OZ1SEJ's questions

I have a 22.04 machine with an old-ish Nvidia GPU which worked perfectly until today, when I got a message that updates were available, and I chose to install them. Installation concluded successfully, and I got a message that a reboot was required. I clicked "Reboot now", and it rebooted. But after the reboot, the graphical desktop didn't load - all I had was a small cursor flashing in the top left corner.

The text terminals are available, though, but only at very low resolution. I can log in, and I have internet access. Lots of stuff about gdm-x-session in /var/log/syslog, but I'm not really into the nitty-gritties surrounding Ubuntu - I mainly just use it. So I'm at a loss - how to go about troubleshooting this?

For the record, I've now tried rebooting three times - same result.

I'm a little surprised that my fresh install of Ubuntu 21.10 can't play .mp4 files. This seems like a rather basic ability. Anyway, after getting very unhelpful errors in VLC, I installed the default GNOME player, totem, which gave me a more helpful error message: The necessary MPEG-4 AAV codec(s) is missing. But I fail to find any helpful info on where to get this. Not even here on askubuntu. What's going on?

I'm following this guide trying to use my Canon EOS 550D as a webcam. It is listed as supported by gphoto2.

So, I connected my Canon to my laptop using a USB-cable, and I had no problems running

$ sudo apt-get install gphoto2 v4l2loopback-utils v4l2loopback-dkms ffmpeg

and

$ sudo modprobe v4l2loopback exclusive_caps=1 max_buffers=2

I can also take a still photo using my Canon using this command

$ gphoto2 --capture-image-and-download

But then, when I try to run

gphoto2 --stdout --capture-movie | ffmpeg -i - -vcodec rawvideo -pix_fmt yuv420p -threads 0 -f v4l2 /dev/video0

I get this output:

$ gphoto2 --stdout --capture-movie | ffmpeg -i - -vcodec rawvideo -pix_fmt yuv420p -threads 0 -f v4l2 /dev/video0
ffmpeg version 4.2.4-1ubuntu0.1 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 9 (Ubuntu 9.3.0-10ubuntu2)
  configuration: --prefix=/usr --extra-version=1ubuntu0.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-nvenc --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
Capturing preview frames as movie to 'stdout'. Press Ctrl-C to abort.
[mjpeg @ 0x55cb3671a780] Format mjpeg detected only with low score of 12, misdetection possible!
Input #0, mjpeg, from 'pipe:':
  Duration: N/A, bitrate: N/A
    Stream #0:0: Video: mjpeg (Baseline), yuvj422p(pc, bt470bg/unknown/unknown), 1056x704, 25 tbr, 1200k tbn, 25 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (mjpeg (native) -> rawvideo (native))
[swscaler @ 0x55cb3678c5c0] deprecated pixel format used, make sure you did set range correctly

which is all to be expected, but it stops immediately with this error:

[video4linux2,v4l2 @ 0x55cb36720280] ioctl(VIDIOC_G_FMT): Invalid argument
Could not write header for output file #0 (incorrect codec parameters ?): Invalid argument
Error initializing output stream 0:0 -- 
Conversion failed!

And I really don't know where to go after this. Any help would be appreciated.

I downloaded the Arduino IDE v. 1.8.13 for Linux 64-bit. It's a zipped archive, which you unzip and run the binary. In order to have it easily accessible, I created a .desktop file in ~/.local/share/applications/ called arduino.desktop:

$ cat arduino.desktop 
[Desktop Entry]
Type=Application
Name=Arduino IDE
GenericName=Arduino IDE
Comment=Open-source electronics prototyping platform
Exec=/home/steen/Programmer/Arduino/arduino
Icon=/home/steen/.local/share/applications/arduino2.png
Terminal=false
Categories=Development;IDE;Electronics;
MimeType=text/x-arduino;
Keywords=embedded electronics;electronics;avr;microcontroller;
StartupWMClass=processing-app-Base

In order to have the Arduino logo displayed, I downloaded a PNG called arduino2.png and put it in the same folder, and referenced the above file to it, as you can see.

At approximately the same time, I also downloaded a program called SAOimage for astronomical imaging. I also had to create a .desktop file for this program:

$ cat saoimage.desktop 
[Desktop Entry]
Type=Application
Name=SAOImage DS9
GenericName=SAOImage DS9
Comment=Astronomical Fits File Editor
Exec=/home/steen/Programmer/SAOImage/ds9
Icon=/home/steen/Programmer/SAOImage/saoimage.png
Terminal=false
Categories=Graphics
MimeType=image/svg+xml;
Keywords=
StartupWMClass=processing-app-Base

Here, the icon file is in the same folder as the program. Now, when I press the super key and start typing "ard..." I see the Arduino icon, and it starts Arduino:

Likewise, when I press the super key and start typing "sao..." I see the SAOimage icon, and it starts SAOimage.

