How can I upgrade packages on a broken ubuntu installation from a live usb?

Question

I downgraded from linux-image-3.19.0-18-generic to linux-image-3.19.0-16-generic and then stupidly removed 3.19.0-18 without thinking. When I rebooted I was unable to load unity and my network connection failed to initialize even if I entered recovery mode and selected the option to start networking.

I have an ubuntu usb and I could reinstall ubuntu, but instead I'd prefer to revert my broken installation to its previous condition by reinstalling linux-image-3.19.0-18-generic (or even better, upgrading to linux-image-3.19.0-19-generic). Is it possible to do this from an ubuntu live usb?

Also, I'd appreciate any advice as to whether this is the sanest way to approach this problem.

Answer 1

• Boot from the live USB
• Find out where the existing disk is mounted - say it is mounted on /media/point
• Download http://ppa.launchpad.net/canonical-kernel-team/ppa/ubuntu/pool/main/l/linux/linux-image-3.19.0-18-generic_3.19.0-18.18_amd64.deb (for a 64 bit system) or http://ppa.launchpad.net/canonical-kernel-team/ppa/ubuntu/pool/main/l/linux/linux-image-3.19.0-18-generic_3.19.0-18.18_i386.deb (for a 32 bit system) and move the downloaded file to /media/point
• Open a terminal and execute chroot /media/point
• execute dpkg -i linux-image-3.19.0-18-generic_3.19.0-18.18_*
• Power off, unplug the live USB and boot. Then upgrade to linux-image-3.19.0-19-generic if needed.