There are two common ways I’ve seen users have trouble logging in to their computer:
- Wrong password (either mistyped or forgotten)
- Their disk is full, which prevents login-specific files from being created, which prevents the login.
In the first case, after attempting to log in the user gets a message “Invalid password, please try again”. The problem in this case is fairly clear, as well as the possible solutions: confirm that you’re typing the characters correctly; confirm that your keyboard layout is what you expect it to be; reset the password if necessary.
In this post, though, I’ll deal specifically with the 2nd case. Because if this happens there is no feedback. The screen briefly goes dark as if to continue to the desktop, but then returns to the login screen with no message or explanation.
The solution is to free up at least a couple MB of space on the disk. There are a couple of ways to do this, but the simplest is probably to login to a command line interface instead of a graphical interface (i.e. the normal way).
At the login screen type [Ctrl]+[Alt]+F2 to open a command line prompt. You should see something like this:
Ubuntu 20.04.1 LTS {computername} tty2
{computername} login:
Type your user name and press [Enter], then type your password (the password line will remain blank as you type–just keep going) and press [Enter]. Here’s what you’ll see as you type your password (my computer name here is “test-VirtualBox”; yours will be different):
Ubuntu 20.04.1 LTS test-VirtualBox tty2
test-VirtualBox login: test
Password: _
Confirm that the problem is a full disk by typing the following command then [Enter] (the part up to the "$ " will be automatically filled in; just type “df -h”):
test@test-VirtualBox:~$ df -h
Scan the list of “Filesystems” for one that in the last column says it’s “Mounted on” “/”. It’s the third Filesystem mentioned in the list above, “/dev/sda5”. If the “Use%” (5th column) is 99% or 100%, then you’ve confirmed that the problem is a full disk. You need to proceed to deleting at least a few MBs to free up enough space to log in normally.
The easiest next step is to delete a single large file (a video or audio file should be sufficient, or maybe a large file in your Downloads folder). Let’s say you know you have large videos in your “Videos” folder. You can show all the files in your Videos folder like this (remember, on Wasta all characters are case-sensitive):
test@test-VirtualBox:~$ du -ah Videos/
1.1G Videos/Big Video.mp4
1.1G Videos/
test@test-VirtualBox:~$
So we see here a video “Big Video.mp4” that’s 1.1 GB in size. So we’ll delete that one, assuming it’s either not too important or can be replaced. To delete it you will enter the following command:
test@test-VirtualBox:~$ rm “Videos/Big Video.mp4”
test@test-VirtualBox:~$
The quotes are necessary to avoid problems with the space in the filename. Confirm that it has been deleted with the same command you used to check the size of the Videos folder:
test@test-VirtualBox:~$ du -ah Videos/
4.0K Videos/
test@test-VirtualBox:~$
Confirm that you now have space again in your “/” filesystem:
test@test-VirtualBox:~$ df -h
Again, it should say something less than 99% or so for the Filesystem mounted on “/”.
Logout of the command line interface with:
test@test-VirtualBox:~$ exit
Switch back to the login window by typing [Ctrl]+[Alt]+F7.
Try once again to login normally. It should succeed. Then be sure to clear up a total of maybe 2 GB of space from your hard drive by removing other unnecessary large files. This will help avoid this problem in the future.