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  • Building the Bootsector of BIOSLOADER

    - by Kate Moss' Open Space
    Windows CE is a 32 bits OS since day one, so it makes sense tools shipped with PB, compiler, linker, assembler and etc, are for targeting to 32 bits system. But occasionally, if you are developing x86 based system and especially working on some boot code, such as boot sector of BIOSLOADER, that will be a problem. Normally, as PB provides the prebuilt boot sector image but if you ever need to rebuilt it, what should you do? You may say as it's an x86, perhaps you can use VS or Windows SDK to build it. But unfortunately, today's desktop Windows tool chains are also 32 or even 64 bits only, you need to find something older. VC++ 6.0, but how can you find one? This Website http://thestarman.pcministry.com/asm/masm.htm arranges some useful resources. Basically, you need 2 thing, the 16 bits MASM and 16 bits linker. Just make it even easier for you Download http://download.microsoft.com/download/vb60ent/Update/6/W9X2KXP/EN-US/vcpp5.exe for Assembler (MASM). Download http://download.microsoft.com/download/vc15/Update/1/WIN98/EN-US/Lnk563.exe for the Linker. And then just extract the archives and what you need is ml.exe, ml.err and link.exe

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  • How to backup boot information of a PC's Hard Disk?

    - by Bear Bear
    I just installed Windows 7 on a partition of my hard disk and I'm planning to install Vista and Windows 8 on other partitions on the same disk, and maybe a few Linux distributions too. Before I install other Operating Systems, I would like to backup the boot information, just to make sure I can get back to Windows 7 in case anything goes wrong with the booting data. I already made a backup of the MBR using MBRFix but I'm wondering if I should save some Boot Sector from the Windows 7 partition? I noticed that Windows Vista install DVD has a "bootrec.exe" utility in the recovery console (Shift+F10) and it has some options to rewrite the boot sector of the partitions. Therefore I wonder if there is any utility (preferably on Hiren's BootCD) to backup/write the boot sector I would also like to know how to backup the boot data of a Linux installation

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  • Restoring MBR, partition table, and boot sector of memory card without data loss ("USBC")

    - by Synetech
    Abstract I have a FAT32 memory card that when inserted into a computer causes Windows to prompt to format it. The card is definitely not supposed to be blank and has a bunch of files on it. Symptoms Using a hex-editor/disk-viewer, I examined the card and found that several sectors/clusters have been overwritten with something that has a signature of USBC at the start of the sector. Specifically, the master boot record (and partition table) is gone (hence Windows thinking the card is blank and needing to be formatted), as are the boot sectors (they have the USBC signature and a volume label of NO NAME and partition type of FAT32). Fortunately, it looks like both copies of the FAT are almost entirely intact (a few FAT entries at the start of a cluster here and there seem to be overwritten by USBC). The root directory is also nearly intact—I can see the volume label entry and subdirectory listings, but one sector is overwritten. (There are no more instances of USBC after the last one in the FAT2.) Hypothesis These observations seem to indicate some sort of virus that erases a few key filesystem structures, and then overwrites a few extra sectors here and there. Googling it seems to corroborate the idea of a virus, except that others report a file called USBC which does not apply here, and in fact, could not be possible since there is no filesystem to even see files. I cannot find any information about a virus with these symptoms, nor a removal tool. (I can't help but wonder if it is actually due to an autorun virus prevention tool.) Question I can likely fix the FAT corruption since they are mostly contiguous chains and maybe even the lost sector of the root directory, but does anyone know of a convenient way to restore or (re)create the MBR/partition table and boot sectors (without formatting or overwriting the data)?

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  • How to use C to write to flash drive bootsector despite error 'Failed to open file to write.:Permiss

    - by updateraj
    My goal is to manipulate the boot-sector in my flashdrive (volume E:) I am using XP. I am able to read the boot-sector FILE *fp_read = fopen("\\\\.\\E:", "rb"); /* Able to proceed to read boot sector */ however i am not able to open the file to write using fopen in 'wb' mode. FILE *fp_read = fopen("\\\\.\\E:", "wb"); /* Unable to proceed due to Failed to open file to write.:Permission Denied */ The flash-drive is not in use at the moment of execution. Hex-editors are able to manipulated boot sector etc, i believe it possible to do so in c. Any suggestion or insight to overcome the access problem so as to be able to write?

