (www.volitans-software.com). SMART utility confirmed that my HD was bad so it was replaced. AppleCare pays for itself (once again!).

Single user mode . using tail -f (command not found)

Have an empty computer with no systems disk as the installation CD start up will not go past the grey screen with the rotating logo before the panic crash page comes up and tells me to restart the computer.
Trying to boot into single user mode and then use the command tail -f to see contents of some of the logs... BUT I get the reply tail command not found ????

If the hard drive is empty, then you can only boot from the CD. Regardless of whether or not it has "tail," it won't do you any good. There are no logs.

Single user mode doesn't accept commands

Due to some kernel panics with an old G5 iMac, I wanted to run the memtest utility. After an initial test in a Terminal, I wanted to try again in single user mode, just to be sure.
Had no problem at all starting up (Cmd+S), didn't get any error messages in the boot messages. The ":/ root" prompt appears and I can enter commands. Yet no matter what I enter, I immediately get returned to the shell prompt. Command line editing works (emacs commands, clear screen etc.). Due to the lack of delay (even when e.g. entering "sleep 10"), I don't suspect it's just the output of the shell command that gets lost, it's not accepting anything at all, prompt doesn't reflect "cd" changes, nothing…
New install of Leopard, all updates applied, permissions repaired.

I can't picture what is doing this other than something missing or muxed, but perhaps it's time for a relatively painless Archive & Install, which gives you a new/old OS, but can preserve all your files, pics, music, settings, etc., as long as you have plenty of free disk space and no Disk corruption, and is relatively quick & painless...
http://docs.info.apple.com/article.html?artnum=107120
Just be sure to select Preserve Users & Settings.

Powerbook won't start, got message i don't understand in single-user mode

PowerBook G4 Mac OS X (10.3.9)
About a week ago my powerbook (purchased in Dec '03, running 10.3.9) froze while I was using it. I had to manually shut it off, and then it would not restart (got stuck on grey screen with gear). I was able to start it up again once in Safe Mode, at which point I downloaded and ran Macaroni. Upon reboot, it wouldn't start up at all, staying on the grey screen for 15-20 minutes before I gave up. Now, I've tried starting it in Single-user mode. At the command I typed "fsck -fy" and the following message was returned:
"Singleuser boot -- fsck not done
Root device is mounted read-only
If you want to make modifications to files,
run ' /sbin/fsck -y' first and then '/sbin/mount -uw /'
localhost:/ root# "
Does anyone have any idea what this means?
I am expecting the worse, I made a bootable back up in august, but was hoping to get it to start at least once more so i could update that back up or email myself some files. The only other possibly relevant info is that when it froze last week it started making really really loud repetitive noises (as if the hard drive was stuck?). For a while there I was also hearing an odd humming noise whenever i plugged in the AC adapter.
Well, any help would be truly appreciated.
thanks in advance..
PowerBook G4 Mac OS X (10.3.9)

The two observations may be related. It is possible that the power adapter has developed a fray or short, and is giving insufficient power for the hard drive to operate properly. Do you have another Mac you can connect the machine to via Target Disk Mode after getting a replacement power adapter?
I would also get a copy of Prosoft Data Rescue and an external hard drive that is Firewire at least as big as the internal hard drive. That will give you a chance to recover information if it is at all reachable.
If the directory is damaged Alsoft Disk Warrior may be able to repair it, but I'd only run that after determining Prosoft Data Rescue is unable to rescue any usable data.
I would not attempt to run any norton utilities on it, and if you have in the past don't do it again, as Disk Doctor and Speed Disk have been known to damage Mac OS X more than fix it.

Why can't I enter single user mode on my Mac Mini for an admin password reset?

