CentOS 5 :: How Does Grub Stage1 Work
Nov 2, 2009
I have a number of questions about the detailed mechanics of Grub. My first question is hopefully simple. Lets say I have a separate /boot partition at (hd0,0), and install Grub's Stage1 to the MBR. The BIOS knows to load and execute the bootloader residing in (hd0,0)'s MBR because the BIOS is configured in CMOS to do so. But then how does the copy of Stage1 that lives in the MBR know to find Stage2 in the /grub partition of (hd0,0)? If Stage1 was written to the MBR of (hd1) and the grub partition was in (hd1,3) my impression is that Grub handles that seamlessly. I would guess that when Stage1 is copied into the MBR by grub or grub-install, it must have a built-in parameter value that essentially says "find Stage2 at /grub/Stage2 in (hd0,0)". But I haven't found an explanation of this in the Grub manual nor in the webpages I've look at so far.
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May 3, 2010
My Server runs "fine", then I type init 6 for rebooting or some cron job initiates Init 6 and my system stops in grub at: GRUB loading stage1.5. Error 18 After another Ctrl+Alt+Del the system boots as if anything happened. this is why I doubt that it's an issue of too big HDD or BIOS.
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Jan 20, 2010
I successfully installed fedora 12 the other day, got it up and running fine. Yesterday I installed windows 7 on my second partition on the drive (dumbest thing ever, I know). What I forgot is that windows can't handle not being in control, and that it would replace my bootloader (grub). "No problem" I thought. I booted a live usb that had grub-install on it (which has worked for me in the past). The drive which needs grub on it is /dev/sda, sda1 being the partition with /boot on it.
So I do the following in the live usb:
Code:
mkdir /media/fedora
mount /dev/sda1 /media/fedora
grub-install --root-directory=/media/fedora /dev/sda
But after a few seconds I get an error message saying that "stage1 not read correctly". When I go into the drive I can see that there is a file /media/fedora/boot/grub/stage1, and the device.map which grub creates appears to be correct (/dev/sda corresponds to hd0). Going into the grub terminal and running "root (hd0,0)" then "setup" gives a similar result (complains about not being able to find stage1).
On another forum someone mentioned tyring "depmod" before installing grub, but that didn't work for me.
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Jan 12, 2011
Hi All,
I am using legacy grub(0.9.7) as my boot loader. I want to add some code into GRUB stage1. But I am getting following error.
stage1.S: Assembler messages:
stage1.S:591: Error: attempt to move .org backwards
stage1.S:603: Error: attempt to move .org backwards
make[2]: *** [stage1.o] Error 1
It seems like Stage1 code is starting after BPB only. Is it possible to use BPB section for GRUB stage1 (GRUB is installed in HDD)??
If yes, how to change the code start to BPB section??
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Mar 11, 2010
Due to lack of concentration, I inadvertantly ran PClinux(2009-2)'s "install.sh" while I was in openSuse 11.1. This file says:
grub --device-map=/boot/grub/device.map --batch <<EOF
root (hd0,6)
setup --stage2=/boot/grub/stage2 (hd0,6)
quit
EOF
I soon found out that Suse 11.1 would no longer boot from boot.ini (using bootpart) because the boot process now brings up PCLOS (in /dev/sda6) rather than Suse 11.1 sitting in /dev/sda5. No problem, I thought, I'll boot from the Suse install DVD, use repair, and away I go. Wrong. After grinding, it started mentioning about generating something for sda13, which is my last partition. NTFS! So I bailed before it got too far. I even tried "rescue" option on the DVD, command prompt, and grub commands to reinstall via "setup.
Then I tried to use Super Grub Disk (.97xx) to reinstall the PBR, stage 1 and stage 2 loaders. Didn't change a thing. So then I used Grub4DOS and got into my Suse 11.1 installation using this in its menu.lst:
title openSUSE 11.1 - 2.6.27.45-0.1
[Code]...
Worked fine, and is now my (only) method of booting to 11.1. So obviously it's bypassing stage 1 and 2 files, using it's native Grub4DOS code. But then I tried Yast-Bootloader to reinstall Grub's files. No difference. Then I used the advanced part to "write bootloader code to disk" No difference. Even tried "propose a new boot scheme" (or whatnot) no difference. After looking at all this, I've come to the conclusion that the PBR code in sda5 is scraunched, and/or stage 1 code (although it's still the original date), or stage 2 (which definitely had a new timestamp of when I committed the fatal error by executing PCLOS's "install.sh".