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  • writing boot sector code

    - by JGC
    hi I want to write a code which put something in bootsector but when I run the assembly 8086 code which does this purpose, nothing happens. does any one know what can I do or does any one has code (in any language) which answer my need?

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  • Need to get a file written to a floppy.

    - by dboarman-FissureStudios
    I asked this question over on SO. I have tried dd if=kernel.sys of=/dev/fd0 bs=512 seek=1 to get this file to write to the floppy. It is a kernel shell that must be written to the sector immediately following the bootsector of a disk to boot the PC. No matter what I've tried, for some reason, kernel.sys is not writing to the floppy. I know the bootstrap loader is being written and executed. However, it cannot find the kernel to load the shell. Any ideas on what I am doing wrong? I mean, really, how is it so difficult to get this file written to a floppy? OpenSUSE 11.2

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  • Converting a PV vm back into an HVM vm

    - by wim.coekaerts
    I have been doing some Oracle VM benchmark stuff in the last week or 2 in my off hours and yesterday I wanted to convert one of my VMs that was based on a paravirt kernel into a vm that just boots as a regular hardware virt VM with a standard x86-64 kernel. It took me a little while to figure out the fastest way so now that I have it pretty much down I wanted to share the steps. A PV kernel uses pygrub and a paravirt kernel image that lives on the vm image virtual disk. since this disk image does not have to be bootable it doesn't contain a boot sector and if you just restart the VM in hvm mode the virtual bios will just not do much as it can't start the boot process from disk The first thing I do is make a backup of my vm.cfg file :-) and then edit it as follows : the original file contains : bootloader = '/usr/bin/pygrub' I replace that with : acpi = 1 apic = 1 builder = 'hvm' device_model = '/usr/lib/xen/bin/qemu-dm' kernel = '/usr/lib/xen/boot/hvmloader' then changing the disk files. I change my xvd disks to hd disks and I copy over the iso image of my instal lDVD. In the case of my VM template it was based on OL5U4 So I downloaded Enterprise-R5-U4-Server-x86_64-dvd.iso and added it as a cd device. disk = ['file:/ovs/OVM_EL5U4_X86_64_11202RAC_PVM/System.img,xvda,w', 'file:/ovs/OVM_EL5U4_X86_64_11202RAC_PVM/Oracle11202RAC_x86_64-xvdb.img,xvdb,w', ] to disk = ['file:/ovs/OVM_EL5U4_X86_64_11202RAC_PVM/System.img,hda,w', 'file:/ovs/OVM_EL5U4_X86_64_11202RAC_PVM/Oracle11202RAC_x86_64-xvdb.img,hdb,w', 'file:/ovs/OVM_EL5U4_X86_64_11202RAC_PVM/Enterprise-R5-U4-Server-x86_64-dvd.iso, hdc:cdrom,r', ] boot='d' for the network devices (vifs) I change : vif = ['bridge=xenbr2,type=netfront'] to vif = ['bridge=xenbr2,type=ioemu'] That should do it. Next, inside the VM, I copy over the regular kernel rpm that I want to end up running in hvm mode. In this example case it was : kernel-2.6.18-164.0.0.0.1.el5.x8664.rpm. I will use that later on in the process. I put this kernel simply in /root At this point I just start the vm with xm create vm.cfg and start my vnc console to the vm console. Oracle Linux will boot from the iso image, I just go through the install steps and click on UPgrade existing (not re-install). Because the VM is the same as the ISO the install won't actually do anything and it will run through instantly. When the "Reboot" button pops up, don't reboot. Switch to the command prompt console. hi alt-f2 to go to the shell prompt. Now it's easy : umount /mnt/sysimage/boot cd /mnt/sysimage chroot . mount /dev/hda1 (if that was your /boot partition) export PATH=/sbin:$PATH (just to clean that up) edit /etc/modprobe.conf and comment out the xen modules (just put a # in front) Install grub. if your /boot is hda1 then that is (hd0,0) $ grub root (hd0,0) setup (hd0) exit grub now you have a good bootsector, grub installed and you have your grub.conf file Install the new kernel cd root (this is your old /root in your pv image) rpm -ivh remove (or comment out) boot='d' in your vm.cfg restart the VM and you should be good to go, regular grub should start and load your environment. Caveats : this assumes you used labels for your filesystems. if /etc/fstab were to have devices listed then you would have to rename these device before rebooting as well. If you had a /dev/xvda disk then this would be /dev/hda or /dev/sda. All in all it is a relatively short and simple process.

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  • Converting a PV vm back into an HVM vm

    - by wim.coekaerts
    I have been doing some Oracle VM benchmark stuff in the last week or 2 in my off hours and yesterday I wanted to convert one of my VMs that was based on a paravirt kernel into a vm that just boots as a regular hardware virt VM with a standard x86-64 kernel. It took me a little while to figure out the fastest way so now that I have it pretty much down I wanted to share the steps. A PV kernel uses pygrub and a paravirt kernel image that lives on the vm image virtual disk. since this disk image does not have to be bootable it doesn't contain a boot sector and if you just restart the VM in hvm mode the virtual bios will just not do much as it can't start the boot process from disk The first thing I do is make a backup of my vm.cfg file :-) and then edit it as follows : the original file contains : bootloader = '/usr/bin/pygrub' I replace that with : acpi = 1 apic = 1 builder = 'hvm' device_model = '/usr/lib/xen/bin/qemu-dm' kernel = '/usr/lib/xen/boot/hvmloader' then changing the disk files. I change my xvd disks to hd disks and I copy over the iso image of my instal lDVD. In the case of my VM template it was based on OL5U4 So I downloaded Enterprise-R5-U4-Server-x86_64-dvd.iso and added it as a cd device. disk = ['file:/ovs/OVM_EL5U4_X86_64_11202RAC_PVM/System.img,xvda,w', 'file:/ovs/OVM_EL5U4_X86_64_11202RAC_PVM/Oracle11202RAC_x86_64-xvdb.img,xvdb,w', ] to disk = ['file:/ovs/OVM_EL5U4_X86_64_11202RAC_PVM/System.img,hda,w', 'file:/ovs/OVM_EL5U4_X86_64_11202RAC_PVM/Oracle11202RAC_x86_64-xvdb.img,hdb,w', 'file:/ovs/OVM_EL5U4_X86_64_11202RAC_PVM/Enterprise-R5-U4-Server-x86_64-dvd.iso, hdc:cdrom,r', ] boot='d' for the network devices (vifs) I change : vif = ['bridge=xenbr2,type=netfront'] to vif = ['bridge=xenbr2,type=ioemu'] That should do it. Next, inside the VM, I copy over the regular kernel rpm that I want to end up running in hvm mode. In this example case it was : kernel-2.6.18-164.0.0.0.1.el5.x8664.rpm. I will use that later on in the process. I put this kernel simply in /root At this point I just start the vm with xm create vm.cfg and start my vnc console to the vm console. Oracle Linux will boot from the iso image, I just go through the install steps and click on UPgrade existing (not re-install). Because the VM is the same as the ISO the install won't actually do anything and it will run through instantly. When the "Reboot" button pops up, don't reboot. Switch to the command prompt console. hi alt-f2 to go to the shell prompt. Now it's easy : umount /mnt/sysimage/boot cd /mnt/sysimage chroot . mount /dev/hda1 (if that was your /boot partition) export PATH=/sbin:$PATH (just to clean that up) edit /etc/modprobe.conf and comment out the xen modules (just put a # in front) Install grub. if your /boot is hda1 then that is (hd0,0) $ grub root (hd0,0) setup (hd0) exit grub now you have a good bootsector, grub installed and you have your grub.conf file Install the new kernel cd root (this is your old /root in your pv image) rpm -ivh remove (or comment out) boot='d' in your vm.cfg restart the VM and you should be good to go, regular grub should start and load your environment. Caveats : this assumes you used labels for your filesystems. if /etc/fstab were to have devices listed then you would have to rename these device before rebooting as well. If you had a /dev/xvda disk then this would be /dev/hda or /dev/sda. All in all it is a relatively short and simple process.

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  • WIndows 7 cannot boot - bootrec reports FS not found or corrupt

    - by purecharger
    For 3 days now I've been unable to boot into my Windows 7 partition, and all my research has been to no avail. I'm hoping someone here has more ideas on how to fix this. When I boot up now, I get the black screen with BCD error that says theres no valid file system or it may be corrupt (pardon my lack of detail, no copy/paste is available then). When I boot with the Windows 7 disc and go into repair tools, no operating system is found, and attempting to automatically repair the problem fails with Unknown Operating System (Unknown Disk) or something similar. When I drop into the command prompt, I am able to see and navigate my C:\ drive without issue. I attempt to use bootrec: C:\> bootrec /ScanOS Finds C:\Windows as a system partition. C:\> bootrec /RebuildBCD Fails with volume does not contain a recognized file system. please make sure that all required file system drivers are loaded and that the volume is not corrupted. So then I attempt to fix the bootsector: C:\> bootsect /nt60 C: /force Which completes successfully (sorry, no output..) Upon rebooting, I have the same problem. I've also tried all of the above after making my Windows partition active: C:\> diskpart DISKPART> select disk 1 DISKPART> select partition 1 DISKPART> active DISKPART> exit Then bootrec as above, both with and without a reboot after the DISKPART commands. Then I've also tried rebuilding the BCD store by hand: set systemdrive=C: set tempbcd=C:\boot\bcd.temp set tempfile=C:\boot\temp.txt bcdedit -createstore %tempbcd% bcdedit.exe -store %tempbcd% -create {bootmgr} -d "Windows Boot Manager" bcdedit -store %tempbcd% -create -d "Windows Vista" -application osloader>%tempfile% set /p winvistaguid= <%tempfile% set winvistaguid=%winvistaguid:~10,38% bcdedit -store %tempbcd% -set %winvistaguid% osdevice partition=%systemdrive% bcdedit -store %tempbcd% -set %winvistaguid% device partition=%systemdrive% bcdedit -store %tempbcd% -set %winvistaguid% path \Windows\system32\winload.exe bcdedit -store %tempbcd% -set %winvistaguid% systemroot \Windows bcdedit -import %tempbcd% However on the import, I get my familiar friendly message: volume does not contain a recognized file system. please make sure that all required file system drivers are loaded and that the volume is not corrupted I'm at my wits end here, and I cannot understand why Windows refuses to see this as a valid install. When I list the disk/partition in DISKPART, it shows up as NTFS and "Healthy", and I can navigate the directory structure from DOS with no problems. I really, really do not want to reformat and reinstall. I know this problem can be solved!

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  • WIndows 7 cannot boot - bootrec reports FS not found or corrupt

    - by purecharger
    For 3 days now I've been unable to boot into my Windows 7 partition, and all my research has been to no avail. I'm hoping someone here has more ideas on how to fix this. When I boot up now, I get the black screen with BCD error that says theres no valid file system or it may be corrupt (pardon my lack of detail, no copy/paste is available then). When I boot with the Windows 7 disc and go into repair tools, no operating system is found, and attempting to automatically repair the problem fails with Unknown Operating System (Unknown Disk) or something similar. When I drop into the command prompt, I am able to see and navigate my C:\ drive without issue. I attempt to use bootrec: C:\> bootrec /ScanOS Finds C:\Windows as a system partition. C:\> bootrec /RebuildBCD Fails with volume does not contain a recognized file system. please make sure that all required file system drivers are loaded and that the volume is not corrupted. So then I attempt to fix the bootsector: C:\> bootsect /nt60 C: /force Which completes successfully (sorry, no output..) Upon rebooting, I have the same problem. I've also tried all of the above after making my Windows partition active: C:\> diskpart DISKPART> select disk 1 DISKPART> select partition 1 DISKPART> active DISKPART> exit Then bootrec as above, both with and without a reboot after the DISKPART commands. Then I've also tried rebuilding the BCD store by hand: set systemdrive=C: set tempbcd=C:\boot\bcd.temp set tempfile=C:\boot\temp.txt bcdedit -createstore %tempbcd% bcdedit.exe -store %tempbcd% -create {bootmgr} -d "Windows Boot Manager" bcdedit -store %tempbcd% -create -d "Windows Vista" -application osloader>%tempfile% set /p winvistaguid= <%tempfile% set winvistaguid=%winvistaguid:~10,38% bcdedit -store %tempbcd% -set %winvistaguid% osdevice partition=%systemdrive% bcdedit -store %tempbcd% -set %winvistaguid% device partition=%systemdrive% bcdedit -store %tempbcd% -set %winvistaguid% path \Windows\system32\winload.exe bcdedit -store %tempbcd% -set %winvistaguid% systemroot \Windows bcdedit -import %tempbcd% However on the import, I get my familiar friendly message: volume does not contain a recognized file system. please make sure that all required file system drivers are loaded and that the volume is not corrupted I'm at my wits end here, and I cannot understand why Windows refuses to see this as a valid install. When I list the disk/partition in DISKPART, it shows up as NTFS and "Healthy", and I can navigate the directory structure from DOS with no problems. I really, really do not want to reformat and reinstall. I know this problem can be solved!

