Consulteu també l'article GRUB que fa referència a GRUb v1 però que conté també informació important i que és comuna a les dos versions.
La principal novetat de la versió 2 és que permet uns menús d'arrancada completament gràfics.
Paquets instal·lat en una Ubuntu Jaunty (9.04):
$ dpkg -l | grep grub ii grub 0.97-29ubuntu53 GRand Unified Bootloader ii grub-common 1.96+20080724-12ubuntu2 GRand Unified Bootloader, version 2 (common
Les fases per les que passa el procés d'arrancada amb GRUB són:
$ ls -la /boot/grub/*img -rw-r--r-- 1 root root 512 2010-12-27 09:17 /boot/grub/boot.img -rw-r--r-- 1 root root 512 2010-12-27 09:17 /boot/grub/cdboot.img -rw-r--r-- 1 root root 23817 2010-12-27 09:17 /boot/grub/core.img -rw-r--r-- 1 root root 512 2010-12-27 09:17 /boot/grub/diskboot.img -rw-r--r-- 1 root root 10240 2010-12-27 09:17 /boot/grub/grldr.img -rw-r--r-- 1 root root 29028 2010-12-27 09:17 /boot/grub/kernel.img -rw-r--r-- 1 root root 1024 2010-12-27 09:17 /boot/grub/lnxboot.img -rw-r--r-- 1 root root 1024 2010-12-27 09:17 /boot/grub/pxeboot.img
El sistema és més flexible, si us fixeu per exemple es pot precarregar la imatge pxeboot.img abans de la core.img per tal de tenir suport per a xarxa.
Sembla que ja vindrà instal·lat per defecte
Per instal·lar
$ sudo apt-get install grub2
Apareixerà el següent missatge:
Que ens indica que GRUB 2 ha trobat fitxers antics de GRUB i ens recomanen que el GRUB 2 que instal·lem s'executi des de GRUB 1 mitjançant Chain Loading (és a dir tenir GRUB 1 i GRUB 2 al mateix temps conservant el GRUB 1 al MBR). Un cop comprovem que el GRUB 2 instal·lat és correcte se'ns indica que podrem passar GRUB 2 al MBR amb la comanda:
upgrade-from-grub-legacy
El Chain Loading el farà automàticament l'instal·lador.
Ara us mostrarà un missatge sobre les opcions del kernel. Accepteu:
Ara podeu provar el nou GRUB tornant a iniciar la màquina:
$ sudo reboot
Durant la càrrega estigueu atents per entrar al menú de GRUB (amb ESC) i trobareu una nova entrada:
Si us dona l'error:
Error 11: Unrecognized device String
Seguiu les passes deError 11: Unrecognized device String per solucionar el problema. El resultat serà quelcom similar a:
Si voleu fer els canvis permanents, inicieu el sistema i executeu:
$ sudo upgrade-from-grub-legacy Installing GRUB to Master Boot Record of your first hard drive ... Installation finished. No error reported. This is the contents of the device map /boot/grub/device.map. Check if this is correct or not. If any of the lines is incorrect, fix it and re-run the script `grub-install'. (hd0) /dev/sda GRUB Legacy has been removed, but its configuration files have been preserved, since this script cannot determine if they contain valuable information. If you would like to remove the configuration files as well, use the following command: rm -f /boot/grub/menu.lst*
A la versió 1.96 encara no esta suportat. Ho estarà per la Karmic?
Vegeu:
http://grub.gibibit.com/
Hi ha canvis respecte Grub 1...
Exemples:
Consulteu també la notació de Grub 1 (Grub legacy) Grub#Notaci.C3.B3_Grub
Els trobareu a la carpeta /boot/grub. Com que el MBR és molt petit com per contenir tots els mòduls de Grub 2, només el menú i algunes comandes molt bàsiques es troben al MBR. La gran part de la funcionalitat de GRUB2 es troba a /boot/grub en forma de mòduls (fitxer amb l'extensió .mod) i són inserits a mesura que és necessiten amb l'ordre insmod.
