[SOLVED] MATE GDM greeter theme testing and recovery

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KirbySmith

[SOLVED] MATE GDM greeter theme testing and recovery

Post by KirbySmith »

Background:
I decided to change my welcome/login (greeter) screen by switching via 'mdmsetup' to the GDM version called 'linuxmint' (plain gray background), but swapping in the unlock background from 'usr/share/backgrounds/linuxmint-quiana/linux_mint_17.png'. With minor changes to 'themes.xml' and 'GdmGreeterTheme.desktop' this worked ok as a new GDM theme folder I named 'linuxmint17'. My next step was to be to shift the login window container and content lower to unobscure the "Linux" blocks illustrated in the background image. To do this efficiently and safely, either I need a viewer or I need a bail-out mechanism.

Viewer historical Inconvenience:
Once upon a time, there was gdmthemetester designed to test gnome themes under development. This script seems to be so obsolete that is it not only absent from the Linux and Ubuntu builds, but I can't find any sign that a repository even exists for it. It must have become unusable with gnome changes and forks.

So next came gdmflexiserver. This is still resident, but one can no longer open it in an xnest window. (Xnest is obsolescent, but available.) This capability seems to have been lost in gdmflexiserver somewhere between hardy and trusty (I didn't run it down by reviewing each distro's gdmflexiserver man page). Gdmflexiserver shows only the presently selected login greeter screen, and not one under development. Since using it leads to having to force reboot the computer each time I use it, it is not more efficient than just rebooting on a modified greeter folder.

Is there a theme viewer that doesn't require that I follow Clem's recent path of changing to HTML5, a bigger project than I want to tackle at present?

Bail-out mechanism:
Rebooting to a broken greeter theme is fraught with hazard if the problem keeps one from logging in.

If I have to make each changed theme the active theme to view it, and this breaks login, what terminal commands can I use to change the greeter theme to one known to work?

Thumbnail image:
With the loss of Gdmthemetester and Xnest mode of Gdmflexiserver, there seems to be no way short of using a digital camera to capture an image of the theme to use as a thumbnail image (necessary part of the theme folder to see what it looks like in mdmsetup). There was an approach reported based on using a timed script running after login as root, but I'd like to avoid doing that.

Is there any other way that someone can suggest?

Recovering from gdmflexiserver:
When I am in Gdmflexiserver and click the quit button that appears in greeter screen in this mode, the theme goes away leaving only a black screen with a mouse pointer. No keystrokes seem to work except cntl-alt-F1, from which I can login and shutdown. If I login to the instance, I get a new, apparently normal desktop. Logging out of this desktop gets me to the black screen.

Is there a way to get out of this state without having to do a forced reboot ? Maybe a shell command that kills only the instance and not the original login?

Thanks for any help

kirby
Last edited by LockBot on Wed Dec 28, 2022 7:16 am, edited 2 times in total.
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KirbySmith

Re: MATE GDM greeter theme testing and recovery

Post by KirbySmith »

I have begun to review information on VirtualBox, and suspect from what I've read so far that running a Mint 17 MATE guest OS inside VirtualBox running on a Mint 17 MATE host could achieve the underlying goals in my message above. I should be able to capture an image of the greeting screen in the VB using gimp or other tool on the host OS. I should be able to survive a defective login window within VB without effect on the host OS. And I should be able to shutdown any window lockup without having to reboot the host.

More on this story when I know enough to be definitive, or have results.

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Re: MATE GDM greeter theme testing and recovery

Post by Spearmint2 »

Code: Select all

mate-screenshot --interactive
Above will allow a delayed screenshot. I use it sometimes to show an open menu box on a program.
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KirbySmith

Re: MATE GDM greeter theme testing and recovery

Post by KirbySmith »

Spearmint2:
I think your command is useful to know, but I'm not sure how it can operate in the context of the greeter screen activity. Please note that when gdmflexiserver runs, it seems to create a new instance of the Xserver with a login window. I'm not sure whether the running instance can communicate with this instance. Maybe if I used two workspaces it might. (need a keyboard command to switch between right and left workspaces.) Or maybe both workspaces are taken over by the second Xserver instance. I'll have to see when I'm back at that computer.