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  • FAT Volume and CE

    - by Kate Moss' Open Space
    Whenever we format a disk volume, it is a good idea to name the label so it will be easier to categorize. To label a volume, we can use LABEL command or UI depends on your preference. Windows CE does provide FAT driver and support various format (FAT12, FAT16,FAT32, ExFAT and TFAT - transaction-safe FAT) and many feature to let you scan and even defrag the volume but not labeling. At any time you format a volume in CE and then mount it on PC, the label is always empty! Of course, you can always label the volume on PC, even it is formatted in CE. So looks like CE does not care about the volume label at all, neither report the label to OS nor changing the label on FAT.So how can we set the volume label in CE? To Answer this question, we need to know how does FAT stores the volume label. Here are some on-line resources are handy for parsing FAT. http://en.wikipedia.org/wiki/File_Allocation_Table http://www.pjrc.com/tech/8051/ide/fat32.html http://www.microsoft.com/whdc/system/platform/firmware/fatgen.mspx You can refer to PUBLIC\COMMON\OAK\DRIVERS\FSD\FATUTIL\MAIN\bootsec.h and dosbpb.h or the above links for the fields we discuss here. The first sector of a FAT Volume (it is not necessary to be the first sector of a disk.) is a FAT boot sector and BPB (BIOS Parameter Block). And at offset 43, bgbsVolumeLabel (or bsVolumeLabel on FAT16) is for storing the volume lable, but note in the spec also indicates "FAT file system drivers should make sure that they update this field when the volume label file in the root directory has its name changed or created.". So we can't just simply update the bgbsVolumeLabel but also need to create a volume lable file in root directory. The volume lable file is not a real file but just a file entry in root directory with zero file lenth and a very special file attribute, ATTR_VOLUME_ID. (defined in public\common\oak\drivers\fsd\fatutil\MAIN\fatutilp.h) Locating and accessing bootsector is quite straight forward, as long as we know the starting sector of a FAT volume, that's it. But where is the root directory? The layout of a typical FAT is like this Boot sector (Volume ID in the figure) followed by Reserved Sectors (1 on FAT12/16 and 32 on FAT32), then FAT chain table(s) (can be 1 or 2), after that is the root directory (FAT12/16 and not shows in the figure) then begining of the File and Directories. In FAT12/16, the root directory is placed right after FAT so it is not hard to caculate the offset in the volume. But in FAT32, this rule is no longer true: the first cluster of the root directory is determined by BGBPB_RootDirStrtClus (or offset 44 in boot sector). Although this field is usually 0x00000002 (it is how CE initial the root directory after formating a volume. Note we should never assume it is always true) which means the first cluster contains data but not like the root directory is contiguous in FAT12/16, it is just like a regular file can be fragmented. So we need to access the root directory (of FAT32) hopping one cluster to another by traversing FAT table. Let's trace the code now. Although the source of FAT driver is not available in CE Shared Source program, but the formatter, Fatutil.dll, is available in public\common\oak\drivers\fsd\fatutil\MAIN\formatdisk.cpp. Be aware the public code only provides formatter for FAT12/16/32 for ExFAT it is still not available. FormatVolumeInternal is the main worker function. With the knowledge here, you should be able the trace the code easily. But I would like to discuss the following code pieces     dwReservedSectors = (fo.dwFatVersion == 32) ? 32 : 1;     dwRootEntries = (fo.dwFatVersion == 32) ? 0 : fo.dwRootEntries; Note the dwReservedSectors is 32 in FAT32 and 1 in FAT12/16. Root Entries is another different mentioned in previous paragraph, 0 for FAT32 (dynamic allocated) and fixed size (usually 512, defined in DEFAULT_ROOT_ENTRIES in public\common\sdk\inc\fatutil.h) And then here   memset(pBootSec->bsVolumeLabel, 0x20, sizeof(pBootSec->bsVolumeLabel)); It sets the Volume Label as empty string. Now let's carry on to the next section - write the root directory.     if (fo.dwFatVersion == 32) {         if (!(fo.dwFlags & FATUTIL_FORMAT_TFAT)) {             dwRootSectors = dwSectorsPerCluster;         }         else {             DIRENTRY    dirEntry;             DWORD       offset;             int               iVolumeNo;             memset(pbBlock, 0, pdi->di_bytes_per_sect);             memset(&dirEntry, 0, sizeof(DIRENTRY));                         dirEntry.de_attr = ATTR_VOLUME_ID;             // the first one is volume label             memcpy(dirEntry.de_name, "TFAT       ", sizeof (dirEntry.de_name));             memcpy(pbBlock, &dirEntry, sizeof(dirEntry));              ...             // Skip the next step of zeroing out clusters             dwCurrentSec += dwSectorsPerCluster;             dwRootSectors = 0;         }     }     // Each new root directory sector needs to be zeroed.     memset(pbBlock, 0, cbSizeBlk);     iRootSec=0;     while ( iRootSec < dwRootSectors) { Basically, the code zero out the each entry in root directory depends on dwRootSectors. In FAT12/16, the dwRootSectors is calculated as the sectors we need for the root entries (512 for most of the case) and in FAT32 it just zero out the one cluster. Please note that, if it is a TFAT volume, it initialize the root directory with special volume label entries for some special purpose. Despite to its unusual initialization process for TFAT, it does provide a example for how to create a volume entry. With some minor modification, we can assign the volume label in FAT formatter and also remember to sync the volume label with bsVolumeLabel or bgbsVolumeLabel in boot sector.

