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--- linux:filesystems:boot [2012/04/25 16:57]
tkilla
+++ linux:filesystems:boot [2022/03/12 21:14]
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 transfer all system files,** it's best to get a live USB-stick or CD and boot into it \\
@@ Line 13: / Line 13: @@
   rsync -a -v -z -h --perms -E -o -g  --times --compress --update --delete \
-        --exclude="/proc/*" --exclude="/sys/*" --exclude="/mnt/*" --exclude="/media/*"
+        --exclude="/proc/*" --exclude="/sys/*" --exclude="/mnt/*" --exclude="/media/*" / /mnt/newsys/
+-> may cause strange bugs, like permissions in /var/run/, maybe /dev probs
 . simple **copy** with "**cp**" (untested):
@@ Line 25: / Line 26: @@
-. **gparted** - no ext4, only from livesystems
+. **parted** - no ext4, only from livesystems
 etc...
@@ Line 33: / Line 34: @@
 **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/
+  ls -l /dev/disk/by-uuid/
-.. shows 'em all :)
 ----
 \\
-**Install grub2 bootloader to the new disc** -
+**Install grub2 bootloader** to the new disc - \\
-unfortunatly a complete change-root environment is required to fool grub-install:
+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 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:
+**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 and install to the MBR (leave out partition number):
+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!
+----
+\\
+** 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

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