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.

Similar Messages

  • 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.

  • 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. 

  • 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.

  • 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

  • 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.

  • 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).

  • 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)  

  • I changed my wheel group properties to no access at top disk level.  I messed up, how can I change back in single user mode "command s" as I am now in Thailand and not able to access startup disks?

    I messed up, I changed my "Wheel group" properties to No Access ( or something other than the default) at the top level of my startup disk "Macintosh HD".   Now my computer won't start up, I just get the spinning wheel of death.    I also am in Thailand right now, so I cannot go to a Genius at an apple store, nor do I have startup disks available.
    So I was hoping there was a way to change back the properties of my disk (Volume) in single user mode (via Command +s) during startup, i.e. can I do a chmod command on the Macintosh HD listing under the Volume Directory.    Or where do i fix this?   Is it fixable without startup disks, etc...
    THANKS FOR ANY HELP!!!!
    If you could also please let me know you have an answer, I WOULD REALLY APPRECIATE IT!!! 
    thanks so much
    mark
    <Edited by Host>

    Thomas,
    Thanks for the info on command-R, didn't know about that!!!
    Yes I changed the sharing "Wheel Group" permissions on my hard drive via Get Info.    But that's all I did.    And then most of the apps wouldn't respond with anything.    So not knowing I did something stupid, I decided to re-boot, and then nothing but the Wheel of Death at startup.
    I was trying to limit access to my computer on this network, changed my public folder settings, and then I thought why not the whole hard drive, but at that time I had no idea what the "Wheel Group" was... so I shouldn't have touched it, BUT IT DID ...... argggggg....
    I managed to go to an internet cafe & research the problem yesterday.    I used the command +s single mode to get in, and then did the necessary steps to mount the drive so I could make changes.   I basically did this:
    Boot into single-user mode (boot while holding down CMD-S)
    Follow the on-screen instructions to mount the file system as read-write (a fsck command followed by a mount command)
    Type the following: "chmod o+r /" followed by "chmod o+x /"
    Type "exit" to leave single user mode and complete the boot sequence.
    I found it at this link http://forums.macrumors.com/showthread.php?t=416180
    It worked... thank God!!!   Well so far so good.   
    I was going to try my own fix by chmod on the Hard drive listed under Volumes directory, but that doesn't seem to match the info under Get Info Window.    So I just used the fix above.    I probably should now go and do "Disk Utility - repair permissions", however I am a little gun shy right now, so I will probably wait until I am back in the States so I can go to an Apple store if it messes up.   Right now I'm following the "if it ain't broke, don't fix it" MOTTO...
    So Thomas I just wanted to say THANKS for replying so quickly, and I really appreciate your help!!!
    (yes I know I shouldn't have used my email addresses, but I WAS DESPERATE, but that's still no excuse)
    Hopefully maybe this thread will help someone else out in the future....
    Okay, thanks again!
    Mark

  • Keyboard doesn't respond at login window... works in Single User mode

    I have a G4 xServe (server 10.3) that won't accept keyboard input at login window, but the same keyboard, usb port, works fine when I'm booted into Single User Mode.
    Booting into Single User mode, something interesting gets posted during boot:
    "AppleCPUThermo got unsupported command"
    Any thoughts?

    Did you find a resolution to this issue? After I installed the latest security update to OSX Server 10.4.8 I am now experiencing the same problem. Any insight would be greatly appreciated.

  • Command Line Expert Needed: Deleted hostconfig (+ others) - boots to single user mode only !

    Mac OS X Tiger 10.4.11
    Deleted folders/files when logged in as root user. (don't ask!)
    On restart , wont boot up , get grey screen with white apple logo the black screen with command line: localhost:/ root#
    Started up from install cd - repaired permissions (ran twice) &amp; verified hard drive . All okay.
    Restarted but still goes back into command line with same localhost:/ root prompt
    Tried a bunch of different things as per advice on these boards - discovered that there is no hostconfig file.
    Restarted into verbose mode.
    Here are the lines that i think may reveal exactly what I messed up - and hopefully someone out there has an idea how I can try to fix without having to do an archive/install.
    BSM auditing present
    disabled
    rooting via boot-uuid from /chosen: (here a very long string of numbers and letters looks like a password)
    Then a long line about
    "got boot device = IOService:/MacRISC2PE ........."
    Then, the following
    "BSD root: disk0s3, major 14, minor 2"
    "CSRHIDTransitionDriver::stop"
    "IOBluetoothHCIController::start Idle Time Stopped"
    (AND HERE'S THE BIGGIE:)
    /etc/rc: line 93: /etc/hostconfig: No such file or directory
    Apr  1. 06:01:44 launched: /bin/sh on /etc/rc terminated abnormally, going into single user mode
    localhost:/ root#
    I'm pretty sure I messed thing up pretty well - was mainly network/server folders and files - definitely samba, which I think I deleted, and under "network" in the finder, I also might have deleted my computer from the server list
    As an aside in case this provides any insight, when I go to the terminal app when starting up from install cd, the prompt reads :
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    I'm also able to see the contents of my hard drive when using disk utility from install cd and and trying to "mount image" ---
    Everything looks intact in terms of folders/files in my user account, but in the /root folder, there's only /library - which is empty.
    Any help, insight, troubleshooting and even scolding - will be welcome! I need this thing booted
    Cheers