$ ls 915resolution.mod cpuid.mod gcry_crc.mod help.mod multiboot2.mod raid5rec.mod ufs2.mod acpi.mod crc.mod gcry_des.mod hexdump.mod multiboot.mod raid6rec.mod uhci.mod affs.mod crypto.lst gcry_md4.mod hfs.mod nilfs2.mod raid.mod usb_keyboard.mod afs_be.mod crypto.mod gcry_md5.mod hfsplus.mod normal.mod read.mod usb.mod afs.mod cs5536.mod gcry_rfc2268.mod iorw.mod ntfscomp.mod reboot.mod usbms.mod aout.mod datehook.mod gcry_rijndael.mod iso9660.mod ntfs.mod regexp.mod usbtest.mod ata.mod date.mod gcry_rmd160.mod jfs.mod ohci.mod reiserfs.mod vbeinfo.mod ata_pthru.mod datetime.mod gcry_seed.mod jpeg.mod part_acorn.mod relocator.mod vbe.mod at_keyboard.mod diskboot.img gcry_serpent.mod kernel.img part_amiga.mod scsi.mod vbetest.mod befs_be.mod dm_nv.mod gcry_sha1.mod keystatus.mod part_apple.mod search_fs_file.mod vga.mod befs.mod drivemap.mod gcry_sha256.mod linux16.mod part_bsd.mod search_fs_uuid.mod vga_text.mod biosdisk.mod echo.mod gcry_sha512.mod linux.mod part_gpt.mod search_label.mod video_bochs.mod bitmap.mod efiemu32.o gcry_tiger.mod lnxboot.img partmap.lst search.mod video_cirrus.mod bitmap_scale.mod efiemu64.o gcry_twofish.mod loadenv.mod part_msdos.mod serial.mod video_fb.mod blocklist.mod efiemu.mod gcry_whirlpool.mod locale part_sun.mod setjmp.mod video.lst boot.img elf.mod gettext.mod loopback.mod part_sunpc.mod setpci.mod video.mod boot.mod example_functional_test.mod gfxmenu.mod lsmmap.mod parttool.lst sfs.mod videotest.mod bsd.mod ext2.mod gfxterm.mod ls.mod parttool.mod sleep.mod xfs.mod bufio.mod extcmd.mod gptsync.mod lspci.mod password.mod tar.mod xnu.mod cat.mod fat.mod grldr.img lvm.mod password_pbkdf2.mod terminal.lst xnu_uuid.mod cdboot.img font.mod grub.cfg mdraid.mod pbkdf2.mod terminal.mod zfsinfo.mod chain.mod fshelp.mod grubenv memdisk.mod pci.mod terminfo.mod zfs.mod cmostest.mod fs.lst gzio.mod memrw.mod play.mod test.mod cmp.mod functional_test.mod halt.mod minicmd.mod png.mod tga.mod command.lst gcry_arcfour.mod handler.lst minix.mod probe.mod trig.mod configfile.mod gcry_blowfish.mod hashsum.mod mmap.mod pxeboot.img true.mod core.img gcry_camellia.mod hdparm.mod moddep.lst pxecmd.mod udf.mod cpio.mod gcry_cast5.mod hello.mod msdospart.mod pxe.mod ufs1.mod
Un dels mòduls més importants és linux.mod que té el suport per a les ordres initrd i linux. Consulteu l'apartat Grub shell per a més informació.
http://www.linux.com/learn/tutorials/776643-how-to-rescue-a-non-booting-grub-2-on-linux/
Cal tenir en compte que respecte a Grub 1 (Grub legacy) moltes ordres han canviat de sintaxi.
Com que el MBR és molt petit com per contenir tots els mòduls de Grub 2, només el menú i algunes comandes molt bàsiques es troben al MBR. La gran part de la funcionalitat de GRUB2 es troba a /boot/grub en forma de mòduls (fitxer amb l'extensió .mod) i són inserits a mesura que és necessiten.
La consola de Grub (Grub shell) apareix quan hi ha problemes.
Hi ha diferents consoles de shell, per exemple si us surt:
grub rescue>
Amb l'ordre:
grub rescue> set
Podeu veure com estan configurades les variables.
