Home
Main website
Display Sidebar
Hide Ads
Recent Changes
View Source:
GrubNotes
Edit
PageHistory
Diff
Info
LikePages
!! Grub 2, what's the deal? Grub got a rewrite recently and inherently became a lot more powerful. However you may be wondering where the old menu.lst file has run off to. menu.lst (on debian at least) has been replaced by a series of scripts which build a grub.cfg (grub 2 config file) for you. Things you probably care about: ! How do I change kernel options? Simply edit /etc/default/grub then run update-grub ! How do I add other OSs Generally installing os-prober will solve this problem. <pre> aptitude install os-prober os-prober update-grub </pre> you should see it spit out some info about adding your other OSs ! I want to add a new boot section to grub manually Simply edit /etc/grub.d/40_custom and add the new section. This will be copied to /boot/grub/grub.cfg when you run update-grub next. !! I need to reinstall grub in my master boot record Boot off a liveCD, and [chroot(8)] into your main root partition. __Remember that grub numbering starts at 0:__ __/dev/hda1__ becomes __(hd0,0)__, etc. However, note that GRUB’s disk ordering is determined by the BIOS, while the Linux kernel’s ordering is not. For instance, on an Asus Eee 701, if you change the BIOS boot order to put the SD-card slot ahead of the internal SSD, GRUB will swap their names around so the internal SSD becomes “hd1” and the SD-card becomes “hd0”. However, the kernel will still call them “sda” and “sdb” respectively. Run 'grub'. Issue =root (hdx,x)= if you know where your __/boot__ directory is, or use =find /boot/grub/stage1= to find it if you don't. Then issue =setup (hdx)= to install GRUB in the master boot record of drive hdx, or =setup (hdx,x)= to setup inside a partition. Alternatively on many modern distros you can use [grub-install(8)] to do this e.g. grub-install /dev/hda !! I get "The file /boot/grub/stage1 not read correctly" when running <tt>grub-install</tt> Even if you can see the file /boot/grub/stage1 on your filesystem, this error message means that grub can't find it when it is running. Grub consults your /etc/fstab and /etc/mtab files to determine which partition/drive the '''/boot''' directory is actually on, so check those files are correct. (See the next section for more details about this.) There are also lots of other obscure reasons why it can't be found, and unfortunately the GRUB developers don't believe in giving users better error messages. In my case, I got this because I was trying to install an MBR to boot of a drive that had linux installed on a partition that used to have windows xp. In this case, the partition type was set to "NTFS" despite containing an ext3 partition. Using ''cfdisk'' to change the partition type to be "83 (linux)" meant that when I next ran __grub-update__, it worked. !! I get "Error 15" on boot even after reinstalling GRUB from a rescue CD This one had us stumped for a while, until I noticed that the boot order in BIOS was CDROM -> IDE-1 -> Floppy. The correct device should have been IDE-0. IDE-1 is the Primary SLAVE drive which in this case happened to exist, and also happened to have an old copy of GRUB on the MBR. Sometimes the problem isn't where you expect it to be! !! I get a grub> prompt on boot This means [GRUB] can't find your config file. You can still boot into the system by issuing appropriate commands. Eg., if I have a system which has a single disk, partitioned with __/dev/hda1__ as __/boot__ and __/dev/hda5__ as __/root__, and I have a [Kernel] called __vmlinuz__ in __/boot__, I can do: <pre> root (hd0,0) kernel /vmlinuz root=/dev/hda5 ro boot </pre> and it'll boot quite happily -- this time. Note that I set the [GRUB] root to __(hd0,0)__, which corresponds to __/dev/hda1__, and so the path to the kernel is relative to the top of __/dev/hda1__ (which is __/boot__ when mounted correctly). Also note that the [GRUB] shell features tab completion on filenames, so you can do __kernel /~[tab]__ and get a list of possible values. You can also use this to work out which [FileSystem]s are which, as [GRUB] will understand most [Linux] [FileSystem]s you're likely to have. However, the real problem is that [GRUB] can't find your config file. First, check that you have one - it should be in __/boot/grub/menu.lst__ by default, but some distributions put it at __/boot/grub/grub.conf__. If the latter is the case, make a symlink between the two and reboot to test: =ln -s /boot/grub/grub.conf /boot/grub/menu.lst= If that still doesn't work, it's possible that [GRUB] is looking in the wrong place for your config. If you installed [GRUB] using something like =grub-install --root-device=/boot '(hd0)'= it