Flimm's questions

When I try to install a Flatpak from the Flathub website, I get a message like this one:

$ flatpak install flathub app.organicmaps.desktop
Looking for matches…
Remote ‘flathub’ found in multiple installations:

   1) system
   2) user

Which do you want to use (0 to abort)? [0-2]: 

I have several questions about this:

• What are the implications of choosing user over system? I'm interested in both security and usability.
• Do one or both require the use of sudo or admin privileges?
• How do I minimize the amount of disk space used? Should I consistently choose one or the other?
• Similarly, will my answer affect the download size?
• How can I list flatpaks that were installed under system and flatpaks that were installed under user? Can I migrate an installed package between them?
• Are they any Ubuntu-specific things I should know that would affect my choice?
• Can I configure flatpak to no longer ask me this question again in the future?

I'm troubleshooting some issues to do with multiple monitors and HiDPI on Wayland. I've learnt from online resources that applications on XWayland may not handle this use-case as expected. So now I want to know which applications are using XWayland, and which aren't.

How can I tell if an application is using XWayland or not?

Sometimes, I open an application and it opens a window that is too tall for my display. It also doesn't let me resize the window to make it less tall, and it doesn't have a maximize button. In Ubuntu (GNOME Shell), I can drag and drop the title bar to move the window, but I can't move the window higher than the top edge of the screen, which would have been useful to see the lower part of the window.

How do I find a workaround for windows that are too tall to fit in the display? Is there a way to force resize the window? Is there a way to move the window higher than the top edge of the monitor?

(An example of this issue: in VirtualBox, click File -> Import Appliance... The resulting window is too tall on some screen resolutions.)

I am interested in answers in GNOME Shell, as well as other environments.

apt-get and apt have a very useful option --verbose-versions (or -V for short) that shows you version numbers in its output. For instance:

$ sudo apt dist-upgrade --verbose-versions
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Calculating upgrade... Done
The following packages will be upgraded:
   firefox (53.0.3+build1-0ubuntu0.17.04.2 => 54.0+build3-0ubuntu0.17.04.1)
   firefox-locale-ar (53.0.3+build1-0ubuntu0.17.04.2 => 54.0+build3-0ubuntu0.17.04.1)
   firefox-locale-en (53.0.3+build1-0ubuntu0.17.04.2 => 54.0+build3-0ubuntu0.17.04.1)
   firefox-locale-es (53.0.3+build1-0ubuntu0.17.04.2 => 54.0+build3-0ubuntu0.17.04.1)
   firefox-locale-zh-hans (53.0.3+build1-0ubuntu0.17.04.2 => 54.0+build3-0ubuntu0.17.04.1)

How can I enable this option by default?

A relative of mine has recently sent me an email. He recently came across this alarming head-line from anti-virus vendor ESET:

KillDisk now targeting Linux: Demands $250K ransom, but can’t decrypt

The email goes on to describe a piece of software that encrypts the contents of the disk and demands a ransom.

My relative is alarmed and feels that surely an anti-virus is now needed.

I feel strongly that an anti-virus is not needed on Ubuntu. Rather, I feel that the best protection for an Ubuntu user is to install security updates promptly, to keep regular backups and to only install software from trusted sources like the Ubuntu Software Centre. Is that advice now out-of-date with the advent of KillDisk?

I'm trying to visit https://apps.ubuntu.com and to search for an app. However, it seems based on this screenshot, that this website only supports Ubuntu versions up to Ubuntu 14.04. Is this correct, or am I missing something?

Edit: karel correctly pointed out that although "Ubuntu 14.04 (trusty)" is listed in the search interface of apps.ubuntu.com, it doesn't do anything:

What is going on at apps.ubuntu.com?

On Docker's documentation pages, all example commands are shown without sudo, like this one:

docker ps

On Ubuntu, the binary is called docker.io. It also does not work without sudo:

sudo docker.io ps

How can I configure Docker so that I don't need to prefix every Docker command with sudo?

The Ubuntu installation disk has an option to install Ubuntu encrypted using LUKS. However, there is no option to perform an encrypted installation along-side existing partitions for a dual-boot scenario.

How can I install Ubuntu encrypted alongside another partition from the live disk?

If I attempt to change my password to nothing by opening "User Accounts", the "Change" button remains greyed out:

How do I change my password to be empty? I know you can set Ubuntu to automatically log you in, but I want my password to be empty, I never want to type in a password to authenticate myself as that user.

I know that there are reasons why this might not be a good idea, but I want to know if it is even possible. I'm using Ubuntu 12.10.

The typical workflow to install a Gsettings Schema is this:

1. Create a schema, with the extension .gschema.xml, with contents like this:

   <?xml version="1.0" encoding="UTF-8"?>
   <schemalist>
     <schema id="com.companyname.appname" path="/com/companyname/appname/">
         <key type="b" name="mybool">
             <default>false</default>
             <summary>Example summary</summary>
             <description>Example description</description>
         </key>
     </schema>
   </schemalist>
   

2. Copy the schema to /usr/share/glib-2.0/schemas/.

3. Compile the schema by running this command:

   sudo glib-compile-schemas /usr/share/glib-2.0/schemas/
   

However, writing to /usr/share/glib-2.0/schemas/ requires root privileges. Is there a way to install a schema to a non-global user directory?