But once the programs are running, when I ALT+TAB between applications, Arduino is represented by the SAOimage icon, and SAOimage has no icon!

Also, if I first start SAOimage and then Arduino, they start in that order. But if I start Arduino first, and then press super key, type sao and start SAOimage, the program doesn't start; instead focus is just shifted to Arduino.

Why is this? Have I done something wrong? Is there some mechanism I don't understand? As far as I can see there is no reason - based on the .desktop files - that Ubuntu confuses the two...?

For some reason, my DNS seems to be set to 127.0.0.53. It's not really a problem, since my local (i.e. on my laptop) DNS seems to redirect DNS requests to the default gateway. But I would like it to not go that way. I suppose I must have installed some DNS server at some time in the past...

When I run $ nslookup, default server is always 127.0.0.53.

I found a post suggesting that I set DNSStubListener=no in /etc/systemd/resolved.conf, but this resulted in no DNS requests coming through. I could of course enter my default gateway manually, but then I would have to change it every time I brought my laptop to work.

Any suggestions?

EDIT: Adding the "hosts" line of /etc/nsswitch.conf:

hosts:          files mdns4_minimal [NOTFOUND=return] dns

I'm running a very old program, closed source, no longer updated, which has a horrible font. There's no option to change font in the program; can I somehow force that program to use another font? Example:

Alt+tab generally switches between windows, and I've found out that it works fine as long as the mouse pointer isn't in the middle of the screen. If it is, alt+tab switches to the last used window, but after half a second, it switches focus to the window, the mouse pointer is pointing at!

Am I the only one who finds that behavior extremely annoying? I mean, I know I can avoid that by parking my mouse above or below the alt-tab window line, but I fail to see how anyone could want this behavior.

This problem is reminiscent of this one from eight years ago, only it doesn't involve the mouse pointer. Is it really the same problem, or is this a different one?

I wanted the program Arduino to be accessible from the dash, so I put this in ~/.local/share/applications/arduino.desktop:

[Desktop Entry]
Type=Application
Name=Arduino IDE
GenericName=Arduino IDE
Comment=Open-source electronics prototyping platform
Exec=/home/username/Programmer/arduino/arduino
Icon=arduino
Terminal=false
Categories=Development;IDE;Electronics;
MimeType=text/x-arduino;
Keywords=embedded electronics;electronics;avr;microcontroller;
StartupWMClass=processing-app-Base

I have a transparent png icon (600 x 315 pixels) called arduino.png in the same directory, but it didn't work. It says here :

Application icons should be available at least at a resolution of 48x48 pixels. Place the icon in /usr/share/icons/hicolor/48x48/apps/

So I put it there, too, but I still don't have an Arduino icon associated with the desktop entry. How do I do this?

I recently installed 20.04 with proprietary Nvidia drivers. Today when I booted, the login screen was in 640x480, and so was the desktop when I logged in, and everything was extremely slow. Turns out the Nvidia driver was now replaced with the Noveau driver. Why and how did this happen, and how can I prevent it from happening again?

Some of the programs I use, like terminal programs, haven't been updated in years, so I am comfortable installing them with sudo apt install.

However, a great many programs, like Arduino, Stellarium, Inkscape, Steam, Kdenlive, etc. are updated frequently - if you install them from the Ubuntu software center or using sudo apt install, you get an ancient version. So I download the programs manually, often as an .AppImage file; this is actually often the recommended way.

This approach has two problems: 1. Programs aren't added to Dash, so I have to launch them from terminal or manually create .local/share/applications/*.desktop files; 2. Updating the programs is a manual process, and quite involved, if I also want to update the .local/share/applications/*.desktop files.

Is there a smart way to both have my programs update automatically and have them accessible from dash?

I downloaded GMAT and ran it according to the instructions:

$ ./GMAT-R2018a 
./GMAT-R2018a: error while loading shared libraries: libpng12.so.0: cannot open shared object file: No such file or directory

So I thought libpng was missing. So I downloaded, built and installed libpng 1.6.37 from source.