És un conjunt restringit de la shell normal, per intentar activar la shell "normal" de Grub:
grub rescue> set prefix=(hdX,Y)/boot/grub grub rescue> insmod (hdX,Y)/boot/grub/normal.mod
NOTA: Vigileu que no tots els casos són iguals! Per exemple si la partició boot està separada (Proxmox, Ubuntu Server, sistemes amb LVM, etc aleshores:)
grub rescue> set prefix=(hdX,Y)/grub
Per saber les particions possibles escriviu ls i tabuleu dos cops
grub rescue> ls TABULEU
Si no apareixen particions LVM cal activar el mòdul LVM
grub rescue> insmod lvm
Ara:
rescue:grub> normal
Amb normal passem a la següent fase de grub que seria mostra el menú de boot típic de GRUB.
sh:grub>
En aquest últim cas vegeu com ha canviat el PROMPT, aquest prompt és el prompt de shell normal.
Anem a veure ara com es pot fer una arrencada "normal" amb ordres de Grub:
Algunes de les ordres disponibles a GRUB rescue són:
"insmod", "ls", "set" i "unset"
L'ordre ls us mostrarà les particions detectades.
El primer que cal saber és on està la partició que conté la carpeta /boot
grub rescue> set prefix=(hdX,Y)/boot/grub
on X és el número de disc físic i Y és el número de partició. Tingueu en compte que la notació de Grub 2 (GRUB_2#Notaci.C3.B3_de_Grub_2) és diferent que la de Grub 1,
Per exemple:
grub rescue> set prefix=(hd0,0)/boot/grub
Correspon a la primera partició del primer disc dur. El següent pas és inserir el modul de linux per tenir més comandes disponibles:
grub rescue> insmod (hdX,Y)/boot/grub/linux.mod
o simplement
grub rescue> insmod linu
nota: Si /boot està a una partició a part cal ometre el prefix /boot: prefix=(hdX,Y)/grub i insmod (hdX,Y)/grub/linux.mod).
Ara teniu disponibles les ordres "linux" i "initrd" que són similars a les disponibles a Grub 1, per arrancar una sistema Linux:
set root=(hd0,5) linux /boot/vmlinuz26 root=/dev/sda5 initrd /boot/kernel26.img boot
IMPORTANT: Noteu com ara root no és un ordre sinó una variable que s'estableix amb l'ordre set
Per activar el suport de paginació:
sh:grub> set pager=1
Podeu consultar també GRUB#GRUB_Shell.
Resum dels canvis:
TODO:
find is replaced with search geometry is gone and replaced by ls kernel (in menu.lst) is replaced by linux (and other terms for different OSs) title (in menu.lst) is replaced by menuentry (in grub.cfg) root is still used but is now a variable setup is gone; the work is done by grub-install map is replaced by drivemap device is replaced by loopback (makes a drive out of a file) set is a GRUB 2 term used to set a variable
Podeu instal·lar imatges splash amb:
$ sudo apt-get install grub2-splashimages
Ara les imatges es troben a:
/usr/share/images/grub/
Les podeu copiar a la carpeta de GRUB amb:
$ sudo cp /usr/share/images/grub/*.tga /boot/grub/
A:
http://members.iinet.net/~herman546/p20/GRUB2%20Splashimages.html
Trobareu thumbnails de les imatges.
Per utilitzar-les cal editar el fitxer
$ gksu gedit /etc/grub.d/05_debian_theme
Busqueu la línia:
Acacha Wikifor i in {/boot/grub,/usr/share/images/desktop-base}/moreblue-orbit-grub.{png,tga} ; do
I canvieu-la per
for i in {/boot/grub,/usr/share/images/desktop-base}/Windbuchencom.{png,tga} ; do
On Windbuchencom és la imatge escollida. Ara executeu:
$ sudo grub-mkconfig Updating /boot/grub/grub.cfg … Found Debian background: Windbuchencom.tga Found linux image: /boot/vmlinuz-2.6.27-7-generic Found initrd image: /boot/initrd.img-2.6.27-7-generic Found memtest86+ image: /boot/memtest86+.bin done
A Karmic Koala o
$ sudo update-grub Found Debian background: Windbuchencom.tga Updating /boot/grub/grub.cfg ... Found linux image: /boot/vmlinuz-2.6.28-11-generic Found initrd image: /boot/initrd.img-2.6.28-11-generic Found memtest86+ image: /boot/memtest86+.bin done
En versions anteriors d'Ubuntu per tal d'escriure els canvis a la configuració de GRUB.