Hi,
I recently created a new user account for my mac and deleted the old one, not realising that this was the only account with admin priveleges. As such, I no longer have access to administrator priveleges, and cannot grant them to my new user account.
I have tried to boot in single user mode and recovery mode but neither command results in any reaction on the part of my computer.
This thread follows on from a previous, unrelated disscussion:
BDAqua: If you hold alt key at bootup do you see a lock in the middle?
Yenots: No...what does this mean?
BDAqua: If it did, it would mean Firmware Password Protection was enabled, which prevents booting in other modes, so that's not the problem, are you using a wired Mac KB, or Windows KB?
Yenots: I'm using an 'Apple Keyboard with Numeric Keypad' [ http://store.apple.com/uk/product/MB110B/B/apple-keyboard-with-numeric-keypad-br itish ]
If you find me here BDAqua, hit me with your knowledge!
Any other contributions are welcome and, now we're under the right heading, will hopefully help other users who have encountered this problem.
Thanks, Cristo

Hi,
Thanks for the link to MacPilot, and the sexy screenshot. I found an archived version for 10.4 on the koingosw website. That solves getting into single user/safe mode. Though I'd be interested to see whether sudo nvram boot-args="-s" will result in single user boot.
As for creating administrator priveleges for my new user account, I've found a method which looks good:
     \single user mode\
     cmd-s
     \mount drive\
     mount -uw
     \open 'directory access'\
     lauchctl load /System/Library/LaunchDaemons/com.apple.opendirectory.plist
     \list users\
     ls /Users
     \change password\
     dscl . passwd /Users/<username> <password>
I think that this method intends that if I change the root users password I'll be changing the administrator password (as root is the only user with administrator priveleges), and subsequently be able to change my new user accounts priveleges using 'netinfomanager'. But I'm not 100%. Could you give me your opinion on this?
Furthermore, three keys 'L' 'O' and '(' aren't working on my keyboard, which means I can't try this until I find an intact keyboard to borrow. I was thinking maybe a mod version of the above instructions would work in terminal using sudo, so I could use the keyboard viewer to type the missing characters. If you have any ideas on constructing such a mod I would be interested to hear them.
Otherwise, Thank You for your help BDAqua! And enjoy your summer wherever you are.

Data back up from Single User Mode

Hello,
I have a problem with my 700 MHz iBook, dual USB, with OS X 10.3.9.
Unfortunately the OS doesn't start up because of "overlapped extent allocation" problem...
I would like to re-install the complete OS but before doing it, I would like to back up some directories.
Is it possible to save some data, by connecting an Ipod or some sort of external peripheral, from the Single User mode?
If yes, how can I do it?
Thank you in advance from your kind support.

Before giving up the ghost check out these:
http://docs.info.apple.com/article.html?artnum=25770.
Manually fix Overlapped Extent Allocation Errors without Disk Warrior
Overlapped overlapped extent allocation errors can be the bane of any Mac user's existence. Often, these errors go unnoticed until the problem becomes visible: your Mac might refuse to boot, crash unexpected, or worse, critical data might disappear from the Finder. Disk Utility can detect, but not fix overlapped extent allocation errors, and certain third-party utilities, such as Alsoft Diskwarrior, can fix them, but generally without reporting the consequences.
Overlapped extent allocation error occur when the file system thinks that two files are occupying the same area on the hard disk, hence overlapping on the same "inode," which is the structure which holds the location of the data blocks the file occupies, and also file permissions and flags.
Clearing the "overlapped" or "overallocated" extent allocation essentially means that you'll have to lose some data, because the only way to remove the overlap is to delete the file that's occupying the inode. So, if you suspect, or find out, that the guilty file is a critical system file that resides in one of the hidden system directories such as /etc /var /usr/ or visible system directories such as /System or /Library, and you don't want to reinstall the whole OS (which might not fix the overlapped extent allocation anyway), it's good to have another disk available to copy the files back to your original disk if necessary: a second bootable hard drive or a firewire drive connected to your Mac when you remove the misbehaving file. Just make sure that when you copy the file back to your boot disk that the permissions are correct, so it's best to use the "ditto" command, so that all sticky bits, flags, and permissions are preserved.
In case you didn't know, you don't have to boot from an install CD in order to check for overlapped extent allocations. All you need to do is restart your Mac, while holding down command + S to boot in "single-user mode."
At the command prompt that appears, type:
$ fsck -fy
If you have an overlapped extent allocation, you'll see:
"Overlapped Extent Allocation" (File 123456d)
No matter how many times you run fsck -fy, you'll never be rid of the error.
So, simply issue the following command:
find / -inum 123456 -print
Note the "d" was dropped, or any extra letter that appears after the inode number.
The find will return a file name that matches with the inode number, and the path to that file. If you remove the file then the fsck will not return this error next time you run it.
However, before you can delete the file(s) in single-user mode, you'll need to mount the file system. Type:
$ mount -uw /
When done, issue the "sync" command, and that will flush the write cache so that all pending writes are written from memory to the disk. Also, since most OS X 10.3 Macs use the HFS+ Journaled file system, it might be a good idea to disable the journal before booting into single-user mode by typing:
$ sudo diskutil disableJournal /
then re-enable it when done fixing the overlapped extents and rebooting normally:
$ sudo diskutil enableJournal /
Chris Anderson is a long-time Linux propellerhead who just got his first Mac, an ibook G4, and can't keep his hands off of it. He currently works as a "The Architect" and general visionary for a maker of world-class collectibles.
If you own Disk Warrior then it should be able to repair a drive with overlapped extents.
There are two backup utilities included in Unix - psync and rsync. You will find them in the /usr/bin/ directory. For documentation simply enter: man psync or man rsync. In order to write data while in single-user mode you need to issue the command: /sbin/mount/ -uw / (Note: there is a "space" between the "uw" and the "/".) To mount an external drive you will need to provide the mountpoint for it in place of the "/", e.g., "/Volumes/volname") without the quotes.