After using Déjà Dup for a while, I keep getting this error after every attempt at a backup:

Backup location is too small. Try using one with more space.

Could I delete some backups made of certain dates only? For example, could I delete all backups older than a month?

My backup folder contains 372 files, with names like:

duplicity-full.20121122T124053Z.manifest.gpg
duplicity-full.20121122T124053Z.vol100.difftar.gpg
duplicity-full-signatures.20121122T124053Z.sigtar.gpg
duplicity-inc.20121122T124053Z.to.20121129T151249Z.manifest.gpg
duplicity-inc.20121122T124053Z.to.20121129T151249Z.vol1.difftar.gpg
duplicity-new-signatures.20121122T124053Z.to.20121129T151249Z.sigtar.gpg

Can I delete some of these files safely?

Déjà Dup allows me to choose whether to keep backups for six months, a year, or forever.

How do I choose to keep backups for less than six months, say, three months, or even more?

I have found an example of a schema that is referred two in two different ways, differing only in case, which is confusing to me.

Gsettings sees the schema name as com.canonical.Unity.Launcher, and does not accept com.canonical.unity.launcher as a valid schema name. On the other hand, dconf-editor only sees com.canonical.unity.launcher all lower-case, as seen in the screenshot.

If I change the key favorites in Gsettings, that change is reflected in dconf-editor, and vice-versa.

What's going on? Which is the correct schema name, com.canonical.Unity.Launcher, or com.canonical.unity.launcher?

Gsettings:

$ gsettings list-schemas | grep -i com.canonical.unity.launcher
com.canonical.Unity.Launcher
david@david-Aspire-5735:~$ $ gsettings list-recursively com.canonical.Unity.Launcher
com.canonical.Unity.Launcher favorite-migration '3.2.10'
com.canonical.Unity.Launcher favorites ['application://firefox.desktop', 'application://thunderbird.desktop', 'unity://running-apps', 'unity://expo-icon', 'unity://devices']
david@david-Aspire-5735:~$ gsettings list-recursively com.canonical.unity.launcher
No such schema 'com.canonical.unity.launcher'

dconf-editor:

I'm about to download Dungeon Defenders from the Humble Bundle website, and I am presented with two options: a .tar.bz2 tarball and a .mojo.run MojoSetup file.

Which should I choose? What are the benefits of a .mojo.run file? How easy is it to uninstall a MojoSetup file? How well integrated is it with Ubuntu?

I'm interested in hearing a general answer about .mojo.run files, the Dungeon Defenders game was just an example and not the core of my question.

Let's say I have a problem with my wireless connection. What commands should I run to share their output with a tech-savvy friend or an online support community?

For example:

• How can I tell if my wireless card is recognised?
• How can I get information on which wireless networks are within range?
• How can I tell if I am connected to a wireless, but not the Internet?

I'm asking this question because I'm seeing many questions about problems with wireless connections, without many details, like this one. It would be useful if I could point to this question so that the asker can improve their question with more information. I'm hoping for a comprehensive answer with all the details, or with links to other generic questions for brevity.

Canonical has recently announced Ubuntu for phones, which is Ubuntu with a specific interface for mobile devices.

Where can I get phones with this version of Ubuntu pre-installed? If no devices are available yet, where can I pre-order one?

How can I get a list of commands that have been installed with a particular package?

For example, if I install Chromium, what should type now? Or if I install moreutils, how do I know which commands have been installed?

There are several ways to install an application in Ubuntu:

• You can download a source tarball (generally a .tar.gz or a .tar.bz2 file) and install it manually. (See How do I install a .tar.gz (or .tar.bz2) file?)

• You can download a .deb file and install it manually, using dpkg or the Software Centre.

• You can search for the application in the Ubuntu Software Centre and install it there, or use apt with the official Ubuntu repositories.

• You can find a PPA or a third-party repo, and install it from there.

What are the pros and cons of each method? Please discuss security implications, frequency of updates and program reliability of each method in your answer.

I have noticed that different applications use different units, or mean different things by them.

For example, I have come across kB, KB, KiB, Kb and K. How many bytes do each of these units represent?

If there are different definitions for these units, which ones do which applications use?

Is there a way to download the Flash plug-in and the Microsoft fonts on one computer, and install them on another offline computer?

Simply downloading the flashplugin-installer and ttf-mscorefonts-installer packages isn't enough, as both these packages require Internet connections during their installation.

According to flashplugin-installer's description:

WARNING: Installing this Ubuntu package causes the Adobe Flash Player plugin to be downloaded from www.adobe.com. The distribution license of the Adobe Flash Player plugin is available at www.adobe.com. Installing this Ubuntu package implies that you have accepted the terms of that license.

And ttf-mscorefonts-installer has a similar warning:

You will need an Internet connection to download these fonts if you don't already have them.