Here is How to Upgrade to Linux Mint 19

As you may already know, recently Linux Mint 19 left the beta stage and became available for everyone. It is now possible to upgrade all Linux Mint releases to version 19.

It is now possible to upgrade the Cinnamon and MATE editions of Linux Mint 18.3 to version 19. The upgrade tool only upgrades Linux Mint 18.3 Cinnamon, MATE or Xfce edition.If you are running Linux Mint 18, 18.1 or 18.2, you first need to upgrade to Linux Mint 18.3 using the Update Manager.

Before proceeding, please keep in mind the following.

• Linux Mint 17.x (17, 17.1, 17.2 and 17.3) will be supported until 2019.
• Linux Mint 18.x (18, 18.1, 18.2 and 18.3) will be supported until 2021.

You should have a reason for upgrade. If everything works, then do not upgrade. You might want to upgrade to Linux Mint 19 because some bug is fixed or because you want to get some of the new features. You can always try a Live CD/USB mode to check out all the changes yourself and decide if you really need them. Linux Mint 19 offers updated software versions of essential apps, new versions of its  "x-apps", a set of apps available in all supported desktop environments, Flatpack support, TimeShift and system snaphots, and more. You can read in detail here:

Linux Mint 19 released

How to upgrade to Linux Mint 19

Here are the official instructions provided by Linux Mint community.

C. Requirements

To upgrade to Linux Mint 19 you need to satisfy the following requirements.

C1. Experience with APT and the command line

Upgrading to a newer package base is not trivial and it should not be performed by novice users.

You need to know how to type commands and read their output.

You also need to be experienced with APT.  During the upgrade you'll need to understand the output of APT commands. You'll need to understand if a package needs to be removed, if it blocks the upgrade, if it conflicts with another package etc etc.

C2. Linux Mint 18.3 Cinnamon, MATE or Xfce edition

The upgrade tool only upgrades Linux Mint 18.3 Cinnamon, MATE or Xfce edition.

If you are running Linux Mint 18, 18.1 or 18.2, you first need to upgrade to Linux Mint 18.3 using the Update Manager.

C2. Timeshift snapshot

To install timeshift, open a terminal and type:

apt install timeshift

Then launch "Menu -> Administration -> Timeshift".

Follow the wizard to select a destination for your snapshots.

In the toolbar, click on the "Create" button to make a manual snapshot of your operating system.

If anything goes wrong, you'll be able to restore your operating to this current state, either from within Linux Mint, or by launching Timeshift from a live Mint session (live DVD or live USB).

C2. LightDM

To know which display manager you are currently using, open a terminal and type:

cat /etc/X11/default-display-manager

If the result is "/usr/sbin/lightdm", you can skip this step.

If the result is "/usr/sbin/mdm", you need to switch display managers by installing lightdm and removing mdm. Open a terminal and type:

apt install lightdm lightdm-settings slick-greeter

When asked to choose a display manager between MDM and LightDM, choose LightDM.

Open a terminal and type:

apt remove --purge mdm mint-mdm-themes*

sudo dpkg-reconfigure lightdm

sudo reboot

D. How to upgrade

D1. Update your Linux Mint 18.3 system

Using the Update Manager, click on "Refresh" to refresh the APT cache and apply all updates.

D2. Give your terminal unlimited scrolling

Open a terminal.

Click on "Edit"->"Profile Preferences"->"Scrolling".

Check the "unlimited" option and click "OK".

D3. Install the upgrade tool

To install the upgrade tool, open a terminal and type:

apt install mintupgrade

D4. Check the upgrade

To simulate an upgrade, open a terminal and type:

mintupgrade check

Then follow the instructions on the screen.

This command temporarily points your system to the Linux Mint 19 repositories and calculates the impact of an upgrade.

Note that this command doesn't affect your system. After the simulation is finished, your original repositories are restored.

The output shows you if the upgrade is possible, and if it is, which packages would be upgraded, installed, removed and kept back.

It is extremely important that you pay close attention to the output of this command.

If it shows packages which are preventing the upgrade, remove them (and take note of them so you can try to reinstall them after the upgrade).

Also note any important packages in the list of packages which would be removed, so you can reinstall them after the upgrade.

Keep using "mintupgrade check" and do not proceed to the next step, until you're happy with the output.

D5. Download the package upgrades

To download the packages necessary to upgrade to Linux Mint 19, type the following command:

mintupgrade download

Note that this command doesn't actually perform the upgrade itself, but just downloads the packages.

Note also that this command points your system to the Linux Mint 19 repositories (if you want to go back to Linux Mint 18.3 after using this command, you still can, with the command "mintupgrade restore-sources").

Use the "mintupgrade download" command until all the packages are successfully downloaded.

D6. Apply the upgrades

Note: This step is non-reversible. Once you perform it, the only way to go back is by restoring a system snapshot. Make sure you've made a snapshot before following this last step.

To apply the upgrades, type the following command:

mintupgrade upgrade

E. Workarounds

E1. Boot stuck at /dev/mapper/cryptswap1

If upon reboot, the computer fails to boot and the boot sequence seems stuck, type the left or right arrow to switch from the boot logo to the boot details.

If the boot is stuck trying to run the /dev/mapper/cryptswap1 job, then do the following:

• Boot the computer with the Shift key pressed to force the Grub menu to show
• Choose "Advanced Options" for the latest kernel entry
• Choose "Recovery mode"
• Once in the recovery menu, choose "fsck" and choose "yes".
• Once fsck is done, press Enter to go back to the menu.
• Choose "root" from the recovery menu and press "Enter" to start the root console.
• Type "nano /etc/fstab" to edit the fstab file.
• Find the line with "/dev/mapper/cryptswap1" and add a # sign in front of "/dev/mapper/cryptswap1"
• Press "Ctrl+O" and then "Enter" to save the file
• Press "Ctrl+X" to exit the nano editor
• Type "reboot" to restart the computer

After a successful boot, the crypted swap might activate properly. You can try that by editing /etc/fstab again and reactivating the line for cyptswap (by removing the # sign in front of it).

Source: Mint Blog.