Otherwise, in the context of my first message, how would the command be used? For example, do I type your command in a terminal, then type 'sudo gdmflexiserver' in the same or a second terminal, see the greeter screen cover my monitor screen, wait a bit for a screenshot to occur, click the quit button on the greeter screen, get a black screen, use cntl-alt-F1 to open another terminal and type 'sudo shutdown -r now' (reboot), and then after login find the screenshot somewhere? The man pages for mate-screenshot I just found on the web don't show any dialog for where the image is saved.

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Re: MATE GDM greeter theme testing and recovery

Post by Spearmint2 »

I was refering to using it for capturing the VB screen using it from the host system, but might do better on that with "Record My Desktop" used from the host system. You can set your screenshot menu launcher to that if not already. Some versions come without the --interactive switch set on it, but it can be added to the command line in your launcher. I find it very handy for delayed shots and also the cropping feature. The one used for MATE seems to be the same as gnome-screenshot program, just renamed.

I am not familiar with "gdmflexiserver".

I did try an experiment. I ran "record my desktop" in one user, logged out, logged into second user, then logged out and back into first user. No go, the logout stopped the program.

Next I decided to test on a "Switch user". The program continued to run, between switching from one user to the guest user, then back to the current user, but all it recorded is what was on the current user, not the screen itself.

Here's a trick MAC users do for getting screen captures of login; involves using a networked remote desktop connection to do it.

http://hints.macworld.com/article.php?s ... 1107163856
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KirbySmith

Re: MATE GDM greeter theme testing and recovery

Post by KirbySmith »

Aha! We are thinking along the same lines. MATE-screenshot may be the fastest way to get an image of the VB window, and then gimp can be used to clean off the boundaries. I still don't know where the image that is taken goes though, but I'm not yet back at the computer to experiment. man documentation doesn't mention the critical information of how to find the image.

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Re: MATE GDM greeter theme testing and recovery

Post by Spearmint2 »

KirbySmith wrote:Aha! We are thinking along the same lines. MATE-screenshot may be the fastest way to get an image of the VB window, and then gimp can be used to clean off the boundaries. I still don't know where the image that is taken goes though, but I'm not yet back at the computer to experiment. man documentation doesn't mention the critical information of how to find the image. k
Should default save to Pictures folder in your home folder. When you open file manager it can be seen on the side panel.
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KirbySmith

Re: MATE GDM greeter theme testing and recovery

Post by KirbySmith »

Hmmm. When I tested MATE-screensaver by starting it in a terminal on a normal desktop, it put up a window GUI with a default name.png filled in and Desktop as the destination. So I jumped to setting it up with a delay, then opened another terminal and commanded gdmflexiserver, and got a greeter screen, as usual. I waited more than the 120 seconds I had set as the delay and then had to reboot to get out of the quit lockup. There was no png file either on the Desktop, or at the top level of my home directory.

There is still the "screen" approach reported toward the end of the MAC discussion you linked to. I'll try to mess with that a bit tomorrow morning.

I haven't yet tried messing with work spaces, but I have a feeling that Xserver will initiate a new instance in both workspaces when gdmflexiserver is invoked.

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Re: MATE GDM greeter theme testing and recovery

Post by Spearmint2 »

You have more tenacity than I. I'd just pull out my digicam and record it that way.
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KirbySmith

Re: MATE GDM greeter theme testing and recovery

Post by KirbySmith »

Update:
It appears that the login greeter screen, instantiated by gdmflexiserver, either appears on all four workspaces, or doesn't allow the workspace switching keystrokes to work, because I get no change to the screen trying to change workspaces.

I tried my own brew Linux oriented version of the technique reported toward the end at your macworld forum link, but it didn't work. Some other permutations may succeed.

There are a lot of options for screen shots reported on the www, so I don't doubt that screen shots are possible (without a digital camera). I still believe, however, that the real need for using VirtualBox is to avoid becomming locked out of my computer, except for terminal access, unless terminal access is sufficient to get to the desktop.

So, this thought leads to a key question: Isn't there a command like 'run mdm' that would start the normal desktop from a logged-in terminal and bypass a possibly defective login greeter screen?

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Re: MATE GDM greeter theme testing and recovery

Post by Spearmint2 »

Isn't there a command like 'run mdm' that would start the normal desktop from a logged-in terminal and bypass a possibly defective login greeter screen?
Sure. You can test it out. I just did to be sure first. Go to a tty screen like CTRL-ALT-F1 and login, then run startx.

You can get back to the one you were at by using the F7 or F8 in key combo, whichever applies to your computer. It's supposed to be F7, but for some reason at times that won't work and then the F8 does.
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KirbySmith

Re: MATE GDM greeter theme testing and recovery

Post by KirbySmith »

Thank you, Spearmint2.

