After doing a clean install of Ubuntu 18.04 in May 2018 and installing HPLIP software to be able to print on my Hewlet Packard LaserJet Pro MFP M125nw printer, printing worked correctly. Then it got broken by causes unknown to me in June and I had to fix it. This, however, didn’t go without complications.

These are steps that led to success ultimately:

1. I have installed a most recent version of HPLIP driver software from HP Developer Portal which was version 3.18.6 (hplip-3.18.6.run).

   After perfoming an automatic installation – uninstalling previous version of HPLIP, replugging the printer and letting it check for updated version – printing worked correctly.

   Scanning, however, did not work at all – XSane Image scanning program yielded an error that it does not have a HP plugin and asked whether it should try installing it.

2. Letting it download the correct version of the plugin ended with an error that the download failed:

   error: Plugin download failed with error code = 8 error: file does not match its checksum. File may have been corrupted or altered

   It instructed me to use command hp-plugin from command line to install it.

3. Running this plugin ended with the pretty much the same outcome – a failure.

4. Thus, Google search for topics about this plugin followed, pointing me to some forum threads about this. One of them pointed to this directory listing with the relevant software. Problem is that at least at that time, the latest version of the plugin was 3.18.5 (hplip-3.18.5-plugin.run) which is incompatible with the version 3.18.6 of the HPLIP.

5. With some further Google search I got to this official HP page which actually does have the correct latest version of the plugin (hplip-3.18.6-plugin.run).

6. I then downloaded two files, hplip-3.18.6-plugin.run and hplip-3.18.6-plugin.run.asc (that’s a signature of the file or something) – save those into a same directory.

7. Then I started XSane which again told me it doesn’t have the plugin, I did not let it search for the plugin on the Internet but choose to use a locally saved file (second option) and gave it the file hplip-3.18.6-plugin.run. After this, the plugin installed successfully. and scanning works.

I hope I’m not missing some important step out of this and, mainly for future’s sake, this will remain relevant for a long time if the problem persists.

Oh, looking to the backlog of the terminal – I did have forget something, I just don’t know how I got into that situation. The error of hp-plugin was this:

Segmentation fault
error: Failed to install Plug-in.
Either you have chosen to skip the Plug-in installation  or entered incorrect Password.

I have no idea what I did at that time but it certainly didn’t lead to the correct problem resolution.