How can I reallocate an ext4 file system in an extended partition without lose data?

Question

I resize the disk using the Windows default program.

I don't know why, the extended partition of Linux now result unallocated. I'm sure I don't "touch" the extended partition, and I don't know why that partition now is unallocated.

The extended partition is divided in two: one I used for my /home folder, the other for the swap.

My first preoccupation is to don't loose the data in my /home and I suddently try to take a backup of the folder. Unfortunately linux could see just the / ('cause I installed the root and the user folder separately), but when I try to copy the /home ( I try rsync ) it's impossible to accede on the data (the /home seems to be empty). 'cause the folder seems to be unallocated. I read:

Warning: extended partition does not start at a cylinder boundary.
DOS and Linux will interpret the contents differently.

the situation on my disk is this:

/dev/sda1    ntfs    windows(boot)
/dev/sda2    ntfs    Data
/dev/sda3    ext4    /
/dev/sda4    extended
        unallocated !!!  (this was the /sda6, my /home)
        /dev/sda5    swap

So I think that the data was on the disk, but now is unallocated. Is there a way to reallocate it without format all the data? or there are program to recovery data deeply, even if the file system is not allocated?

Answer 1

First, please boot a Linux emergency system and provide the output of the following commands:

sudo fdisk -l
sudo parted -l

Edit your original post or provide a link to a pastebin site with the relevant output. (If you post the information directly, please precede each line with four spaces. That will make the output easier to read and interpret.)

Second, ignore the "extended partition does not start at a cylinder boundary" message; it's irrelevant. (If you're historically inclined, it refers to the obsolete practice of starting partitions on cylinder boundaries. This practice has been pointless for at least fifteen years, and is detrimental today, so it's no longer done by modern software. Any software that still complains about partitions that are not so aligned is outdated.)

Third, if you want to press ahead without further input, the TestDisk utility may be able to recover your data. Before running it, though, I recommend carefully doing a full-disk backup of your current disk to another disk. You can do this with dd, as in sudo dd if=/dev/sda of=/path/to/backup-file.img. You may need to buy a new disk to hold this backup; and it's conceivable that your current disk's identifier will change from /dev/sda to /dev/sdb when you attach the new disk, so be careful with that. You'll have to partition the new disk, prepare a partition on it, and mount that partition somewhere (/path/to in my example command).