The TTY console in Ubuntu 18.04.3 is 800x600 by default and it is too small for the use of my virtual machines in VirtualBox where I have them open to see the logs. An example of what this 800x600 resolution looks like is:
All this configuration is in the /etc/default/ grub file and to change it you have to restart the OS and press the shift key to bring up the menu that provides access to the GRUB prompt where we can see the possible video modes:
Where we press 'c' as specified by the help on the screen to access the GRUB prompt:
We execute the 'vbeinfo' command to see the supported video modes:
The supported video modes are not displayed paged because you have not specified paging before specifying 'set pager-1', but we can already see suitable video modes such as the 0x145 of 1280x1024.
Once we have seen this, we continue with the normal boot of the system by executing the 'normal' command at the GRUB prompt.
With the OS started we edit the file /etc/defautl/ grub, requiring root permissions and specify the resolution 1280x1024. For this we execute a 'sudo vi /etc/default/grub':
We look at the comment above so after changing it run 'update-grub'.
We change the following values in the file (in my case I did not have GRUB_GFXPAYLOAD_LINUX, and I add it):
We execute (with sudo if you are not as root):
And we restart with 'shutdown -r now' to see the changes with the new resolution: