I have just installed Ubuntu MATE 21.10 and discovered two interesting packages which contain snapd in the name - gir1.2-snapd-1 and libsnapd-glib1:

$ dpkg -l | grep snapd
ii  gir1.2-snapd-1:amd64                     1.58-0ubuntu2                       amd64        Typelib file for libsnapd-glib1
ii  libsnapd-glib1:amd64                     1.58-0ubuntu2                       amd64        GLib snapd library

Both came from snapd-glib package.

Removal of them will ruin the system as follows:

$ sudo apt autopurge gir1.2-snapd-1:amd64 libsnapd-glib1:amd64
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following packages will be REMOVED:
  apturl* apturl-common* ayatana-indicator-sound* bluez-cups* cups* cups-browsed* cups-core-drivers* cups-daemon* cups-server-common*
  gir1.2-goa-1.0* gir1.2-snapd-1* hplip* hplip-data* libcanberra-pulse* libcupsimage2* libgutenprint-common* libgutenprint9* libhpmud0*
  libimagequant0* libpulsedsp* libsane-hpaio* libsbc1* libsnapd-glib1* libspeexdsp1* printer-driver-gutenprint* printer-driver-hpcups*
  printer-driver-postscript-hp* printer-driver-splix* pulseaudio* pulseaudio-module-bluetooth* pulseaudio-utils* python3-dateutil* python3-debconf*
  python3-olefile* python3-pil* python3-renderpm* python3-reportlab* python3-reportlab-accel* python3-software-properties* rtkit*
  software-properties-common* software-properties-gtk* ssl-cert* ubuntu-mate-core* ubuntu-mate-desktop* ubuntu-release-upgrader-gtk* update-manager*
  update-notifier* update-notifier-common*
0 upgraded, 0 newly installed, 49 to remove and 0 not upgraded.
After this operation, 49,3 MB disk space will be freed.
Do you want to continue? [Y/n] n
Abort.

Is it possible to remove gir1.2-snapd-1 and libsnapd-glib1 packages without ruining the system?

I have just installed fresh Ubuntu MATE 21.10 system.

Then I ran update-manager manually to check and get some new updates.

It showed a surprise for me - it will remove Firefox deb-package as shown on below screenshot to replace it with Snap:

Details of updates

• Install or remove
  • Duplicate packages to be removed
    • Firefox Web Browser

This is not acceptable for me, I want to use normal deb-package of Firefox.

Note: actually the result does not depend on online or offline installation, the first launch of update-manager will try to remove the Firefox deb-package.

Usually I'm avoiding snap-based applications, but sometime I need them.

For example - Markdown Lint Tool is shipped only as Snap named mdl.

It works great when files are in home folder -

$ echo "# header" > ~/test.md
$ /snap/bin/mdl ~/test.md ; echo $?
0

but it fails when file is located in /tmp directory:

$ echo "# header" > /tmp/test.md
$ cat /tmp/test.md
# header
$ /snap/bin/mdl /tmp/test.md
/snap/mdl/140/lib/ruby/gems/2.4.0/gems/mdl-0.9.0/lib/mdl/doc.rb:57:in `read': No such file or directory @ rb_sysopen - /tmp/test.md (Errno::ENOENT)
    from /snap/mdl/140/lib/ruby/gems/2.4.0/gems/mdl-0.9.0/lib/mdl/doc.rb:57:in `new_from_file'
    from /snap/mdl/140/lib/ruby/gems/2.4.0/gems/mdl-0.9.0/lib/mdl.rb:75:in `block in run'
    from /snap/mdl/140/lib/ruby/gems/2.4.0/gems/mdl-0.9.0/lib/mdl.rb:73:in `each'
    from /snap/mdl/140/lib/ruby/gems/2.4.0/gems/mdl-0.9.0/lib/mdl.rb:73:in `run'
    from /snap/mdl/140/lib/ruby/gems/2.4.0/gems/mdl-0.9.0/bin/mdl:10:in `<top (required)>'
    from /snap/mdl/140/bin/mdl:23:in `load'
    from /snap/mdl/140/bin/mdl:23:in `<main>'

For this particular application there are no options for snap connect:

$ snap connections | grep mdl
home                      mdl:home                             :home                                 -

Also I can't install it as classic:

$ snap install mdl --classic 
Warning: flag --classic ignored for strictly confined snap mdl

mdl 0.9.0 from Snapcrafters installed

What should I do to give Snap application full access to the /tmp folder?
Does it happen by Snap design or not?