    I do not have a backup. Should I back up before I try doing a reinstall of the os x?
    That's also known as shutting the barn door after the horse has bolted.
    It can't hurt, but it's not going to help much.
    Camelot: when you say "apps and user content should stay intact" - doesn't sound very definitive. Are there any variables that come into play?
    No.. generally it's pretty reliable, but yours is an odd situation. I wouldn't expect to lose any user data, just CYA
    I do have a start up disk along with some apps that I created in retrospect many years ago ....(I think it's os x 10.2.8) Can I use this to boot up and then just navigate to my user files so I can get some things done that I need to?
    Unlikely. For one have you even tried restoring from your Retrospect backup? (it's not the most reliable system).
    Secondly, you can't boot from your Retrospect backup, so you'll need to restore that system to boot from it. Have you got a second disk to restore to (you do NOT want to restore 10.2.x over your 10.4.x system).
    in terms of "random deleted files" : not entirely random
    Ok, maybe not entire random, but it's also somewhat unknown. You need to have some idea of what files you're trying to restore, but if you haven't got them in a backup where are you going to get them from?
    You cannot just take old copies from your 10.2.x system and hope they'll work (in case that's what you're thinking).
    The BEST solution is to boot from the 10.4.x installer disk and let it do its thing.
    And for what its worth, Unauthorized access attempts, in and of themselves, are not a cause for concern since they were clearly caught by the OS. It's the access attempts that succeed (and are not logged) which are more of an issue.

  • Transfer file in Single User Mode (Command S)

    Can I mount my iPod as external drive and transfer my documents in Single User Mode? or any other mode? I just cannot login as normal. I want to backup my docs before refresing the OS.

    You say 'Documents' not 'Music' so I hope you mean files stored on there using it in Disc Mode not iTunes files?
    Boot in Single User Mode
    at the root# prompt enter
    CD /Volumes
    ls
    And see if a) the iPod shows and b) your backup drive shows
    If so, the basic command is cp source destination but you must give the complete and correct paths here so post the drive names if you need clarification.

  • Start SQL Server in single user mode with parameter -m doesn't work well

    C:\Windows\system32>net start mssqlserver /m "Microsoft SQL Server Management St
    udio - Query"
    The SQL Server (MSSQLSERVER) service is starting.
    The SQL Server (MSSQLSERVER) service was started successfully.
    C:\Windows\system32>sqlcmd -S . -e
    1> go
    1> select @@servername;
    2> go
    select @@servername;
    myserver
    (1 rows affected)
    1>
    As you can see, I'm still able to connect with sqlcmd prompt to SQL Server. According production doc of SQL Server 2014, it should not be conncting by sqlcmd. it shall only be connected by SSMS.
    below the original doc on msdn:
    Start SQL Server in Single-User Mode
    Provide Feedback
    Under certain circumstances, you may have to start an instance of SQL Server
    in single-user mode by using the startup option -m. For
    example, you may want to change server configuration options or recover a
    damaged master database or other system database. Both actions require starting
    an instance of SQL Server in single-user mode.
    Starting SQL Server in single-user mode enables any member of the computer's
    local Administrators group to connect to the instance of SQL Server as a member
    of the sysadmin fixed server role. For more information, see Connect to
    SQL Server When System Administrators Are Locked
    Out.
    When you start an instance of SQL Server in single-user mode, note the
    following:
    Only one user can connect to the server.
    The CHECKPOINT process is not executed. By default, it is executed
    automatically at startup.
    Note
    Stop the SQL Server Agent service before connecting to an instance of SQL
    Server in single-user mode; otherwise, the SQL Server Agent service uses the
    connection, thereby blocking it.
    When you start an instance of SQL Server in single-user mode, SQL Server
    Management Studio can connect to SQL Server. Object Explorer in Management
    Studio might fail because it requires more than one connection for some
    operations. To manage SQL Server in single-user mode, execute Transact-SQL
    statements by connecting only through the Query Editor in Management Studio, or
    use the
    sqlcmd utility.
    When you use the -m option with sqlcmd or
    Management Studio, you can limit the connections to a specified client
    application. For example, -m"sqlcmd" limits connections to a
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    sqlcmd client program. Use this option when you are starting
    SQL Server in single-user mode and an unknown client application is taking the
    only available connection. To connect through the Query Editor in Management
    Studio, use -m"Microsoft SQL Server Management Studio - Query".
    Shawn

    Hi Shawn Xiao,
    For starting SQL Server instance in single user mode, we can add –m; parameter in SQL Server Configuration Manager, also we can run CMD with ‘Run as administrator’ and input the following statement.
    NET START MSSQLSERVER /m
    I do a test in SQL Server 2014 Express version, after starting SQL with Single User Mode, SQL Server will only accept one connection. If you connect to SQL Server with a user account, the following error will occur.
    Login failed for user ‘domain\username’. Reason: Server is in single user mode. Only one administrator can connect at this time.
    However, in your situation, you can connect to SQL Server and run T-SQL statement successfully, it can be due to connection with the administrator account in your sqlcmd.
    For more information, you can review the following article.
    http://zarez.net/?p=117
    Regards,
    Sofiya Li
    Sofiya Li
    TechNet Community Support

  • Booting in single user mode to trouble shoot grey screen the boot stops at "CODE SIGNING .... clearing CS_VALID" will not command c past - stuck

    booting in single user mode to trouble shoot grey screen the boot stops at "CODE SIGNING .......... clearing CS_VALID" - cannot command C past - just stuck

    Hi opjml0,
    Welcome to the Apple Support Communities!
    If your Macbook is starting up to the gray screen, I suggest the steps in the following article.
    Mac OS X: Gray screen appears during startup
    http://support.apple.com/kb/ts2570
    I hope this helps,   
    -Joe

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