Recursos:
This expanded procedure accounts for most of the complications that could occur, including problems connecting to the Internet in the chroot, not knowing which kernel package to install (before Ubuntu 12.10, it will not always be linux-image-generic), not knowing at the outset which partition or even which physical drive contains the / filesystem, and having a separate /boot partition.
I have not written this with reference to any of the other procedures here, though you will notice some similarities. I did base it, loosely, on the procedure here (though those instructions are for something quite different, I have adapted them extensively, and only some commands, not prose, are copied).
You removed all the kernel packages, and Ubuntu cannot boot without a kernel installed. So the solution is to boot from a live CD/DVD/USB, chroot into the installed system, and install a kernel in it.
Boot from an Ubuntu live CD/DVD or live USB flash drive.
Select Try Ubuntu (not Install Ubuntu).
When the desktop comes up, make sure you are connected to the Internet. If you are not, connect to the Internet. One way to see if you are connected to the Internet is to open a web browser. You can even follow the rest of the instructions by bringing this Ask Ubuntu answer up in your web browser, in the live CD/DVD/USB system. I strongly recommend doing that.
Open a Terminal window with Ctrl+Alt+T.
In the Terminal window, run this command to list your partitions:
sudo parted -l
You'll see something like this (but it won't be exactly like this):
Model: VMware, VMware Virtual S (scsi) Disk /dev/sda: 21.5GB Sector size (logical/physical): 512B/512B Partition Table: msdos
Number Start End Size Type File system Flags
1 1049kB 20.4GB 20.4GB primary ext4 boot
2 20.4GB 21.5GB 1072MB extended
5 20.4GB 21.5GB 1072MB logical linux-swap(v1)
Warning: Unable to open /dev/sr0 read-write (Read-only file system). /dev/sr0 has been opened read-only. Error: Can't have a partition outside the disk!
Examine the output you got, to determine the device name of the partition that contains the / filesystem of the Ubuntu system that is installed on the hard drive (that you are repairing).
If you only have one ext4 partition, that's the one.
If you have more than one ext4 partition, it's probably the first one. However, if the first one is very small--less than a gigabyte--then that might be a separate /boot partition (remember that one too).
Please note that whether or not boot is listed under Flags has very little to do with whether or not a partition is a separate /boot partition. My system, whose information is listed above, does not have a separate /boot partition.
The device name for the partition starts with the device name for the physical drive, stated immediately after Disk in the second line. Then just add the partition number to the end of that. So, the device name for the partition that contains my / filesystem is /dev/sda1. Here are the two lines where I found that information:
Disk /dev/sda: 21.5GB
1 1049kB 20.4GB 20.4GB primary ext4 boot
If you have more than one physical drive, you'll get more than one listing like what is shown above. But unless you have another Unix-like system installed, you probably will only have one drive that contains ext4 partitions, at least without having created them intentionally on another drive. If you do have multiple drives with ext4 partitions, then the ext4 partition that contains your / filesystem is probably on a drive that also contains a linux-swap partition.
It's possible that your Ubuntu system's / filesystem is on a partition of type other than ext4. When this happens, it's almost always ext3, and almost always on a quite old system. It's very uncommon for this to be the case, unless you intentionally set things up this way yourself.
Remember the device name of the partition that contained your / filesystem (or write it down). If it's different from /dev/sda1, then you'll replace /dev/sda1 with it in the steps below.
(If it looked like you have a separate /boot partition, remember the device name for that, too.)
Mount the / filesystem to /mnt, and mount its /dev filesystem:
sudo mount /dev/sda1 /mnt sudo mount --bind /dev /mnt/dev
Check if the broken Ubuntu system you're repairing has a separate /boot partition which must be mounted separately. (If you are sure it does not, you can skip this.)
To check, run:
ls /mnt/boot
If there is output (like grub memtest86+.bin memtest86+_multiboot.bin, but not necessarily exactly that), then the broken system's /boot is on the same partition as its / and you don't have to mount anything to access it.
But if there is no output, then you will have to mount the /boot filesystem:
sudo mount BOOT-PARTITION /mnt/boot
Replace BOOT-PARTITION with the device name of the /boot partition (see step 6 above).
chroot into the broken system, mount the remaining important virtual filesystems, and set some important environment variables:
sudo chroot /mnt mount -t proc none /proc mount -t sysfs none /sys mount -t devpts none /dev/pts export HOME=/root export LC_ALL=C
Determine if Internet access works from within the chroot by pinging some reliable host that is known to respond normally to pings:
ping -c 5 www.google.com
You should see something like this:
PING www.l.google.com (74.125.131.147) 56(84) bytes of data. 64 bytes from vc-in-f147.1e100.net (74.125.131.147): icmp_req=1 ttl=44 time=61.3 ms 64 bytes from vc-in-f147.1e100.net (74.125.131.147): icmp_req=2 ttl=44 time=62.3 ms 64 bytes from vc-in-f147.1e100.net (74.125.131.147): icmp_req=3 ttl=44 time=61.8 ms 64 bytes from vc-in-f147.1e100.net (74.125.131.147): icmp_req=4 ttl=44 time=63.8 ms 64 bytes from vc-in-f147.1e100.net (74.125.131.147): icmp_req=5 ttl=44 time=66.6 ms
--- www.l.google.com ping statistics --- 5 packets transmitted, 5 received, 0% packet loss, time 4006ms rtt min/avg/max/mdev = 61.367/63.212/66.608/1.897 ms
If it looks mostly like that, and the number before % packet loss is less than 100, then the Internet connection in the chroot is working:
5 packets transmitted, 5 received, 0% packet loss, time 4006ms
It's working, so you can skip step 11.
If it looks mostly like that, and the number before % packet loss is 100, the connection needs troubleshooting. Make sure the connection on the live CD system (for example, through a web browser, or by running the same command in a separate, non-chrooted Terminal tab/window) works. Make sure you're typing the command correctly. Use www.google.com if you haven't been.
If the output doesn't look like the above at all, but instead says ping: unknown host www.google.com, then networking isn't working yet in the chroot.
Set up networking in the chroot. Skip this step unless you got an unknown host error in step 10 above.
To set up networking, back up the broken system's hosts file, and copy over the live CD system's hosts and resolv.conf files. (You don't have to back up the broken system's version of resolv.conf, as that file is automatically regenerated on-the-fly.)
Open a new Terminal tab (Ctrl+Shift+T) or, if you prefer, a new Terminal window (Ctrl+Shift+N, or just Ctrl+Alt+T). Run these commands in it:
sudo cp /mnt/etc/hosts /mnt/etc/hosts.old sudo cp /etc/hosts /mnt/etc/hosts sudo cp /etc/resolv.conf /mnt/etc/resolv.conf exit
(The exit command at the end closes the new tab/window.)
Repeat step 10 above to make sure Internet access works now from within the chroot. It should.
Figure out which kernel package should be installed. Usually, this will be linux-image-generic. But not always.
If you're not sure which to install, it will depend partly on which Ubuntu release you have installed, and partly on other information. If you are not sure which Ubuntu release you have installed, find out by running this command (in the chroot, not in a separate Terminal window/tab):
lsb_release -r
On Ubuntu 12.10 (the next Ubuntu release, currently in development), it always will be linux-image-generic. (See this, this, and this.)
On Ubuntu 12.04 LTS, likely possibilities are linux-image-generic and linux-image-generic-pae. (Unlike previous versions, 12.04 no longer has separate server and desktop kernels.)
If the installed Ubuntu system (that you are fixing) is the 64-bit version, use linux-image-generic. (linux-image-generic-pae only applies to 32-bit systems.)
It's possible to have a 32-bit Ubuntu system installed on a 32-bit or 64-bit computer. Furthermore, you might be using a 32-bit or 64-bit live CD to fix a 32-bit installed system. So if you don't know whether the installed Ubuntu system is 32-bit or 64-bit, check by running this command (in the chroot, not in a separate Terminal window/tab):
dpkg-architecture -qDEB_HOST_ARCH_BITS
The output will be either 32 or 64.
(Please note that uname -m is not a correct way to find this information, because even when run in the chroot, that will tell you the architecture of the running kernel, which is the live CD system's kernel and not the installed (broken) system's kernel.)