It is known that Chromium browser is now shipped as deb "Transitional package - chromium-browser -> chromium snap".

But this maybe not expected for some users and they want to get normal deb-based version. How does this possible?

I have just installed the final version of Ubuntu 20.04 LTS desktop system from ubuntu-20.04-desktop-amd64.iso.
After two days of testing I completely do not like its graphical interface - the GNOME Shell.
Even installation of GNOME Flashback does not help either.

So I want to completely remove the GNOME Shell with all its trails from my system without re-installation.
Just want to start from scratch like it was approximately if I have installed Ubuntu from minimal network boot ISO.

For ScreenLets application I need to install libpng12-0 package on the Ubuntu 19.10 system.

I know that it is available only for Ubuntu 16.04 LTS.

So I have decided to download this package manually and install it by hand.

On previous Ubuntu versions (such as 18.04 LTS) this trick ends with success, but here on 19.10 it fails in very strange way:

wget http://mirrors.kernel.org/ubuntu/pool/main/libp/libpng/libpng12-0_1.2.54-1ubuntu1.1_amd64.deb
sudo apt-get install ./libpng12-0_1.2.54-1ubuntu1.1_amd64.deb

0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 0 B/116 kB of archives.
After this operation, 285 kB of additional disk space will be used.
Get:1 /home/user/libpng12-0_1.2.54-1ubuntu1.1_amd64.deb libpng12-0 amd64 1.2.54-1ubuntu1.1 [116 kB]
Selecting previously unselected package libpng12-0:amd64.
(Reading database ... 212864 files and directories currently installed.)
Preparing to unpack .../libpng12-0_1.2.54-1ubuntu1.1_amd64.deb ...
Unpacking libpng12-0:amd64 (1.2.54-1ubuntu1.1) ...

dpkg: error processing archive /home/user/libpng12-0_1.2.54-1ubuntu1.1_amd64.deb (--unpack):
 unable to install new version of '/lib/x86_64-linux-gnu/libpng12.so.0': No such file or directory
No apport report written because the error message indicates an issue on the local system
                                                                                         Errors were encountered while processing:
 /home/user/libpng12-0_1.2.54-1ubuntu1.1_amd64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)

What is wrong here? How can I get libpng12-0 installed on Ubuntu 19.10 system?

Note: the same happens on 19.04, but it is near EOL.

Let's assume that one has some HP printer and/or scanner and checked its support status on the corresponding page of HPLIP site - HP Developer Portal | All Supported Printer Models.

So one have the following information: the device Model name, Min. HPLIP Version and Driver Plug-in need.

What should one install to make Ubuntu fully support the HP printer and/or scanner?

I have just booted my clean Ubuntu 18.04 LTS VM and tried to install some application with sudo apt install.

But got error message:

E: Could not get lock /var/lib/dpkg/lock-frontend - open (11: Resource temporarily unavailable)
E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), is another process using it?

What process created the /var/lib/dpkg/lock-frontend file in Ubuntu?
How to gently stop it and take manual control on APT?

Let's assume that we are using Ubuntu 18.04 LTS (Bionic Beaver).

I know GUI ways to switch currently used APT mirror.

User should open Software & Updates (software-properties-gtk or software-properties-kde) and navigate to Ubuntu Software (Kubuntu Software) tab and then select mirror in Download from list:

But how to switch APT mirror from the commandline?

Notes/updates:

1. I need a solution without direct editing of /etc/apt/sources.list to prevent typos and automate correct mirror selection.
2. I need to switch mirror with one simple command as equivalent of picking one from Download from list in software-properties-gtk (also it is interesting where mirror addresses are saved in the system).
   3. I created discussion and poll named "Does Ubuntu need console alternative for software-properties-gtk / software-properties-kde?" on community.ubuntu.com.

I'm running Ubuntu 18.04 LTS with GNOME Shell.
Nautilus does not want to occupy 50% (left or right) of the screen sized at 1366x768.

Other applications (such as GNOME Terminal, Eye of GNOME, Gedit) are normally snapping to the left/right half of the screen.

But Nautilus can be resized to the width lower than half of screen (I can get 650 px, which is smaller than 1366/2 = 683 px).

The first usable screen resolution seems to be 1400x1050, then goes 1440x900. But large amount of current devices are still using 1366x768.

Is it just me?

Updates:
1. standard shortcut Super+← or Super+→ do not work too.
2. I reported bug 1801317 to launchpad which has linked upstream bug 411.
3. It does not work on GNOME FlashBack session too.

Introduction

I'm using Ubuntu MATE 16.04.5 LTS with latest 4.4 Linux kernel on several machines (laptops and desktops with USB 2.0 and USB 3.0).

For me it seems that something was changed inside USB driver internals of the kernel (or maybe udisks). Or USB flash hardware become cheaper and low-quality.

My USB flash has LED indicator. It is no-name gift (ChipsBank CBM2099E controller).

When I connect it to the computer - it has LED indicator on, it blinks when data is transferred.
My main idea: when I see blinking indicator I suppose that flash is busy, so I should not disconnect it to prevent data corruption.

Problem

Expected behavior

Many flashes - old Transcend JFV60, JF110, JF150, JF500, modern JF790; Kingston Data Traveller G2 and ADATA UE700, SanDisk Extreme Pro do not have such continuous blink problem. They stop blinking exactly after selecting Eject option and show bubble message that device is safe to remove:

Behavior of problematic flash

When I eject problematic USB flash drive from Caja file-manager or from GNOME Disks by pressing Eject menu option the flash LED is continuous blinking with fast rate. I tried to wait for about one hour, but is still blinks after this period of time. This happens even if I do not write anything on the drive. The notification bubble is not shown.

Question

My questions - what may be the reason of such blinking problem? Is it just me? Is it safe (for data) to disconnect such blinking flash?

Notes and updates

Notes

1. I do not ask here about slow drop of write cache and/or sync the drive. It highly depends on RAM size and on real write speed of the flash. The mentioned behavior exists in cases when no data were written.
2. All these flashes do not have problems with eject functionality on Windows. They get LED off just after clicking on Eject/Safely remove.
3. Selecting Power off this disk () in GNOME Disks forces flash to stop blinking, but I'm not sure about data safety in such case (for this particular flash; for other flashes and USB HDDs or SSDs it is safe, I know it).
4. I know that for example WD MyPassport USB hard-drives changes blink rate from fast to slow glow-fade after safely remove, but is other story as it have had spin-down and parked before, so it is safe to unplug it afterwards. So I do not think that the blinking of USB flashes indicate their polling and force user to detach it...

Updates

1. below is live output of tail -f /var/log/syslog

Nov 11 23:37:35 hostname kernel: [32596.101403] scsi 7:0:0:0: Direct-Access     General  UDisk            5.00 PQ: 0 ANSI: 2
Nov 11 23:37:35 hostname kernel: [32596.102526] sd 7:0:0:0: Attached scsi generic sg2 type 0
Nov 11 23:37:35 hostname kernel: [32596.104745] sd 7:0:0:0: [sdc] 31129600 512-byte logical blocks: (15.9 GB/14.8 GiB)
Nov 11 23:37:35 hostname kernel: [32596.107594] sd 7:0:0:0: [sdc] Write Protect is off
Nov 11 23:37:35 hostname kernel: [32596.107611] sd 7:0:0:0: [sdc] Mode Sense: 0b 00 00 08
Nov 11 23:37:35 hostname kernel: [32596.107792] sd 7:0:0:0: [sdc] No Caching mode page found
Nov 11 23:37:35 hostname kernel: [32596.107805] sd 7:0:0:0: [sdc] Assuming drive cache: write through
Nov 11 23:37:35 hostname kernel: [32596.109561]  sdc:
Nov 11 23:37:35 hostname kernel: [32596.110621] sd 7:0:0:0: [sdc] Attached SCSI removable disk
Nov 11 23:37:35 hostname udisksd[2294]: Mounted /dev/sdc at /media/username/FLASHDEVICE on behalf of uid 1000
Nov 11 23:37:52 hostname udisksd[2294]: Cleaning up mount point /media/username/FLASHDEVICE (device 8:32 is not mounted)
Nov 11 23:37:52 hostname udisksd[2294]: Unmounted /dev/sdc on behalf of uid 1000

note last lines here, at 23:37:35 device was unmounted/ejected from file manager, at 23:37:52 udisks removed it, but its LED still blinking.

2. Followed @WinEunuuchs2Unix ideas I tried both UDisks (legacy, it remains on my system because of upgrades from 12.04) and UDisks2 (modern and actual) to perform safely remove procedure - both

#udisks1 (legacy)
udisks --unmount /dev/sdc1 && udisks --detach /dev/sdc
#udisks2 (modern)
udisksctl unmount -b /dev/sdc1 && udisksctl power-off -b /dev/sdc

ended with same LED blinking problem with only one of my flashes.

3. Repeated the method above on my old Ubuntu 12.04.5 LTS and here LED is blinking on problematic flash. So it is a USB flash hardware issue.

Conclusion

There is some software-hardware incompatibility between my no-name ChipsBank CBM2099E based flash and Linux and/or Udisks. Other flashes (listed above in expected behavior) do not have problems.
^{In the Windows 8.1 running on the same laptop its safe removal is successful and LED is off.}

When I use search on Ubuntu 18.04 LTS with GNOME Shell I see the following icons among others:

How can I hide them? Are they hard-coded somewhere?

Note: this question is not duplicate of "How do I remove, log out, reboot and shut down from here?" asked today, as icons are black (not gray). It is logical continuation of it, but not duplicate.

Let's assume that one has some modern HP printer and/or scanner which is supported by HPLIP package from official repository. Or supported by newer version of HPLIP package (see this answer about installation).

From official documentation (HP Developer Portal | All Supported Printer Models) it is known that device needs proprietary/binary driver or plugin.

How should one install such plugin?

I have some software programmed in R using sf package, which require GDAL version >= 2.0.0.

But Ubuntu Xenial 16.04 LTS has only 1.11.3+dfsg-3build2.

How can I get GDAL version >= 2.0.0 on 16.04 LTS?

Let's assume that one has some modern HP printer and/or scanner which is not supported by HPLIP package from official repository.

Currently Ubuntu versions have the following versions in universe pocket:

bionic (18.04LTS): 3.17.10+repack0-5
focal (20.04LTS): 3.20.3+dfsg0-2
impish (21.10): 3.21.6+dfsg0-0ubuntu1

What can one do if printer is supported in newer version of HPLIP (checked this in HP Developer Portal | All Supported Printer Models)?

I have Ubuntu 18.04 LTS installed.

I inserted USB-flash to my laptop. It was automounted to /media/username/DISKLABEL and opened in Nautilus. I can read and write objects to it.

How can I access it from the application, which is installed as Snap?

