Palo Alto Networks firewall stores downloaded software versions for convenience to revert back to an older version if needed.
As you upgrade your firewall to new versions, you might want to clear disk space by removing older and unnecessary files.
You have the ability to do this inside of the WebGUI > Device > Software section. Inside there it will show what you currently have downloaded. And you will have the ability to delete versions of the software that you are not currently using. Foy example, if I am running PAN-OS 7.1.2 (Which also uses the base image 7.1.0), then if you have older versions os PAN-OS, like 7.0.1 or 6.1.0, then you can delete them without impacting the current version of PAN-OS.
Device > Software tab showing the installed versions. Use the X to delete a version that is not currently activated.
You can delete each version inside of the WebGUI by using the "X" on the right hand side to delete a version of PAN-OS that is not currently needed. Again, the current version and base version (Example PAN-OS 7.1.3 is the current version, will also use base image PAN-OS 7.1.0, and niether can be deleted). All other versions can be deleted if you need the space.
To delete these older software versions you can run the following command from CLI:
> delete software version <filename>
The command to delete PAN-OS 5.0.8 would be:
> delete software version 5.0.8
Use a ? or a <tab> to see what options are available in the CLI
Select the version you would like to delete and keep the current base version.
In this example the current version is PAN-OS 6.0.6 and I'm leaving base PAN-OS 6.0.0
Note: The location of these files reside in partition /opt/panrepo. You can run > show system disk-space before and after removing the files.
Once the old versions are removed you should see this partion decrease in size.