Bug#529629: Add a note about ext3 option "data" change from "ordered" to "writeback"
Package: release-notes
This is a note that I suggest to add to the next Installation manual
since it is about a possible problem that would render your system
unusable.
Starting with 2.6.30 kernels, ext3 default mount option is now
data=writeback instead of "data=ordered". If you have "data=ordered"
in /etc/fstab then you will not be able to mount read/write your file
system after upgrading kernel from 2.6.29.
When the new kernel starts, it mount the root volume using default file
system option. Then, when remounting the file system as read/write, only
a few options can be changed. Option "data" cannot be changed.
If your /etc/fstab contain "data=ordered", the kernel will write this
message:
EXT3-fs: cannot change data mode on remount
and will not remount the file system as read/write. This will, of
course, make your system unusable (or, let's say... really secure) and
you will not be able to change /etc/fstab in any way.
The solution is to use kernel parameter "rootflags=" and specify
"data=ordered" in order to permit the switch from read only to
read/write while starting up the system. Once the system has been
mounted, change /etc/fstab removing "data=ordered" or change your boot
loader in order to always pass the appropriate rootflags.
If you are already using data=journal, since this is not a default
option, you are already also specifying rootflags parameter, so nothing
should be changed.
Bye,
Giuseppe
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