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--- linux:filesystems:boot [2012/04/25 12:18]
tkilla created
+++ linux:filesystems:boot [2022/11/06 21:39] (current)
tkilla
@@ Line 1: / Line 1: @@
-====== boot ======
+====== Bootloader ======
 **linux boot process tricks**
-=== howto clone harddisc and boot new system ===
+==== howto clone harddisc and boot new system ====
-**To get the system-files transfered,** it's best to get a live USB-stick or CD and boot into it \\
+**To transfer all system files,** it's best to get a live USB-stick or CD and boot into it \\
 (all live-distros from ubuntu to systemrescuecd are ok). \\
-In a livesystem, you can mount the partitions and transfer the data anyway you like:
+In a livesystem, you can mount the partitions and transfer the data anyway you like (as root user):
-. rsync:
-  parameters: " -a -v -z -h --perms -E -o -g  --times --compress --update --delete "
-  excludes: " --exclude="/proc/*" --exclude="/sys/*" --exclude="/mnt/*" --exclude="/media/*" "
-. copy with "cp":
+. **rsync** needs params and data must be excluded, (but works f&f in a running system), eg., :
-  $ sudo cp -afv /to/source/* /to/target/
-. dd - can only be used, if both partitions have exactly the same size!
+  rsync -a -v -z -h --perms -E -o -g  --times --compress --update --delete \
+        --exclude="/proc/*" --exclude="/sys/*" --exclude="/mnt/*" --exclude="/media/*" / /mnt/newsys/
-. gparted
+-> may cause strange bugs, like permissions in /var/run/, maybe /dev probs
+. simple **copy** with "**cp**" (untested):
+  cp -afv /from/sourcesystem/* /mnt/newsys/
+  [ or ]
+  cp -ax /from/sourcesystem/* /mnt/newsys/
+. **dd** - clones each sector - can only be used, if both partitions have exactly the same size!
+. **parted** - no ext4, only from livesystems
 etc...
@@ Line 24: / Line 32: @@
 ----
 \\
+**Fix partition-identifier UUIDs in fstab** of the new system.  \\
+The UUIDs need to be replaced by the new UUIDs in **/mnt/newsys/etc/fstab**
+This shows 'em all: :)
+  ls -l /dev/disk/by-uuid/
-**Fix fstab** by mounting the new disc and editing /etc/fstab in there. \\
+----
-The UUIDs need to be replaced by the UUIDs of the new disc's partitions.
+\\
-  $ ls -l /dev/disk/by-uuid/
+**Install grub2 bootloader** to the new disc - \\
+unfortunately a complete change-root environment is required to fool grub-install:
+**mount dev, proc, sys** via "bind"-option **into the new root / chroot**:
+  mount -o bind /dev /mnt/newsys/dev
+  mount -t proc none  /mnt/newsys/proc
+  mount -t sysfs none /mnt/newsys/sys
+**Enter** the new (virtual) root system:
+  chroot /mnt/newsys/
+Now inside this future system, grub2 installer scripts will work - \\
+**generate a new (/mnt/newsys) /boot/grub/grub.cfg**:
+  update-grub
+In case of error "no such disc" run
+  grub-mkdevicemap
+**Install to the MBR (no partition number) of the new disc, finally:**
+  grub-install /dev/sdX
+reboot & good luck!
-.. shows 'em all :)
 ----
 \\
-**Install grub2 - make the fresh harddisc bootable**
+** initramfs **
+the step after the bootloader needs all (fs, rais,..) modules to mount root, check: /etc/initramfs-tools/modules
+update existing initramfs:
+  update-initramfs -u -k all
+** RAID **
+if you changed your raid setup, you need to update initramfs:
+  dpkg-reconfigure mdadm
+make sure these modules are in /etc/initramfs-tools/modules
+  raid0
+  raid1
+  md
+\\
+References: http://unix.stackexchange.com/questions/5297/debian-grub2-moving-root-partition-to-new-drive
+\\
+==== howto boot from grub2 rescue console ====
+If you drop to the grub rescue after cloning a system disc or something, it's possible to boot an existing system.
+Enter this, to start a system on sda3 for example:  sda = hd0 + partition 3 = (hd0,3)
+  set prefix=(hd0,3)/boot/grub
+  insmod (hd0,3)/boot/grub/linux.mod
+if this works, the console gets upgraded to standard grub console.
+if it doesn't work, try another partition. grub counts partitions from 1 (not 0), btw.
+This boots arch linux:
+  set root=(hd0,3)
+  linux /boot/vmlinuz26 root=/dev/sda5
+  initrd /boot/kernel26.img
+  boot
+This is required to boot debian - unfortunately the filenames contain versionnumbers :(
+  set root=(hd0,3)
+  linux /boot/vmlinuz-3.1.0-1-amd64 root=/dev/sda3
+  initrd /boot/initrd.img-3.1.0-1-amd64
+  boot
+This should boot your system. Just re-install grub:
+  update-grub
+  grub-install /dev/sdX
+===== Bugs =====
+Inside a chroot, grub complains
+  # update-grub
+  Generating grub configuration file ...
+  WARNING: Device /dev/ram0 not initialized in udev database even after waiting 10000000 microseconds.
+  ...
+Fix:
+Outside chroot /debian/:
+  mkdir /debian/run/udev
+  mount --bind /run/udev /debian/run/udev
+  mount --bind /run/udev /mnt/run/udev
+===== Crypto Bugs =====
+Grub complains root device couldn't be found
+Fix:
+- set
+  GRUB_ENABLE_CRYPTODISK=y
+  apt install cryptsetup-initramfs lvm2
+- if it is a brtfs, set in /etc/initramfs/modules
+  btrfs
+Commands to execute in chroot to reinstall grub:
+  update-initramfs -c -k all
+  grub-install /dev/sdX
+  update-grub
-  $ grub-install --root-directory=/to/target-mountpoint/ /dev/sdX --recheck
+If update-grub echos: "cannot find device for / in fstab" and you have a btrfs rootsys:
+  mount -o "subvol=@" /dev/mapper/vgubuntu-root
+is required to mount the @ subvol!

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