Single User Mode : Read Only Filesystem

I can't edit files in single user mode as Root. When I try to edit them I get a msg saying "Read Only Filesystem".
I have tried chmod with no evial. I want to change my .profile as root so cls='clear'.
Any ideas?
Also when I try to login to my account in single user mode it says that account does not exist. However I'm in that accunt right now!
Thank You.

When you boot up into single user mode, there is a single recognized user -- root. That's why they call it single-user mode and not multi-user mode.
When you boot up into single user mode, the disk mounts as read-only. You have to make it writeable in order to do anything to it. I forget the actual command but it displays on the monitor nearby where it gives the "fsck" command syntax when you first boot into it. It's something like "mount -uw /" or something to that effect. It is saying to mount the root drive ("/") with user write privileges.
Then just "pico /Users/Mephux/.profile" (although I profess that I don't understand why you have to edit this file as root).
(if you find that this solves your problem, or is actually helpful towards arriving at a solution to your problem, please consider clicking on either the "helpful" or "solved" buttons above)

Failure to boot in single user mode

Hi,
I have an iBook G3 900MHz G3 running 10.4.6. 384MB RAM, ~25GB free disk space.
it's running slow so I want to boot in single user mode and run applejack.
the trouble is, it won't boot in single user mode. when I hold command-s or command-v it just boots right to the GUI.
i've tried both command keys thinking that one might be broken.. no luck. I also have no trouble getting to single user mode on my G4 laptop.
I have not taken steps to disable single user mode.
any ideas?
thanks a lot

I think it would be worth a try to repair permissions and then boot from the Install disk to run Repair Disk in Disk Utilities. If you still cannot boot into single user mode after that, perhaps obtaining and running Disk Warrior can resolve the problem.
Bob N.
Mac Mini 1.5 GHz; iBook 900 mHz; iPod 20 GB Mac OS X (10.4.6)

Cannot edit sudoers file in single user mode.

I did not back up my sudoers file on my pro.
I made a change to it, adding my "test" user to be able to use sudo, but upon restarting, it didn't work, and I cannot edit the file via cd in single user mode.
I mounted the drive, changed permissions, but it seems that I don't have the option to use vi, visudo, vim.
Thanks for the help.

I mounted the hdd using the command below.
I then made sure I could get to the file by cd to it.
Then once I was there, i would attempt to type vis <tab> to complete, and visudo does not show up. Typed in visudo, nothing. This was on a brand new mb pro. I can wipe it out, but I would rather figure out why its not working.
The reason for all this is I have to give it to a user at my job. We don't want them to have admin rights to install anything they want, but they need to use sudo in X11 for compiling and such. I read online that I can edit/add their username to the sudoers file, and allow them the right to sudo for compiling, starting apache on their laptops, etc.
Thanks.

How to mount USB & CDROM drives from single user mode - Solaris boot disk?