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  • MBR Booting from DOS

    - by eflukx
    For a project I would like to invoke the MBR on the first harddisk directly from DOS. I've written a small assembler program that loads the MBR in memory at 0:7c00h an does a far jump to it. I've put my util on a bootable floppy. The disk (HD0, 0x80) i'm trying to boot has a TrueCrypt boot loader on it. It shows up the TrueCrypt screen, but after typing in the password it crashes the system. When I run my little utlility (w00t.com) on a normal WinXP machine it seams to crash immedealty. Apparently I'm forgetting some crucial stuff the BIOS normally does, my guess is it's something trivial. Can someone with better bare-metal DOS and BIOS experience help me out? Heres my code: .MODEL tiny .386 _TEXT SEGMENT USE16 INCLUDE BootDefs.i ORG 100h start: ; http://vxheavens.com/lib/vbw05.html ; Before DOS has booted the BIOS stores the amount of usable lower memory ; in a word located at 0:413h in memory. We going to erase this value because ; we have booted dos before loading the bootsector, and dos is fat (and ugly). ; fake free memory ;push ds ;push 0 ;pop ds ;mov ax, TC_BOOT_LOADER_SEGMENT / 1024 * 16 + TC_BOOT_MEMORY_REQUIRED ;mov word ptr ds:[413h], ax ;ax = memory in K ;pop ds ;lea si, memory_patched_msg ;call print ;mov ax, cs mov ax, 0 mov es, ax ; read first sector to es:7c00h (== cs:7c00) mov dl, 80h mov cl, 1 mov al, 1 mov bx, 7c00h ;load sector to es:bx call read_sectors lea si, mbr_loaded_msg call print lea si, jmp_to_mbr_msg call print ;Set BIOS default values in environment cli mov dl, 80h ;(drive C) xor ax, ax mov ds, ax mov es, ax mov ss, ax mov sp, 0ffffh sti push es push 7c00h retf ;Jump to MBR code at 0:7c00h ; Print string print: xor bx, bx mov ah, 0eh cld @@: lodsb test al, al jz print_end int 10h jmp @B print_end: ret ; Read sectors of the first cylinder read_sectors: mov ch, 0 ; Cylinder mov dh, 0 ; Head ; DL = drive number passed from BIOS mov ah, 2 int 13h jnc read_ok lea si, disk_error_msg call print read_ok: ret memory_patched_msg db 'Memory patched', 13, 10, 7, 0 mbr_loaded_msg db 'MBR loaded', 13, 10, 7, 0 jmp_to_mbr_msg db 'Jumping to MBR code', 13, 10, 7, 0 disk_error_msg db 'Disk error', 13, 10, 7, 0 _TEXT ENDS END start

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  • How to use BCDEdit to dual boot Windows installations?

    - by Ian Boyd
    What are the bcdedit commands necessary to setup dual boot between different installations of Windows?5 Background i recently installed Windows 8 onto a separate hard drive1. Now that Windows 8 in installed i want to dual-boot back to Windows 7. i have my two2 hard drives: So you can see that i have my two disks, with the partitions containing Windows: Windows 7: \\PhysicalDisk0 (partition 03) Windows 8: \\PhysicalDisk2 (partition 1) What i'm trying to figure out how is how to use bcdedit to instruct the thing that boots Windows that there is another Windows installation out there. Running bcdedit now, it shows current configuration: C:\WINDOWS\system32>bcdedit Windows Boot Manager -------------------- identifier {bootmgr} device partition=\Device\HarddiskVolume2 description Windows Boot Manager locale en-US inherit {globalsettings} integrityservices Enable default {current} resumeobject {ce153eb7-3786-11e2-87c0-e740e123299f} displayorder {current} toolsdisplayorder {memdiag} timeout 30 Windows Boot Loader ------------------- identifier {current} device partition=C: path \WINDOWS\system32\winload.exe description Windows 8 locale en-US inherit {bootloadersettings} recoverysequence {ce153eb9-3786-11e2-87c0-e740e123299f} integrityservices Enable recoveryenabled Yes allowedinmemorysettings 0x15000075 osdevice partition=C: systemroot \WINDOWS resumeobject {ce153eb7-3786-11e2-87c0-e740e123299f} nx OptIn bootmenupolicy Standard hypervisorlaunchtype Auto i cannot find any documentation on the difference between Windows Boot Manager and Windows Boot Loader. Documentation There is some documentation on Bcdedit: Technet: Command Line Reference - Bcdedit Technet: Windows Automated Installation Kit - BCDEdit Command Line Options Whitepaper - BCDEdit Commands for Boot Environment (Word Document) But they don't explain how edit the binary boot configuration data If i had to guess, i would think that a Windows Boot Manager instructs the BIOS what program it should run. That program would give the user a set of boot choices. That leaves Windows Boot Loader do be a particular boot choice, that represents a particular installation of Windows. If that is the case i would need to create a new Windows Boot Loader entry. This means i might want to use the /create parameter: /create Creates a new boot entry: bcdedit [/store filename] /create [id] /d description [/application apptype | /inherit [apptype] | /inherit DEVICE | /device] So i assume a syntax of: >bcdedit /create /d "The old Windows 7" /application osloader Where application can be one of the following types: Apptype Description BOOTSECTOR The boot sector application OSLOADER The Windows boot loader RESUME A resume application Unfortunately, the only documentation about osloader is "The Windows boot loader". i don't see how that can differentiate between Windows 8 on one hard drive, and Windows 7 on another. The other possible parameter when /create a boot loader is >bcdedit /create /D "Windows Vista" /device "The Quick Brown Fox" Unfortunately the documentation is missing for /device: /device Optional. If id is not set to a well-known identifier, the option that is used to specify the new boot entry as an additional device options entry. Since i did not set id to a well-known identifier, i must set /device to "the option that is used to specify the new boot entry as an additional device options entry". i know all those words; they're all English. But i have on idea what it is saying; those words in that order seem nonsensical. So i'm somewhat stymied. i don't want to be like Dan Stolts from Microsoft: I found no content that was particularly helpful when I hosed my machine by playing with BCDEdit. This post would have been ok if there was much more detail especially on the /set command OSDevice, etc. So once I got my machine fixed, I documented the solution and the information is here.... i mean, if a Microsoft guy can't even figure out how to use BCDEdit to edit his BCD, then what chance to i have? Bonus Reading BCDEdit Command-Line Options Bcdedit Server 2008 R2 or Windows 7 System Will NOT Boot After Making Changes To Boot Manager Using BCDEdit Visual BCD Editor4 Windows 7 and Windows 8 RTM Dual Boot Setup Footnotes 1 Since the Windows 8 installer would have damaged my Windows 7 install, i decided to unplug my "main" hard drive during the install. Which is a long-winded explanation of why the Windows 8 installer didn't detect the existing Windows 7 install. Normally the installer would have automatically created the required entries for dual-boot. Not that the reason i'm asking the question is important. 2 Really there's three drives, but the third is just bulk storage. The existence of a 3rd hard drive is irrelevant to the question. i only mention it in case someone wants to know why the screenshot has 3 hard drives when i only mention two. 3 i arbitrarily started numbering partitions at "zero"; not to imply that partitions are numbered starting at zero. i only mention partitions because i don't see how any boot-loader could do its job without knowing which partition, and which folder, an installation of Windows is located in. 4 i'm asking about BCDEdit. i tried Visual BCD Editor. It seems to be a visual BCD editor. That is to say that it's a GUI, but still uses the same terminology as BCDEdit, and requires the same knowledge that BCD doesn't document. 5 For simplicity sake we'll assume that all installation of Windows i want to dual-boot between are Windows Vista or later, making them all compatible with the BCDEdit and the binary boot loader. The alternative would require delving into the intricacies of the old ntloader. Nor am i asking about dual booting to Linux; or how to boot to a Virtual Hard Drive (vhd) image. Just modern versions of Windows on existing hard drives in the same machine. Note: You can ignore everything after the word Background. It's all pointless exposition to satisfy some people's need for "research effort" before they'll consider being helpful. Some people have even been known to summarily close questions unless there is research effort. Some people have been know to close questions if there is too much research effort. Some people close questions when i put the note saying that they can ignore everything after the Background out of spite. Some people are just grumpy.

