Debian Configuration :: Boots On Emergency Mode After Crash

First of all, my computer is running Debian Jessie. uname -a gives me this output: Code: Select allLinux felix-PC 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt11-1+deb8u3 (2015-08-04) x86_64 GNU/Linux

So today I updated my system with aptitude update and aptitude upgrade, and there was few paquages that were updated. Among them was one "linux-image" or "linux-headers". I believe that it is linked to this security update: [URL].... .

During the time aptitude upgrade was running, I was simply surfing on Iceweasel. However, it seems that my system suddenly restarted, without asking me the permission or without notifying me. It really looked like I pressed the restart key, but I actually didn't. My computer battery was full charged and plugged in. So, I do believe that it is my system that rebooted himself after the aptitude upgrade was completed (or even during the upgrade, I don't know).

So my computer restarts, and brings me to GRUB menu: I boot Debian and then I get the usual [ OK ] ***** lines telling that the system boots normally. But this time, I get some errors:

Code: Select all[FAILED] Failed to set up automount Arbitrary Executable file format file system Automount point
...
[FAILED] Failed to start load kernel module
...
[FAILED] Failed to mount /boot/efi
[DEPEND] Dependency failed for Local File Systems

I arrive then in Emergency mode with this message:
Code: Select all Welcome to emergency mode! After logging in, type "journalctl -xb" to view
system logs, "systemctl reboot" to reboot, "systemctl default" to try again
to boot into default mode.
Give root password for maintenance
(or type Control-D to continue):

I tried systemctl default but it doesn't boot my system normally. I also tried Control-D but it just reprints the same message. And finally I typed journalctl -xb, which gives me a long log file (855 lines) that I do not understand.

I would give this log file, but it seems that my internet connexion is broken (because of the kernel, I mean), even with an Ethernet cable. So I can't connect with ssh to the computer I use at the moment, and I can't either send it to myself by mail. I tried to mount an usb key, but it seems that any key won't be mounted because of a kernel problem.

An obvious solution to my problem may be to come back to an older kernel version. However, only the lasted kernel version (x86_64 Linux 3.16.0-4-amd64) is installed. dpkg --list | grep linux-image gives me indeed:

Code: Select alliF linux-image-3.16.0-4-amd64 3.16.7-ckt11-1+deb8u3 amd64 Linux 3.16 for 64-bit PCs
ii linux-image-amd64 3.16+63 amd64 Linux for 64-bit PCs (meta-package)

I do not know how to come back to an older kernel, as far as I haven't any internet connection and as far as I seem to not be able to load an usb key.