For your second suggestion, do you mean cntl-alt-F7 or F8, or just F7 or F8? And does this apply only after a new terminal login? I have tried a lot of key stroke combinations to try to get out of the black screen that I get when I close the gdmflexiserver initiated greeter screen, and the scope of those key stroke combinations should have included a pass through both F7 and F8, and CNTL-ALT-F7 and F8 (although I'm game to retest to confirm).

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Re: MATE GDM greeter theme testing and recovery

Post by Spearmint2 »

I can be in Mint MATE on the F7 screen or console, whatever it's called, or it might be on F8, but moving between consoles uses CTRL-ALT-F? to get the one you want. I can go to the F1 and login there and run startx and it will bring up the graphical display, and it's not the same instance that's over on F7 (or F8). It's similar to swapping workspaces in a way.
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Re: MATE GDM greeter theme testing and recovery

Post by KirbySmith »

OK, that was very helpful; here is preliminary news.

Having logged into a single instance of MATE some time in the past, I opened a terminal window.
I typed gdmflexiserver, as usual, and as usual got an instance of the login greeter screen
I clicked on the "quit" button on the login window and as usual got a black screen with a mouse pointer
(previously, I couldn't get out of this without cntl-alt-F1 and performing a reboot.)
I tried cntl-alt-F7 and it worked -- thank you very much, spearmint2 -- the mouse pointer dissapeared and after a brief time the desktop/console that I had been working from reappeared. I'm typing this from that console.

Although I havn't tested all of the possible paths for bailing out and getting to the console, what this implies is that I shouldn't need VirtualBox to do "safe" GDM greeter screen development. If the screen doesn't work correctly in gdmflexiserver, then I bail with cntl-alt-F7. (More complicated scenarios may await, but I think I have the information I need to survive.)

Greeter development news may be available this weekend depending on disruptions of time.

Regards

kirby
KirbySmith

Re: MATE GDM greeter theme testing and recovery

Post by KirbySmith »

Success in constructing a GDM variant greeter screen has been achieved. See thumbnail below. This is the low resolution image used by MDMsetup to distinguish the GDM greeter screens.

I will document the process as soon as I get time, including how to easily get an image of the screen before loggin in.

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Re: MATE GDM greeter theme testing and recovery

Post by Spearmint2 »

It's really great you accomplished what you wanted to. I suspect the HTML greeter is easier to construct since one can test at least see how it looks using a browser. Is Linux planning on leaving the GDM login method to the past soon? Is there some advantage (security?) of HTML over the GDM? I'm a bit curious why you wanted to do a GDM instead of the newer HTML type of login screen?
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Re: MATE GDM greeter theme testing and recovery

Post by KirbySmith »

The short answer is that the background image I wanted could be easily swapped with one in a greeter in the GDM greeter list, a greeter that had a suitable login box that I merely wanted to move to unobscure the block letters. There were very few HTML examples in the baseline greeter list that MDMsetup accesses. I don't know HTML and I thought figuring out the xml would be easier. As it happened, there were a few hiccups.

By the way, there is a method I'll document that I found on the web that makes getting a snapshot of the greeter much easier than the now obsolete historical methods for GDM greeters, so the advantage of a browser view with HTML is modest.

I know Clem is pushing for using HTLM5 so animated login greeter screens are feasible. I think that is a bigger project to undertake from my baseline than a GDM tweak. If I were interested in a built from scratch greeter, then HTML would likely be the way to go.

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Re: MATE GDM greeter theme testing and recovery

Post by Spearmint2 »

this is my current html themed login screen. Easily displayed as a webpage.

Picked up from this site.
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Re: MATE GDM greeter theme testing and recovery

Post by KirbySmith »

Assuming that is an animated image, did you have to upgrade MDM according to Clem's comments in that collection of links you posted in the earlier Newbie forum thread by Dr. McKay? If so, was there any conflict with anything that you noticed? As I wondered earlier, the development of capability for HTML5 starting in 2013 seems to require an MDM version that is significantly higher in number than the one supplied with Mint 17 in 2014. There must be a reason that Mint 17 was built with an earlier version.

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Re: MATE GDM greeter theme testing and recovery

Post by Spearmint2 »

I only have allowed the upgrades sent through the mintupdate tool. No conflicts I noticed.
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