View source for Migrazione ad ext4 in Debian Squeeze

* Cambiare fstab per montare tutto in ext4
 sudo sed -i 's/ext3/ext4/' /etc/fstab

* Controllare
 sudoedit /etc/fstab

* Updatare l'initrd
 sudo update-initramfs -u -k all

* Reboot
 sudo reboot

* Verificare che la root sia montata in ext4. Il Filesystem è ancora compatibile ext3, in caso di problemi.
 mount | grep ext4

* Abilitare il login root con key da ssh

 sudoedit /etc/ssh/sshd_config

 PermitRootLogin without-password

 sudo invoke-rc.d ssh restart

* Copiare la key per root
 cat ~/.ssh/authorized_keys | sudo tee -a /root/.ssh/authorized_keys > /dev/null

* Collegarsi come root, ed uscire eventualmente da screen
 ssh root@hostname

* Abilitare ssh al runlevel
 sed -i -e "/^~~/ish:S:respawn:/usr/sbin/sshd -Do 'AllowUsers=root'" /etc/inittab

* Andare in single user mode:
 telinit q
 init 1

* Attendere la chiusra di tutti i serviei e la disconnessione e poi riconnettersi:

 ssh root@hostname

*Uscire da screen, chiudere tutti i processi inutili

* Montare la root readonly:
 mount -o remount,ro /

* Verificare che il filesystem sia davvero readonly
 mkdir /tmp/test

 mkdir: cannot create directory `test': Read-only file system

* Fare check:

 fsck.ext3 -pf -C0 /dev/md0

* Abilitare estensioni ext4
 tune2fs -O extents,uninit_bg,dir_index /dev/md0

* Il filesystem ora NON è più montabile come ext3

* Fare check:
 fsck.ext4 -yfD -C0 /dev/md0

* Reboot
 reboot

* Rimuovere la riga

 sudoedit /etc/inittab

 sh:S:respawn:/usr/sbin/sshd -Do 'AllowUsers=root'

* Cancellare la key root
 sudoedit /root/.ssh/authorized_keys


==Ottimizzazione==
*Se possibile, applicare questi parametri, che ottimizzano il filesystem che proviene da vecchie installazioni:
 sudo tune2fs -I 256 \
              -O sparse_super,filetype,resize_inode,dir_index,ext_attr,has_journal,\
              extents,huge_file,flex_bg,uninit_bg,dir_nlink,extra_isize \
              /dev/MYDEV

==Abilitazione extents==

Per ogni directory:

<pre>
export DIRS="
bin
boot
cdrom
etc
files
home
lib
media
mnt
opt
root
sbin
selinux
tmp
usr
var"

cd /; for DIR in $DIRS; do echo CHANGING $DIR; sudo find $DIR -xdev -type f -print0 | xargs -0 sudo chattr +e; sudo find $DIR -xdev -type d -print0 | xargs -0 sudo chattr +e; done
</pre>

* sudo reboot

'''Just a quick note of caution for other antedeluvians. I migrated to ext4 and migrated most of my filesystems back again when I found that dump/restore didn't (yet) support ext4. '''

==Riferimenti==
*[http://www.debian-administration.org/article/Migrating_a_live_system_from_ext3_to_ext4_filesystem Migrating a live system from ext3 to ext4 filesystem]
*[https://ext4.wiki.kernel.org/index.php/Ext4_Howto#Converting_an_ext3_filesystem_to_ext4 Ext4 Howto - Ext4]
*[http://debiansystem.info/readers/errata/299-sshd-single Faulty way of spawning sshd in single-user mode (page 299) — debiansystem.info]
*[http://ocaoimh.ie/how-to-umount-when-the-device-is-busy/ How to umount when the device is busy]
*[http://www.kev009.com/wp/2008/12/how-to-upgrade-to-ext4-in-place/ How to upgrade to ext4 in place | Kev009.com]