I tried snaps of the following applications such as gedit, arduino-mhall119, organize-my-files. All them show me errors if I navigate to /media folder:

Could not read the contents of Media

Error opening the directory of '/media': permission denied

Output of active Snap interfaces is below:

$ snap interfaces  | grep -v ".*-$"
Slot                             Plug
:browser-support                 organize-my-files
:core-support                    core:core-support-plug
:cups-control                    gedit
:desktop                         gedit,organize-my-files
:desktop-legacy                  gedit,organize-my-files
:gsettings                       gedit,organize-my-files
:home                            arduino-mhall119,gedit,organize-my-files
:network                         arduino-mhall119,gedit,organize-my-files,pulsemixer
:opengl                          organize-my-files
:pulseaudio                      organize-my-files,pulsemixer
:unity7                          arduino-mhall119,gedit,organize-my-files
:wayland                         gedit
:x11                             arduino-mhall119,organize-my-files,pulsemixer
gnome-3-26-1604:gnome-3-26-1604  gedit
gtk-common-themes:gtk3-themes    gedit
gtk-common-themes:icon-themes    gedit
gtk-common-themes:sound-themes   gedit
-                                arduino-mhall119:serial-port
-                                gedit:avahi-observe
-                                gedit:mount-observe

Updates:

• connecting mount-observe to Gedit with snap connect gedit:mount-observe does not help.
• it seems that we need special Snap with support of removable-media interface.

On Ubuntu 16.04 LTS I have used simple keyboard shortcut to set property Always on Top (Nautilus window as example):

1. Alt+Space,

   

2. t

3. After next Alt+Space or right mouse click I see that window was set to Always on Top.

   

In standard Ubuntu 18.04 LTS with GNOME Shell I can press Alt+Space:

but it does not react to t.

Seems to be a real bug 1710421 since 17.10.

How to enable such menu accelerators/mnemonics in standard Ubuntu 18.04 LTS?

I have installed clean Ubuntu MATE 18.04 LTS and installed Scilab from repository here with

sudo apt-get update
sudo apt-get install scilab

After installation I tried to launch it from GUI (Applications → Other → Scilab) - it does not start.
Then I tried to launch it from terminal with scilab command. Terminal output is as follows:

$ scilab
/usr/bin/scilab-bin: error while loading shared libraries: libjava.so: cannot open shared object file: No such file or directory

so it can't find Java. I reported bug 1762999 about this problem.

I checked existence of libjava.so:

$ dpkg -S libjava.so  
openjdk-11-jre-headless:amd64: /usr/lib/jvm/java-11-openjdk-amd64/lib/libjava.so

so it is in place.

What should I do to get Scilab 6.0.1 working on Ubuntu 18.04 LTS?

As we know Arduino has non-official Snap which can access serial ports only if installed as classic (but not indicated in snap find output):

$ snap find arduino
Name                  Version  Developer  Notes  Summary
arduino-mhall119      1.8.5   mhall119   -      Arduino IDE

Arduino packages from repositories are outdated:

Package arduino

trusty (14.04LTS) (electronics): AVR development board IDE and built-in libraries [universe]
1:1.0.5+dfsg2-2: all
xenial (16.04LTS) (electronics): AVR development board IDE and built-in libraries [universe]
2:1.0.5+dfsg2-4: all
artful (electronics): AVR development board IDE and built-in libraries [universe]
2:1.0.5+dfsg2-4.1: all
bionic (electronics): AVR development board IDE and built-in libraries [universe]
2:1.0.5+dfsg2-4.1: all

According to official Arduino site the latest version of Arduino IDE is 1.8.9.

One can download IDE from official site, extract and install it with install.sh. Then when newer version will be released repeat this action. But it looks difficult and not user-friendly.

How can I get latest Arduino IDE installed in user-friendly way?

I'm running Ubuntu 17.10 on VM.

In the guest I opened GNOME terminal, launched Aptitude with sudo aptitude, then switched to the host machine to do some tasks.
When I returned to the Ubuntu guest it was showing this notification on lock screen:

Power
1 new notification

and after unlocking:

Automatic suspend
Computer will suspend very soon because of inactivity.

Just after unlocking Aptitude says that it can't download packages because the system is offline.

How can I disable this behavior?