$ ./GMAT-R2018a 
./GMAT-R2018a: error while loading shared libraries: libpng12.so.0: cannot open shared object file: No such file or directory

So apparently I needed specifically version 1.2 of libpng, which I downloaded, built and installed from source:

$ ./GMAT-R2018a 
./GMAT-R2018a: error while loading shared libraries: libpng12.so.0: cannot open shared object file: No such file or directory

So apparently somehow GMAT couldn't see the file, so I made a symlink:

$ ln -s /usr/local/lib/libpng12.so.0 libpng12.so.0
$ ./GMAT-R2018a 
./GMAT-R2018a: error while loading shared libraries: libpng12.so.0: cannot open shared object file: No such file or directory

So I found a post somewhere saying that I should add a repository:

$ sudo add-apt-repository ppa:linuxuprising/libpng12
$ sudo apt update
$ sudo apt install libpng12-0

So now when I run GMAT, I get a new error:

$ ./GMAT-R2018a 
./GMAT-R2018a: /usr/local/lib/libpng12.so.0: no version information available (required by /home/steen/GMAT/GMAT/R2018a/bin/../lib/libwx_gtk2u_core-3.0.so.0)

And now I'm all out of ideas. Anyone?

Last night, my Ubuntu 19.04 suddenly became unresponsive, then on and off for a while. The fan started spinning rapidly, as a sign that much work was being done inside. I managed to start a system monitor, and the memory usage looked quite disturbing:

As you can see, my RAM filled up rapidly, invoking my swap partition, until both were full, at which point all memory seemed to be released, starting a new RAM-filling cycle.

I managed to reboot the machine, only to discover that the RAM eating started immediately again.

A top showed me that the offending process was tracker-extract, which I managed to uninstall, and after another reboot, no more RAM eating.

As it turned out, I had removed Nautilus in the process. sudo apt install nautilus installed tracker-extract again, but it has behaved itself since then.

Is this a known problem? Can I see somewhere what went wrong, so that I can prevent it from happening again?

I'm trying to install leandvb, but the GUI won't compile, because I (apparently) don't have X11 development libraries. How do I install these?

I have 19.04 on a Lenovo ThinkPad T580. When my laptop is not docked, default audio output device is "Speakers - built-in". But when I put my laptop in a docking station, it changes default audio output device to "Analog Output - ThinkPad Dock USB Audio".

I don't have any speakers connected to my dock, so I would like to continue to have audio out of the built-in speakers. Of course, I can just change it back manually every time I dock my computer, but it would be much nicer, if it just stopped changing default audio output device whenever I docked my computer.

Any ideas how to accomplish this?

In a default Ubuntu 19.04 - how often is computer time synchronized with time servers?

• Once every hour?
• Once every day?
• Something else entirely?

I've git cloned a program I need: https://github.com/dbdexter-dev/meteor_demod

When I try to compile it with make, I get a fatal error: ncurses.h: No such file or catalog

So I tried sudo apt install ncurses, but then I get Couldn't find package ncurses.

So i git clone https://github.com/millionbonus/ncurses.git, but when I make, it says no makefile found.

I've run out of ideas. Any help, please? :-)

I've used the GNOME method of linking my Google account, so that my files show up in Nautilus under "[email protected]". This works fine, as long as I stay in Nautilus. If I view the files in terminal, Filezilla, etc., all the file names are garbled:

Is there really no way to utilize the fact that I can access my Google Drive files from GNOME in other applications?

I have an employer-provided Google Drive account with almost 1 TB of data on. Basically everything I work on is on the Google Drive. It functions as a sort of live backup. Also, I'm running Ubuntu.

Now, back in the days on Windows, there was a Google Drive client that synced selected folders to my hard drive, which worked great, because I didn't have to wait for the client to download every single file when opening them.

Currently on Ubuntu, I'm using google-drive-ocamlfuse which is real steady, but extremely slow.

So I was thinking about using a syncing tool, e.g. unison, to sync files from my google-drive-ocamlfuse folder to a regular folder, so I can access files on the fly, but still have them uploaded to my Google Drive "live".

Is this a great idea, or a prescription for disaster?

I have a laptop with a 4k screen and an external HD screen. In the Ubuntu screen settings, I can choose 100% or 200% scaling, but only overall and not per screen. With 100%, text is way too tiny on my main display, and with 200%, it is way too large on my external display. Can't this be set individually per monitor?

Also, not all programs seem to respect the scaling setting. In GIMP, for example, text is okay, but icons are microscopic on my main 4k display.

I put an audio cd in the drive on my new 18.04 installation, started Rhythmbox, selected all and clicked "Extract". It extracted the first track and stopped. Whenever I try to rip more tracks, I get the message "Could not open resource for writing."

I tried to change the format to MP3, but then I'm told to install additional software, but not which software.

I tried to install Sound Juicer, and I should just have ripped my cd in Ogg Vorbis format, but I had to try and change the format to MP3, and now whenever I start Sound Juicer, I get a "Cancel or switch profile" dialog, but whatever I choose, Sound Juicer closes. I tried to uninstall it and install it again, but now that dialog comes up regardsless, and the program closes whatever I choose.