will install to __/boot/grub/__ etc, however if your __/boot__ is on a separate partition (as I described in the example above) then it's fairly likely that [GRUB] is looking in __/boot/boot/grub/__ for __menu.lst__ -- and not finding it. Easiest fix (it stops this happening again in the future, so perhaps the best fix?) is to symlink __/boot__ into __/boot__ by doing =ln -s /boot /boot/=. You should now be able to cd into __/boot/boot/grub__ and it'll have your __menu.lst__ there. !! Adding a new kernel to grub If you're building your own kernels or doing KernelDevelopment then you need to manually edit the files for [grub(8)] or on many distros you can run [update-grub(8)]. One thing to note is that if you rearrange hard drives you need to edit the menu.lst file to tell it which drive is which and the kernel options before running [update-grub(8)]. The lines needed have a hash symbol in front of them which makes them look like a comment only, but they are not a comment at all!! !! Using a different kernel for the next reboot only <pre> grub savedefault --default=N --once ''(where N is the number of the kernel you want to boot once)'' quit </pre> Reboot your machine. It will boot using kernel "N". =grub-reboot N= will do essentially the same thing and prompt to reboot the machine !! Using [GRUB] with a serial console In the [GRUB] config file (normally /boot/grub/menu.lst) add these lines to the top to enable the serial console in addition to the regular console: <pre> serial --unit=0 --speed=9600 terminal --timeout=10 serial console </pre> [GRUB] will now display on the serial console as well as locally. It will wait for a keypress for 10 seconds to determine which input is being used, before timing out and carrying on the boot process. If a key is pressed then the regular menu will be displayed and you can select a kernel as usual. The first line configures the serial link with the following options (defaults to 9600, 8n1 from what I can gather): * ''--unit=X'' which serial port to use. 0 = ttyS0, 1 = ttyS1 etc * ''--speed=X'' the rate in bps the serial link should run at * ''--word=X'' number of data bits * ''--parity=X'' parity to use, where X is one of 'no', 'even', 'odd' * ''--stop=X'' number of stop bits to use The second line specifies which devices should be used for input/output. You can set it up so that it only displays locally, only on the serial console, or on both. * ''--timeout=X'' the number of seconds [GRUB] should wait for a keypress before continuing * ''serial'' if this option is present, the serial console will be used * ''console'' if this option is present, the local console will be used If both ''serial'' and ''console'' are present, then grub will use whichever method accepts a keypress first ! Making your kernel do serial too! If you have [GRUB] setup to use a serial console then you probably want to compile your kernel with serial console support and append the following options to your boot line, so your kernel messages appear on your serial console too. If you don't do this you'll have a big empty screen between grub loading the kernel and your getty loading, when you think that your kernel has hung! =console=ttyS0,19200n8= So a full kernel boot line might look like =kernel /boot/vmlinuz ro root~=/dev/hda1 console=tty0 console=ttyS0,19200n8= ---- !! GRUB resources on the web * [GRUB homepage | http://www.gnu.org/software/grub] * [GRUB manual | http://www.gnu.org/software/grub/manual/html_node/] * [GRUB wiki | http://grub.enbug.org/] * [Linux+Win+GRUB HowTo | http://tldp.org/HOWTO/Linux+Win9x+Grub-HOWTO/index.html] * [Linux Recovery and Boot Disk Creation with GRUB | http://promote-opensource.org/modules/mylinks/singlelink.php?cid=14&lid=94] * [Win32 GRUB | http://www.skyjammer.com/files/knoppix/] * [Booting with GRUB | http://www.ameritech.net/users/gholmer/booting.html] * [WinGRUB | http://grub4dos.sourceforge.net/] * [GRUB installer for Windows | http://www.geocities.com/lode_leroy/grubinstall/] * [GRUB for DOS | http://grub.linuxeden.com/] - Bridging DOS/Windows to Unix/Linux * [Comparison of GRUB and LILO|http://www-128.ibm.com/developerworks/library/l-bootload.html?ca=dgr-lnxw01LILOandGRUB] * [GRUB FAQ | http://www.gnu.org/software/grub/grub-faq.en.html] * [GRUB Manual | http://www.gnu.org/software/grub/manual/html_node/] * [GRUB wiki | http://autistici.org/grub/] * [Linux+Win9x+Grub HOWTO | http://www.tldp.org/HOWTO/Linux+Win9x+Grub-HOWTO/] * [Multiboot with GRUB Mini-HOWTO | http://www.tldp.org/HOWTO/Multiboot-with-GRUB.html] * [APC guide to dual-booting Vista/XP/Linux | http://apcmag.com/5162/the_definitive_dual_booting_guide_linux_vista_and_xp ]
2 pages link to
GrubNotes
:
GRUB
TroubleshootingStartUp