Hi All,
I need to carry out ufsrestore on a single newly replaced system disk (no redundancy / mirroring) from either USB or CDROM drives from the following steps:
( i ) GRUB => e, e, cdrom –s, Enter, b (boot from Solaris 10 x86 media).
( ii ) Choose menu 1 for Install Solaris Interactive Mode to reach single user mode.Below are the commands that I have tried in single user mode without success:
mount –r –F pcfs /dev/dsk/c1t0d0p0 /cdrom (after unmount Solaris CD)
mount: /dev/dsk/c1t0d0p0 is not a DOS filesystem.
svcadm –v enable smserver
svcadm: Pattern ‘smserver’ doesn’t match any instances
svcadm enable autofs
svcadm: Pattern ‘autofs’ doesn’t match any instances
devfsadm
devfsadm: mkdir failed for /dev 0s1ed: Read-only file system
mkdir /mnt
mkdir: Failed to make directory “/mnt”; Read-only file systemPart of the problem is due to the current READ ONLY filesystems which does not allow the creation of mount point such as /mnt.
I have been able to create both / root (/dev/dsk/c1t0d0s0) and /export/home (/dev/dsk/c1t0d0s0) filesystems with newfs that are awaiting for restore using ufsrestore.
The only option I am left with is to attach a secondary disk to install Solaris 10 on either of them before bring the system to multi-user mode so that service such as volmgt, autofs, volfs are available to access USB & CDROM drives.
Any suggestion on how to resolve this issue?
Many thanks,
Jack

Hi JKGN,
Is the directory a located under the root filesystem. ie /a? Are there any other mount point for say USB drive as well? I am not in a position to try it out right now but will get back
to you soon on whether /a exist or not.
Btw, the last thing I managed to do on this system at the time was added a secondary 1TB internal disk with the intention to restore both / and /export/home data onto this disk while
making use of all the disk device management services such as the following services only available in a fully installed Solaris system (both single & multi-user modes) installed on the
primary disk:
# svcs smserver
STATE          STIME    FMRI
online         Jun_08   svc:/network/rpc/smserver:default
# svcs autofs
STATE          STIME    FMRI
online         Jun_08   svc:/system/filesystem/autofs:default
# devfsadm
# iostat -En
c1t0d0           Soft Errors: 0 Hard Errors: 0 Transport Errors: 0
Vendor: ATA      Product: SAMSUNG HD321KJ Revision: 0-11 Serial No:
Size: 320.07GB <320072932864 bytes>
Media Error: 0 Device Not Ready: 0 No Device: 0 Recoverable: 0
Illegal Request: 41 Predictive Failure Analysis: 0
c0t0d0           Soft Errors: 0 Hard Errors: 5 Transport Errors: 0
Vendor: PHILIPS Product: DVD+-RW DVD8801 Revision: AD21 Serial
Size: 17.54GB <17538875392 bytes>
Media Error: 0 Device Not Ready: 5 No Device: 0 Recoverable: 0
Illegal Request: 10 Predictive Failure Analysis: 0
c2t0d0           Soft Errors: 0 Hard Errors: 0 Transport Errors: 0
Vendor: JetFlash Product: Transcend 16GB   Revision: 1100 Serial No:
Size: 0.00GB <0 bytes>
Media Error: 0 Device Not Ready: 0 No Device: 0 Recoverable: 0
Illegal Request: 7 Predictive Failure Analysis: 0
# rmformat
Looking for devices...
     1. Volmgt Node: /vol/dev/aliases/cdrom0
        Logical Node: /dev/rdsk/c0t0d0s2
        Physical Node: /pci@0,0/pci-ide@1f,1/ide@0/sd@0,0
        Connected Device: PHILIPS DVD+-RW DVD8801 AD21
        Device Type: DVD Reader/WriterHowever, I was disappointed that "iostat -En" has not found the secondary disk (1 TB) even though it was available earlier, for Solaris installation as the only disk on the same system.
As a result, I am left with no option but the need to rebuild this system with only a single primary disk while in single user mode. However, the single user mode that I am in is the
one from Solaris installation disk with restrictive (_cannot create folder for mount point or running disk management utilities_) capability such as those services just covered, compared to one from a completed Solaris installation system with full access to all filesystems and utilities / commands in general.
I would very much value your assistance on how to mount both CD & USB in this restrictive limited Read Only OS (assume that it is running from memory) in order to get complete access to
the blank primary disk so that full restore with ufsrestore could take place.
Thanks in advance,
Jack
Edited by: 797805 on 9/06/2012 04:15

Stuck while booting in single user mode. How to go back?

