'Morning hydrurga,
If you're willing to continue your assistance, I'll carry on, I may even learn something (I'll need to write it down though).

The update policy is the minimum.

Information reads:
03.14@07:21 ++ Launching mintUpdate
03.14@07:21 ++ Starting refresh
03.14@07:21 ++ Initial refresh will happen in 10 minutes, 0 hours and 0 days
03.14@07:21 ++ Found 1 software updates
03.14@07:21 ++ Refresh finished

Preferences:
Options: 1st, 5th, 7th
Levels: 1 and 2
The blacklist is rather long, I presume that this is a list of those updates which I have chosen to ignore (and of course I don't remember why). The answer to my problem may well lie in there. I'll get it to you later but I will be out until early afternoon today.

I'm still here hydrurga, every time I start out something else crops up. All my contemporaries retired to lives of luxury and leisure years ago, how did I get it so wrong?
The blacklist wouldn't allow me to copy it so I took a couple of screenshots. They are attached here.
Many thanks, starkadder

Hi Starkadder.

I am surprised that you have any blacklisted programs at all. You're right, that could well be the problem.

Here are my settings:

. Let me review sensitive updates.

. 1,5,6,7

. Levels 1-4 visible, levels 1-2 selected

. Blacklisted: none

Note though that I have to date always selected all suggested updates after a quick review, which is equivalent to the apt update then apt upgrade that you did before.

Thanks hydrurga,
If you agree that the following is a sensible course of action, this is what I plan to do:
I'll remove all the blacklisted stuff and set my update manager the same as yours. This problem only appeared after I used the update manager to upgrade the distro so I'll do what I have always done in the past and run-

sudo apt-get update && sudo apt-get dist-upgrade

If that doesn't work it may be that a new, clean install is the best way forward.

As ever, I appreciate your input.

Did you set up TimeShift as I suggested earlier? It would be a good idea for you to have at least one system snapshot so that you can roll back if things go awry.

The command line (apt) knows nothing of how Update Manager is configured. Update Manager acts as a layer above Synaptic which acts as a layer above apt. So, you need to change the settings in the Update Manager and then test Update Manager itself (wait a few days until some updates come in if necessary). Don't run a dist-upgrade yet until your system is completely up-to-date without it and we're happy that Update Manager is working correctly.

Sad to report, no change.
I re-set my update manager so that it matched yours and refreshed it, (twice).
The only update offered was the kernel and I was unable to install that, it looks as if I've really broken update manager but I don't know how.


I've yet to install TimeShift but I will although my home directory is frequently backed up to an external drive together with the usr directory.

Thank you for your continued support and your time.

Dash.

You could try reinstalling the Update Manager (quit it first by right-clicking on the panel icon):

Hello hydrurga,
I've re-installed mint update but I get the same result as before (kernel update offered but unable to install)

Just installed timeshift, apparently successful, results below if it helps.

sudo timeshift --create
First run mode (config file not found)
Selected default snapshot type: RSYNC

(process:4089): Gtk-CRITICAL **: gtk_icon_theme_get_for_screen: assertion 'GDK_IS_SCREEN (screen)' failed

(process:4089): Gtk-CRITICAL **: gtk_icon_theme_append_search_path: assertion 'GTK_IS_ICON_THEME (icon_theme)' failed
Selected default snapshot device: /dev/sda1
------------------------------------------------------------------------------
Estimating system size...
Creating new snapshot...(RSYNC)
Saving to device: /dev/sda1, mounted at path: /
Synching files with rsync...
Created control file: /timeshift/snapshots/2018-03-15_07-11-06/info.json
Parsing log file...
RSYNC Snapshot saved successfully (1422s)
Tagged snapshot '2018-03-15_07-11-06': ondemand

It's of scant consolation, but you're not alone:

https://forums.linuxmint.com/viewtopic.php?t=244016

I can't see anything in that thread that will help though.

A fresh install is looking more attractive by the minute, but you could try reinstalling Synaptic (which someone else implicated here: https://forums.linuxmint.com/viewtopic.php?t=241753):

Curiouser and curiouser - I re-installed synaptic.
Launching it from the menu I get a notice advising me that it is launched without administrator privileges and if I select something to install the "apply" button remains greyed out i.e. synaptic doesn't work.
So, I launched it from the command line "sudo synaptic", it launched and worked.
I then launched the update manager "sudo mintupdate" in addition to the kernel I got dpkg and guess what? I could install it!
The problem appears to be that privileges are not being assumed as they used to be when launching from the menu and I can't help wondering is the recurring warning "gtk-CRITICAL" when using the terminal is part, or all of the problem.
Any ideas?

I couldn't see anything in the thread you mentioned either and the only reasons I haven't given up and done a fresh install is the fact that you've been so helpful and generous with your time, that and my bloody minded curiosity.
Starkadder.

Can you right-click on the Synaptic menu shortcut and determine exactly which command that shortcut represents. Then issue that command in the terminal and see what output you get?

In my opinion, you can ignore the gtk-CRITICAL error. I get that too sometimes and my system is working fine at the moment.

Just a quick note that if you are launching a GUI program as root from the command line then it is better to use gksudo rather than sudo i.e. gksudo mintupdate. For anyone else reading who is using KDE, you would use kdesudo.

With your bloody-minded curiosity and my Scottish terrier-like mentality, we might get there.

The command is "synaptic" I changed this from "synaptic-pkexec" (see original post) because it didn't work.
Changing the command back to "synaptic-pkexec" doesn't work - nothing happens.
Typing "gksudo synaptic-pkexec" in the terminal results in the customary request for a password (on the desktop, not in the terminal) and a perfect, operating launch.
It appears that one of my problems is that the incorrect command is being issued from the menu shortcut. Changing the command in Edit Launcher to "gksudo synaptic-pkexec" cures the problem.

EDIT Changing the shortcut command for the update manager from "mintupdate" to "gksudo mintupdate" cures that problem also!

Now all I have to do is tackle the problem of the login, it seems to me that I am not being logged in as an administrator.

Well, I reset my login preferences, without much hope, and low and behold, I'm back to normal - how does that work?
I've only tried one re-boot so far and as the login problem had a random element in it I'll wait a while before I mark the post solved.
Hydrurga, thank you. Without your knowledge and support I would never have got this far, hopefully I've learned something by taking this route rather than the easy option of a reinstall.
Starkadder.

Well that looks good.

It's unusual that the menu shortcuts need a gksudo (both mintinstall and synaptic-pkexec should ask for a password without need for it) but as long as it's working, that's fine. Just be aware that other items on your menu that need sudo privileges may also need to be modified in the same way, but you can modify these as the need arises.

I think that the login preferences may have been affected by a change in login managers but, again, if it's working then all is good.

If everything works out over the next few days then your system appears good to go but, given that you have encountered unusual issues, it might be worthwhile to do a fresh install of Mint 19 when it comes out, probably in June.