If the installed Ubuntu system (that you are fixing) is the 32-bit version, the best kernel to use will depend on how much RAM you have. I recommend:
linux-image-generic if you have less than 3 GB of RAM
linux-image-generic-pae if you have 3 GB of RAM or more.
(This is how Ubuntu's installer chooses which one to set up, ever since the installer gained the ability to install PAE kernels. See the resolution to this bug. If you want to learn what PAE is, see this Wikipedia article. If you want to learn about PAE in Ubuntu, see this Ubuntu wiki page.)
If you don't know how much RAM you have, run this command to find out:
grep MemTotal /proc/meminfo
That is listed in kilobytes. To convert to gigabytes, divide by 1,048,576 (10242).
3 gigs = 3,145,728 kB
On Ubuntu releases before 12.04, likely possibilities are linux-image-generic, linux-image-generic-pae, and linux-image-server.
If you're running an Ubuntu Server system, use linux-image-server.
Otherwise, follow the advice above for 12.04 systems.
This is the moment you've been waiting for! Install a kernel in the broken system.
(Like before, except where explicitly indicated otherwise, these commands are run in the chroot, not in a separate Terminal window/tab.)
apt-get update apt-get -y install linux-image-generic
Replace linux-image-generic with whatever other kernel package you decided to install in step 12 above, if different.
If you had to perform step 11 to set up networking in the chroot, restore the old hosts file. If you skipped step 11, skip this step too.
To restore it, run this command:
cp /etc/hosts.old /etc/hosts
Unmount filesystems, exiting out of the chroot:
umount /proc || umount -lf /proc umount /sys /dev/pts exit sudo umount /mnt/dev /mnt
Shut down the live CD/DVD/USB system, removing the live CD/DVD or USB flash drive. Boot into the system installed on the hard drive, that you just repaired. You've installed a kernel package in it (and as part of the installation, the kernel it provides will be added back to the GRUB2 boot menu). If everything worked correctly, your system should boot without problems. (I think it's possible that it will take a little longer to boot than usual, this time.)
I did test the above procedure, of course. (And I have used essentially the same procedure in the past.) But I did not test it on every possible Ubuntu system, so it is possible there is a mistake in it that I have not identified. If you experience problems, please comment.
In the future, I recommend always trying to keep two kernels installed. It's good to have two in case one of them stops working for any reason (you can select the other in the GRUB2 boot menu). Plus, if you intend to keep two kernels and you accidentally uninstall one more than you meant to and reboot, you still have one left to boot from.
Recursos:
La sol·lució temporal és posar el timeout a un valor positiu (a l'exemple 10) al fitxer /etc/grub.d/00_header:
make_timeout ()
{
cat << EOF
if [ "\${recordfail}" = 1 ]; then
set timeout=10
else
set timeout=${2}
fi
EOF
A partir de la 12.10 es pot afegir el paràmetre:
GRUB_RECORDFAIL_TIMEOUT=0
Al fitxer /etc/default/grub
I cal executar:
$ sudo update-grub
Cal modificar el fitxer:
$ sudo [joe]] /etc/default/grub
Cal comentar les línies:
GRUB_HIDDEN_TIMEOUT=0 GRUB_HIDDEN_TIMEOUT_QUIET=true
Afegint un # al inici de la línia:
#GRUB_HIDDEN_TIMEOUT=0 #GRUB_HIDDEN_TIMEOUT_QUIET=true
Assegureu-vos també que teniu un valo de GRUB_TIMEOUT diferent de 0 (nombre de segons que teniu per escollir una opció del menú).
NO oblideu de fer:
$ sudo update-grub
Per tal d'aplicar els canvis.
Presioneu qualsevol tecla per tal de continuar. Seleccioneu la opció:
Chainload into GRUB 2
Pressioneu la tecla e per tal d'editar-la. Seleccioneu la opció:
root xxxxxxxxxxxxxxxxxxxx
On xxxxxxxxxxxxxxxxxxxx és el UUID del vostre disc dur. Torneu a editar premen la tecla e. Canvieu root per uuid:
uuid xxxxxxxxxxxxxxxxxx
I ara executeu b per iniciar amb els nous canvis. Per fer aquests canvis permanents cal editar el fitxer /boot/grub/menu.lst.
Recursos: