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Bootloader / multi-boot

Bootloader / multi-boot. Bootloaders. Grand Unified Bootloader (GRUB) Linux Load (LILO). GRUB. Discovers boot images, kernels, and root filesystems from GRUB command shell Stores boot info in a filesystems (not the MBR) Reads filesystems and kernel executables

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Bootloader / multi-boot

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  1. Bootloader / multi-boot

  2. Bootloaders • Grand Unified Bootloader (GRUB) • Linux Load (LILO)

  3. GRUB • Discovers boot images, kernels, and root filesystems from GRUB command shell • Stores boot info in a filesystems (not the MBR) • Reads filesystems and kernel executables • Does not restrict user to disk geometry • OS independent • Store GRUB in a separate boot partition • Remove and reinstall OS’s w/o having to reinstall the bootloader

  4. GRUB and LILO • Can boot non-Linux systems • Windows, OS/2, BSD, etc • Chain loading • Points to OS’s bootloader (ie, Windows)

  5. MBR • First 512 bytes of the first sector of the first partition on a drive • Contains partition table and 1st stage bootloader • 1st stage is first 445 bytes • Point to 2nd stage loader • Stored in /boot directory • Remaining 66 bytes • Partition table

  6. Linux • Limited to 63 total partitions per IDE drive • 3 primary • 4th: contains up to 60 logical partitions in a single extended partition • SCSI drives • Limited to 15 partitions • 3 primaries • 12 logicals

  7. Scenario • LILO installed, you wish to install GRUB • Determine the version of grub $grub –version grub (GNU GRUB 0.94) • Hard copy your partition table fdisk –l | lpr • Hard copy lilo.conf • Back up data • Keep rescue disk handy • LILO boot or Knoppix • Leave LILO intact… in case • Create GRUB boot diskette • Install GRUB to MBR • Boot the system • Edit GRUB configuration file • menu.lst

  8. Scenario • Create GRUB boot diskette /grub/i386-pc (can vary) could be in /usr/lib or /usr/share or… • Copy stage1 and stage2 to diskette with dd command $ dd if=stage1 of=/dev/fd0 bs=512 count=1 • Reboot the system (you get the GRUB screen) • Find the root device grub> find /boot/grub/stage1 (hd0,0) • Set the root device grub> root (hd0,0) • Install GRUB to MBR grub> setup (hd0) • Set the root device (again) grub> root (hd0,0) • Enter the path to the kernel and the root filesystem (in lilo.conf) • MAKE SURE YOU APPEND “ro” (read only) grub> kernel /boot/vmlinuz-2.4.21 root=/dev/hda1 ro • Now, boot the system grub> boot

  9. Gotchas • Linux refers to drives as hd1, hd2, etc… • GRUB starts with “0” (h0, h1, etc) • Both SCSI and IDEs are hd, floppies are fd • Linux primary partitions • 1-4 • 5 and up.. Extended partitions • GRUB • 0-3 primary • 4 and up extended • Identifying the root filesystem does not use GRUB’s numbering sytem grub> kernel /boot/vmlinuz-2.4.21 root=/dev/hda1 ro

  10. Install GRUB w/o floppy • Start a grub shell # grub • Find the stage1 loader grub> find /boot/grub/stage1 (hd0,0) • Run grub> root (hd0,0) grub> setup (hd0) grub> quit • Reboot

  11. Multi-booting Linux • Standalone /boot partition • Shared /home and /swap partitions • Standard Fedora install (on 20Gb IDE) • /dev/hda1 primary 100Mb /boot • /dev/hda2 primary 2,500Mb / • /dev/hda3 primary 3,000 Mb /home • /dev/hda4 extended • /dev/hda5 256Mb /swap • Free space 14,144

  12. Disk Druid • Used to partition • Delete any existing partitions • Highlight ‘free space’ • Click ‘new’ • Mountpoint is /boot ext2, 100Mb • Select ‘free space’ again • ‘new’ • Mountpoint is “/” ext3, 2500Mb • Next • /home ext3, 3000Mb • Find “swap” no mountpoint, 256Mb • When done, save changes using Disk Druid • Continue install, using GRUB (not LILO)

  13. QTPared • Create, delete, move and resize partitions • Included on Knoppix • Can be used to set up partitions even before new Linux install • Can be used to make changes to partitions even if data on them • /swap • Performance issues, put in its own partition • Shared on multiboot system • /home • Own partition • Share between different Linux systems • Not forced to restore data from backup when installing or removing systems

  14. Adding another Linux • Add additional Linux systems into logical partitions • Create a GRUB boot menu entry for each • After 1st Linux installed • Boot install of the new Linux • Partition and drive layouts • Highlight “free” and select “new” • 2500Mb for size (mountpoint is “/”) • Select filesystem type and initialize it (/dev/hda6) • Select /dev/hda3 to “Modify” • Select /home and ext3, do not initialize it • When done, write the partition info to disk • When prompted, you should only be formatting or initialing the “/” partition • Do NOT overwrite the MBR • Do you want Linux to handle booting system? “NO” • You want boot files installed to first sector of the root partition (/dev/hda6) • Use GRUB grub> root (hd0,0) grub> kernel / boot/vmlinuz-2,4,21 root=/dev/hda6 ro grub> boot

  15. Finding the boot parameters using GRUB • As grub is booting up, hit “c” • Get to the GRUB command shell grub>root (hd0, <tab> [tab completion] • possible partitions identifies along with filesystem type and partition type • Try them if needed… grub> root (hd0,0) • Search for kernel image grub> kernel /boot/vmlinuz<tab> • May report file not found grub> root (hd0,1) grub> kernel /boot/vmlinuz<tab> possible files are: vmlinuz vmlinuz-2.4.2 grub> kernel / boot/vmlinuz-2,4,21 root=/dev/hda2 ro grub> boot

  16. Miscellaneous • grub> cat /etc/shadow • grub> root(hd<tab> • Possible disks are: hd0 hd1 • Grub can be password protected • Documentation

  17. GRUB boot menu • /boot/grub/menu.lst • “stanza” • GRUB boot entry title Fedora 1 core root (hd0,0) kernel /boot/vmlinuz-2.4.22-1 root=/dev/hda1 ro initrd /boot/initrd-2.4.22-1.img • Title: required, can be anything • Each OS requires a stanza entry • Initrd: ramdisk (not all Linux implementations require a ramdisk)

  18. GRUB boot menu • menu.lst (or grub.conf) • Default entry • Number of the stanza (sequential) • Timeout entry • How long to wait for default entry to boot • splashimage • defaultsaved • Last image used to boot is saved as the next default

  19. Adding Windows to a Linux system • Different considerations for 95 thru ME as opposed to NT/2000/XP • XP • Make sure there’s enough free space and unused primary partition • Hard copy the partition table • Note what’s installed on each partition • Install from CD • Install complete • Restore the GRUB to the MBR • Load GRUB boot floppy grub> root (hd0,0) grub> setup (hd0) grub> reboot • Boot to Linux, and make an entry for the Windows system title WindowsXP on /dev/hda4 rootnoverify (hd0,3) makeactive chainloader +1

  20. Restore GRUB to MBR w/Knoppix • If installation of Windows overwrote the MBR and GRUB with the Windows Boot Menu you can no longer boot to Linux • Boot the Knoppix CD • su to root and run GRUB • Put GRUB onto the MBR grub> Root (hd0,0) grub> setup (hd0) grub> quit • Reboot and GRUB menu appears

  21. Password protecting GRUB # grub-md5-crypt • Copy and paste the encrypted password into menu.lst before the boot stanzas password –md5 $1$riAfJ0$QTuA1S/BGqlkYHQADZejs1 Or… plaintext password can be used… password mypasswordisthis • Chmod the menu.lst file if needed (root only) • When booting GRUB, hit “p” and enter the password to unlock the command shell • Users can still select.. Just can use command shell • (**** if you forget the GRUB password, anyone can simply boot with rescue disk and edit menu.lst *****)

  22. Assignment: • Install Red Hat on box w/GRUB • Install Mandriva as second Linux • Install Windows XP as third system

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