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  • Help in building an 16 bit os

    - by Barshan Das
    I am trying to build an old 16 bit dos like os. My bootloader code: ; This is not my code. May be of Fritzos. I forgot the source. ORG 7c00h jmp Start drive db 0 msg db " Loader Initialization",0 msg2 db "ACos Loaded",0 print: lodsb cmp al, 0 je end mov ah, 0Eh int 10h jmp print end: ret Start: mov [ drive ], dl ; Get the floppy OS booted from ; Update the segment registers xor ax, ax ; XOR ax mov ds, ax ; Mov AX into DS mov si,msg call print ; Load Kernel. ResetFloppy: mov ax, 0x00 ; Select Floppy Reset BIOS Function mov dl, [ drive ] ; Select the floppy ADos booted from int 13h ; Reset the floppy drive jc ResetFloppy ; If there was a error, try again. ReadFloppy: mov bx, 0x9000 ; Load kernel at 9000h. mov ah, 0x02 ; Load disk data to ES:BX mov al, 17 ; Load two floppy head full's worth of data. mov ch, 0 ; First Cylinder mov cl, 2 ; Start at the 2nd Sector to load the Kernel mov dh, 0 ; Use first floppy head mov dl, [ drive ] ; Load from the drive kernel booted from. int 13h ; Read the floppy disk. jc ReadFloppy ; Error, try again. ; Clear text mode screen mov ax, 3 int 10h ;print starting message mov si,msg2 call print mov ax, 0x0 mov ss, ax mov sp, 0xFFFF jmp 9000h ; This part makes sure the bootsector is 512 bytes. times 510-($-$$) db 0 ;bootable sector signature dw 0xAA55 My example kernel code: asm(".code16\n"); void putchar(char); int main() { putchar('A'); return 0; } void putchar(char val) { asm("movb %0, %%al\n" "movb $0x0E, %%ah\n" "int $0x10\n" : :"r"(val) ) ; } This is how I compile it : nasm -f bin -o ./bin/boot.bin ./source/boot.asm gcc -nostdinc -fno-builtin -I./include -c -o ./bin/kernel.o ./source/kernel.c ld -Ttext=0x9000 -o ./bin/kernel.bin ./bin/kernel.o -e 0x0 dd if=/dev/zero of=./bin/empty.bin bs=1440K count=1 cat ./bin/boot.bin ./bin/kernel.bin ./bin/empty.bin|head -c 1440K > ./bin/os rm ./bin/empty.bin and I run it in virtual machine. When I make the putchar function ( in kernel code ) for constant value ....i.e like this: void putchar() { char val = 'A'; asm("movb %0, %%al\n" "movb $0x0E, %%ah\n" "int $0x10\n" : :"r"(val) ) ; } then it works fine. But when I pass argument to it ( That is in the previous code ) , then it prints a space for any character. What should I do?

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