So my question is this: How do I do a good COMPLETE re-install of Suse's version of the grub files? Because, for sure, grub commands like "setup --stage2=/boot/grub/stage2 (hd0,5), and variations thereof, certainly aren't doing it? My reasoning is that I should make sure that all the boot files get restored/confirmed as "originally installed by Suse".
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Jul 10, 2010
What does stage1 and stage2 refer to in grub folder.
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Jun 28, 2010
i am newer to linux.i have a doubt in linux boot process in my machine RHEL5 has installed,in bootig GRUB will load in 3 steps
stage 1--> stage1.5 --->stage2
stage1
1st stage1 of grub is located in the 412 bytes of MBR)
also there is a file
/boot/grub/stage1 ( then what is this???)
stage1.5
( where does stage1.5 file located ? i found certain files in /boot/grub/)
like
e2fs_stage1_5
fat_stage1_5
ffs_stage1_5
code....
but my qusetn is GRUB loads from among these files??i removed the above mentioned files from /boot/grub ,but my system is still booting!!!!!!!!!!!!!!!!!!
how it is?then how stage1.5 and stage2 take place??
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May 23, 2010
When I try and boot my Debian computer I get the messages: Grub Loading stage1.5. Grub loading, please wait... Error 15 Is there any way of recovering from this - or is it simply a fresh install? I was attempting an upgrade from Lenny to Squeeze and despite a few hurdles it looked like it was all happening. Got the new kernel loading, and the new grub. It looked as though grub2 was working so I ran the grub-remove-legacy-support command (something like that) and now my computer won't boot grub or Linux.
I'm assuming the MBR on my harddrive is lost, however I don't know what state the partition is in. I'm guessing that maybe this has been lost as well. I tried a few tools from the Ultimate Boot CD but nothing here was able to re-install my grub or boot from any partition or even mount my file-system. I'm fearing the worst but would like it confirmed before I blow it all away with a new install.
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Mar 31, 2010
I have a system that we ghosted with SGS 2.0.1 (Ghost 11).We ghosted the whole disk, but when we send it out - we plan to be able to restore individual partitions. mainly because it is running VMware server 2, and the partition restores will allow the admins to restore Individual VMs by restoring their partitions - OR - leave the VMs alone and restore just the Red Hat Linux root partition if they mess something up.
Unfortunately, this didn't work correctly right away. When restoring the root partition by itself, the system hangs on the word GRUB.Using the Rescue Disk we can get it running again. Then, after re-ghosting- and then restoring the new ghost partition - it works!I thought it was because we added the "-IB" switch to the ghost executable. This includes the boot info into the image. But maybe it was the rescue disk all along.
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Dec 24, 2010
I have installed ubuntu and Centos 5 , but when i do sudo update-grub , the new centos 5 is not detected. Some days ago i did the same (i installed ubuntu , and then Centos 5) , but i had to format the hard disk because some problems i had. The thing is that in that first time update-grub worked , but now not , why? Shouldn't be detected this time too? I have to manually add the new entry to the grub no?
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Jun 4, 2011
So I have 2 ide hdds but whenever they are both connected, grub gets stuck at GRUB loading stage 1.5. how can I resolve this problem?
both are Maxtors with ext4 fs. primary is 20 gb and secondary 80 gb.
Jumpers are set to cable select.
Boot order in bios is correct. (primary first, secondary isn't in the list at all)
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Mar 4, 2011
I have 2 hard disks. sda,sdb
In sda, I have 4 partitions, and I have windows 7 in one of the extended partitions [not in the primary partition].
In sdb, I have 3 partitions. 2 for storage, and 1 10GB drive for Ubuntu. Again, Ubuntu is not of a primary partition.
I had ubuntu 10.04 running on that for a long time. However, I wanted to reinstall ubuntu and use 10.10.This is what I did EXACTLY:Booted from Ubuntu install CD
Chose advanced istall
Selected sdb3 for Ubuntu
I installed GRUB2 on the SAME partition as Ubuntu aka sdb3 Installed then rebooted
I can boot into Ubuntu fine, but whenever I select Windows 7 bootloader from the GRUB menu, the screen goes black, and my PC reboots.
Boot Info:
Code:
Boot Info Script 0.55 dated February 15th, 2010 [code]....
ls: reading directory sda6/: Input/output error
I have tried the testdisk/update-grub method, but it didn't work.
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Mar 21, 2011
I have used CentOS for a while and have never run into this issue. I searched all over and didn't see a similar issue anywhere, I did an install of CentOS as a server (no GUI) with only the base. Partition is /boot ext3, size of 100MB. The rest of the drive is partitioned as / with ext3. This is being done on a CompactFlash card of 32GB in size. The BIOS sees it as an IDE drive.
When the install completes and the system reboots, the grub stops at the grub> prompt. There is no menu for OS options. If I do the following commands:
grub>root (hd0,0)
grub>kernel /vmlinuz-2.6.18-194.el5 root=LABEL=/
grub>initrd /initrd-2.6.18-194.el5.img
grub>boot
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Jun 23, 2010
Ubuntu 10.04 was in small slave-disk, and I put other bigger disk same type IDE/ATA.In first start I get message: "no such device....., grub rescue."Anyway, I make installation in this disk and and now after start message is: "error: out of disk, grub rescue.So now I can not use master/XP and no slave/Ubuntu.
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May 5, 2009
I'm trying to install a dual booting machine with OpenSUSE v11.1 32bit and CentOS v5.2 64bit. I installed OpenSUSE first and allowed it to install and configure grub in the MBR and after that I wanted to proceed with CentOS v5.2. The installation went fine with two notable exceptions:- when I had to configure grub installation parameters, CentOS offered me only 2 solutions: either install it on the MBR of the first hard disk or not installing it at all. Other distributions are more flexible allowing you to install it in the boot sector of the root partition for example. Because I didn't want to ruin the existent grub onfiguration, I reluctantly accepted not to install it for CentOS assuming that I could manually configure the entry later in grub's menu.lst file.
- when I was presented with the options for software components installation, I've clicked on virtualization category/function because I intend to use the machine as a VMware host. There was no guidance on screen at that point and I blindly assumed that by choosing the virtualization function I would get necessary tools and drivers that will help me further on. It seems that this was a wrong move as you can see it below.
After completing the installation, I tried to search for a template or guiding on how the menu entry in menu.lst should look like but the grub directory was empty, not surprisingly because I've told CentOS earlier not to install it. Using the files in the /boot directory from the CentOS installation I tried to improvise a menu entry but it's not working. The boot stops with famous Error 13: Invalid or unsupported executable format. Using the file command to check what kind of files I'm trying to load as kernels I'm getting :
marte:~ # file /mnt/vmlinuz-2.6.18-92.el5xen
/mnt/vmlinuz-2.6.18-92.el5xen: gzip compressed data, from Unix, last modified: Tue Jun 10 19:20:51 2008, max compression
[code]....
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Nov 10, 2009
I just upgraded by box from Fedora Core 9 to Centos 5.2. Finally!I have a 500GB SATA drive, it's partitioned into three equal size slices, hda1 through 3. The old Fedora was on hda1, I installed the new Centos on hda3. I instructed the installer to write the MBR to /dev/hda, not /dev/hda3. Fdisk says I have sector 0 unused.First, the system wouldn't boot - it just looped through the BIOS, rebooting over and over again. The BIOS sees the disk, but it never loaded Grub. I tried re-running grub-install /dev/hda, and not I get a Grub Error 17 after stage 1.5 loads.
I can boot from rescue OK, the grub.conf man menu.lst look fine, it's pointing to "root (hd0,2)". It's either the BIOS that can't find the MBR, or the MBR can't find Grub.When I looked at the disk with fdisk after the install, hda1 was still marked bootable, hda3 was not, so I swapped bootable flags but that has not made a difference. I also appended the new grub to the old grub thinking I could get the MBR (if it is there) to load the old grub and thence find the new Centos, but that didn't work either.Mobo is an old Shuttle AK35.Any ideas? Did I mess up by not telling the system to put the MBR on /dev/hda3? Is there a way to fix this without reinstalling?
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Feb 22, 2011
Ive installed centos freebsd and mandriva but i want to manage grub from my centos and y create successfully a boot load for freebds. But for mandriva it just doesnt work... so how can a create a boot load entry for mandriva from grub centos?
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Sep 19, 2010
3 partitions (in order): Windows 7, CentOS and shared data partition.
I need to increase the size of the Windows 7 partition (c:windowswinsxs seems to be something not easily remedied).
GParted didn't work in moving things around (bad sector) so I wiped out its partition (# 2 out of 3) and I was able to increase the size of the Windows 7 partition (I can reinstall CentOS easily and not much work lost).
Except ... no more grub menu (unsurprising). This incantation does allow me to boot into Windows 7.
Is there any way of rebuilding the grub menu short of reinstalling CentOS (5.5)?
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Jan 12, 2011
I am trying to set up an unused machine as a web server for my students.
I originaly tried with Redhat 9 and had the same problems. I am using an HP Pentium 4 system with 2 network cards.
1) The built in Realtek RTL8139 configured as eth0.
2) An add in Broadcom BCM5782 Gigabit card that was added I presume when the built in card failed (we have a number of machines like this around the school), configured as eth1.
I did not realize the second card was installed when I had Red hat 9 on the system, but I discovered it after installing centos 5.5. I have tried to configure the system to use DHCP with and without getting the DNS from the provider, and both ways the system complains that there is no connection, check the cable, so it will not activate the device.
When I configure the device to use a fixed IP, I can configure the device, but I can't ping anything on the network other than myself. I suppose it is possible that both network cards have failed, but I get green link lights with both cards, when I connect them to my router, so I am at a loss as to why neither board seems to work. I don't have a spare network card to slide in because the computer takes a special mini card. Is there an easy way to test the board to see if the board is a problem?
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Apr 15, 2010
pulled up an old clunker and put centos 5.4 on it the other day. well the grub spash screen appears but i have to manually hit enter to select a kernel.at the /boot/grub/grub.conf file and timeout=5. this is a new install. so I tried changing that value to 0 and it does boot the kernel immediately but never displays the splash screen. so something is not right I assume. btw I see a message (loading stage 2) for about 20 seconds as the computer boots and I have never seen that message on my ubuntu machine, so I wonder if something is off there.
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Jul 1, 2010
I installed following this guide but not install a boot loader, because only use this disk (hdd) with centosAfter the installation, restart and I have the following message "missing operating system"any suggestions to solve this problem?or centos can not install without grub?
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Jan 27, 2009
I have a Centos 5.2 VM running under Windows 2008 Hyper-V. If I add two "legacy Nic's" and bridge them, everything appears to work fine. However, if I remove the legacy nics and replace them with two synthetic nics (linux integration components), the nics seems to function fine UNTIL I add them to a bridge.This VM will eventually be used as a DansGuardian/Squid transparent proxy for a local library. The logical layout is represented by the attached jpg image. I have also included the ifcfg- scripts for the adapters and bridge for both scenarios.It would also be useful if someone else has Hyper-V with the integration components and dual physical nics to see if they can reproduce my symptoms on their box.Legacy Adapters:
ifcfg-br0:
DEVICE=br0
BOOTPROTO=dhcp
[code]....
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May 1, 2009
I just have CentOS installed and cannot get the Agere et131x network card to work.I have tried the following:Reboot the computer and still did not see the network hardware.
Fai
lspci
Quote:
[code]....
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Jun 27, 2009
This will be a little long (having read Phil's 'how to ask questions' FAQ). I'm trying to get OpenVPN working between my CentOS server and some Windoze laptops running XP. There seems to be plenty of sample
config files available, but to date, none of them have worked for me. Pulling out my trusty Wireshark, I've found some clues,
BACKGROUND:
My local subnet (NAT'ed by my gateway router) is 192.168.52.x. My router has been configured with a conduit (port-forward) for port 1194 (the standard OpenVPN port), which points towards my CentOS server.The CentOS server is .52.112, and the supplicant is .52.110. I have tried the lient both inside and outside my local subnet, with no difference in events or outcomes.
[Code]...
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Jun 25, 2011
i have a centos 5 and i cant access to the LAN or Internet because , i cant create a network connection , i try to say My Ethernet dont appears,and i cant add any connections.i id thisTerminal:Quote:sudo iwconfig
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Dec 17, 2009
I`m looking for a a X-Window in CentOS. At the moment I work with console only in text mode
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Dec 19, 2009
I am eager to install GSN3 on CentOS 5 and work on GNS3. But i am unable to find a suitable easy guide to install the same. install GSN3 on CentOS.5 with rpm links if you suggest to download.
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Jul 4, 2010
i like to use my DVB-C Card KNC-One on Centos 5.5 x86_64. But i cant get it to work. on a 32 Bit Centos this is working like a charm. I tryed several different kernels together with the video4linux-kmdl
At the moment i am using this kernel: 2.6.18-194.3.1.el5.centos.plus
[Code]....
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Aug 10, 2010
where to find ODBC drivers for CentOS 5.5 to work with Perl 5.x (preferrably free)?
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Nov 29, 2009
By the way, is there a step by step guide to install XFS file system and other related components on CENTOS 5.3,
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