Guys. I'd appreciate your advice very much - this concerns my main system.
MacBook 3,1 with OSX 10.5.? (latest)
Did: activate single user boot in Onyx; reboot
Problem: stuck at boot (apple logo & spinning wheel on gray background for 2hours+). Persistent across reboots.
No different results for this key combinations: cmd-opt-p-r, power button for 5 sec whilst without battery/cable, cmd-s, C (possibly not recognized due to firmware password) Power button held down from switch-on moment makes the light flash a few times, produces a beep but no improvement.
Interestingly pressing alt lets me choose the os (HD or Leopard install disc) but gets stuck the same way regardless. It boots into Ubuntu tho.
I have a TIme Machine disk that I can restore from, and can read from the internal Leopard HD while in Ubuntu.
So, please: how do I get it to boot? I'd set the nvram bootargs="" but from where...

Sorry, don't know how you'd recover from the apparent limbo you're in, but this would agree with the explanation you already hit upon.
http://support.apple.com/kb/HT1352
Features of Open Firmware Password Protection
Intel-based Mac computers Power PC Intel
Blocks the ability to use the "C" key to start up from an optical disc.
Blocks the ability to use the "D" key to start up from the Diagnostic volume of the Install DVD.
Blocks the ability to use the "N" key to start up from a NetBoot server.
Blocks the ability to use the "T" key to start up in Target Disk Mode (on computers that offer this feature).
Blocks the ability to start up in Verbose mode by pressing the Command-V key combination during startup.
Block the ability to start up a system in Single-user mode by pressing the Command-S key combination during startup.
Blocks a reset of Parameter RAM (PRAM) by pressing the Command-Option-P-R key combination during startup.
Requires the password to enter commands after starting up in Open Firmware, which is done by pressing the Command-Option-O-F key combination during startup.
Blocks the ability to start up in Safe Boot mode by pressing the Shift key during startup.
Requires the password to use the Startup Manager, accessed by pressing the Option key during startup (see below).

Mounting a dmg in single user mode

When ever I try to mount a .dmg in single user mode using "hdiutil mount /path/to/dmg" I get no errors but I can't actually access the mounted dmg, it never appears in /Volumes
My question is how do you access a mounted dmg is single user mode

I've run into similar difficulties. I don't know about 10.6, but in 10.5.8 the HDI driver appears to load fine. (You can check that with the kextstat utility.)
In fact, my 10.5 Install CD uses hdik to create RAM disks early in startup. However, the same calls to hdik fail when I try them in single-user mode.

IMac G5 won't boot in normal and safe mode, but will from single-user mode

Hello everyone,
I'm quite new here, so I try to do my best if you have a question.
Yesterday, someone nearby me had a iMac G5 (Powermac8,1), and he sayd, that the computer sometimes will boot, sometimes not.
I did test it, I thought it was running fine, but when I played some music in iTunes, it was stuck on 9 seconds, and crashed (with a kernel panic). The guy also sayd, that there was nothing important on the computer, so a clean install was fine.
Now, the problem is, that it will not boot in normal mode (without anything pressed on boot), also it won't in safe mode (shift-boot), but it will, when I enter single-user mode, mount the hard drive and exit from single-user mode so it will go futher on booting. Sometimes it will not, and immediately gives you a kernel panic in single-user mode, but it will 90 percent of the time.
Then you've got another problem: when it's running in the normal desktop from single-user mode, it'll be stuck after some time again. If I look into the Kernel Panic file created, most times it's because of Spotlight indexing, so I disabled that.
He also gave me the disks (Apple Hardware Test and Extra Applications, and iMac G5 Mac OS X Install Disks 1-3) that came with the Mac. He sayd that I could use them, but I think he didn't test out the SuperDrive, because when I insert a disk, it will try to read, but it will make 2 same sounds, and quits after 10 tries, when it will spit the cd out. Also normal (audio) disks.
Also, I must hurry with the commands for mounting and exiting in single-user mode, or it will just not boot.
In all cases, after 30-45 seconds from pressing the power button, the fan will start blowing at full speed, and it will stop after the exit command in Single-user mode. That's weird.
I can't do anything with the SuperDrive, I can't normally boot in Mac OS X except for Single-user mode (but I don't think he would like to do that every time the computer boots up), and I have very limited time when Mac OS X arrived on the desktop.
When booting in Verbose mode, it will be stuck on this:
AppleSMU::PMU vers = 0x000d004c, SPU vers = 0x15, SDB vers = 0x01,
(and sometimes ends with a kernel crash by fsck_hfs)
Things I've tried (without any success):
- /sbin/fsck -fy (in single-user mode)
- Disabling Spotlight and mds
If you want some more information, feel free to ask!
Greetings
-MrYoranimo
PS: My main language is Dutch, so my English can be bad at some points.

Thank you for your support! This reply is a little bit late, because I was to the camping this weekend.
The only thing I sure do know, is that the iMac has a bad SuperDrive. That's one problem, but I don't really wanna use it, and you fix everything by Single-user mode and when I get to the desktop to test things and change stuff in the Preference Panes.
What also came to my mind was that there also is a problem with the videocard (driver), because sometimes when I boot into Single-user mode, I can see some white pixels which aren't supposed to be there. And when booting from SUM you can see that some of the colors are different and there are weird patterns on the screen.
I also tried to setup a NetBoot server on this computer (MacBook Mid 2010) with just Lion 10.7.4 on it, but I'm not that expert and I didn't really find the good posts on the Internet, although I tried it with the Server applications and both Server applications and DeployStudio. But I didn't succeed.
I don't really like buying a new FireWire hard disk or external FireWire dvd reader/writer, except if it has USB support, because my MacBook doesn't support FireWire, and I really wanna make use of it then.
If I know more or have fixed it, I will surely post again here with what I did to fix it (if no one else has posted here already ).

Won't boot normally or in recovery and single user mode, safe mode hangs up halfway

iMac locked up with visual glitches while playing the Mac beta client of League of Legends. Had to force a shutdown by holding the power button. Now it won't boot; after the Apple logo and spinning wheel I just get a white screen. I tried launching in recovery mode, that didn't work. Then I tried safe mode; the bar filled a little over half and then nothing but white screen. I was able to boot single user mode once; ran fsck -fy and rebooted, still white screen. Now I can't get back to single user mode. I booted with command option P R to reset the NVRAM and got the second chime, but still nothing.
Luckily all my important files are in the cloud, but I'm really hoping my computer isn't completely dead. I haven't had any issues in the past. I've even been playing LoL for over a month with no issues, until now when I tried to play the newer game types, Dominion and ARAM; both caused visual glitches forcing shutdowns. I was able to restart my computer with no problem after the first two visual glitches, but after the last one I am stuck at the white screen as I described above.
Thanks in advance for your help!

I'd bet the drive is damaged. You could try reformatting if possible. Again, you are booting from the Recovery-10.8.2 disk if you can. If you can't, then you will need to use the installer disc that came with the computer.
Install or Reinstall Lion/Mountain Lion from Scratch
Be sure you backup your files to an external drive or second internal drive because the following procedure will remove everything from the hard drive.
Boot to the Recovery HD:
Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.
Erase the hard drive:
1. Select Disk Utility from the main menu and click on the Continue button.
2. After DU loads select your startup volume (usually Macintosh HD) from the
      left side list. Click on the Erase tab in the DU main window.
3. Set the format type to Mac OS Extended (Journaled.) Optionally, click on
        the Security button and set the Zero Data option to one-pass. Click on
      the Erase button and wait until the process has completed.
4. Quit DU and return to the main menu.
Reinstall Lion/Mountain Lion: Select Reinstall Lion/Mountain Lion and click on the Install button.
Note: You will need an active Internet connection. I suggest using Ethernet if possible
            because it is three times faster than wireless.

Why won't single user mode recognize /sbin/mount command?

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