Socrates's questions

Is there any way to set DEBIAN_FRONTEND=noninteractive when executing a script remotely via SSH?

Doing so I get this error:

sudo: sorry, you are not allowed to set the following environment variables: DEBIAN_FRONTEND

The reason I want to set DEBIAN_FRONTEND=noninteractive at exactly this place is because sometimes apt-get dist-upgrade shows a mask for some user interaction (whiptail). As want to run this script remotely via crontab -e there is no human to klick or press anything. Hence, I need to turn that off as the script would otherwise remain stuck.

The script I am trying to execute is located on server_one in /usr/local/bin/perform-update:

#!/bin/bash

sudo apt-get update
sudo DEBIAN_FRONTEND=noninteractive apt-get -y dist-upgrade
sudo apt-get -y autoremove
sudo snap refresh

I try to call it from server_two using this command:

SERVER_COMMAND="perform-update"
ssh -i $HOME/.ssh/id_rsa backupuser@server_one $SERVER_COMMAND

I have also set the appropriate rights for backupuser on server_one in sudo visudo:

backupuser      ALL=(ALL) NOPASSWD: /usr/local/bin/perform-update
backupuser      ALL=(ALL) NOPASSWD: /usr/bin/apt-get
backupuser      ALL=(ALL) NOPASSWD: /usr/bin/snap

Is there a standard way to set the order of multiple screens in Ubuntu 19.10?

I have used the "right click on the desktop" > "Display Settings" to set the order of my 3 screens. It works well after login to the system. But before the login the order is different to this setting here. Hence, my login window is not on the center screen and rather in my case on the right screen.

Is there a way to apply the same screen settings of the desktop to the screen settings of the login?

Is there a way to run sudo -E bash - without the sudo command?

I have the command curl -sL https://deb.nodesource.com/setup_13.x | sudo -E bash - that I want to run inside an Ubuntu container where no sudo exists. By running it with Docker though I provide the Docker parameter -u root:sudo so that everything inside executes as root.

The command sudo -E bash - fails though, because sudo does not exist. Is there a way to just run -E bash -?

Is there a way to set the sort order of the files and directories when using the ll command? I have two 16.04.5 servers with two ext4 drives. One folder exists on both drives containing the same files. When using ll on both servers the sort order is not the same (ls -l has the same result):

ll on server a:

Alex.txt
iBoy.txt
Immatriculation.txt
Radius.txt
WonderWoman.txt

ll on server b:

Alex.txt
Immatriculation.txt
Radius.txt
WonderWoman.txt
iBoy.txt

So the difference is the file iBoy.txt. Is there a way to figure out why this file is not located between Alex.txt and Immatriculation.txt like on server a?

EDIT 1:

As requested, here are the locales of both systems.

locale on server a:

LANG=de_DE.UTF-8
LANGUAGE=
LC_CTYPE="de_DE.UTF-8"
LC_NUMERIC=de_DE.UTF-8
LC_TIME="de_DE.UTF-8"
LC_COLLATE="de_DE.UTF-8"
LC_MONETARY=de_DE.UTF-8
LC_MESSAGES="de_DE.UTF-8"
LC_PAPER=de_DE.UTF-8
LC_NAME=de_DE.UTF-8
LC_ADDRESS=de_DE.UTF-8
LC_TELEPHONE=de_DE.UTF-8
LC_MEASUREMENT=de_DE.UTF-8
LC_IDENTIFICATION=de_DE.UTF-8
LC_ALL=

locale on server b:

locale: Cannot set LC_CTYPE to default locale: No such file or directory
locale: Cannot set LC_MESSAGES to default locale: No such file or directory
locale: Cannot set LC_ALL to default locale: No such file or directory
LANG=de_DE.UTF-8
LANGUAGE=
LC_CTYPE="de_DE.UTF-8"
LC_NUMERIC=de_DE.UTF-8
LC_TIME="de_DE.UTF-8"
LC_COLLATE="de_DE.UTF-8"
LC_MONETARY=de_DE.UTF-8
LC_MESSAGES="de_DE.UTF-8"
LC_PAPER=de_DE.UTF-8
LC_NAME=de_DE.UTF-8
LC_ADDRESS=de_DE.UTF-8
LC_TELEPHONE=de_DE.UTF-8
LC_MEASUREMENT=de_DE.UTF-8
LC_IDENTIFICATION=de_DE.UTF-8
LC_ALL=

Is there an easy way to transfer files between two SSH/SFTP servers? The perfect solution would be FileZilla, but it only lets you create a connection between local and remote, but not between remote and remote.

Theoretically I could open two Nautilus windows and connect to some ssh://server1/path/to/folder and ssh://server2/path/to/folder and then just pull the files from one to the other side. My experience is that this is very unstable. Transmitting files in size sum of i.e. 10MB is no problem, but transferring i.e. 10GB often resulted in Nautilus hanging itself up and remaining there in need of ps -e | grep nautilus -> kill -9 <pid>. I also tested the same thing with Nemo and Caja. While Nemo tends to be more stable than the two others, it still is not perfect and also breaks from time to time. FileZilla is extremely stable, never really got it to break, but it is not very flexible due to the mentioned fact that it can only connect to a single SSH server.

Of course I could also mount a folder with sshfs, but this is kind of an inconvenient solution. Too much pre-work to do to get a simple transfer running.

Is there any app that can handle transfers between two SSH servers without breaking? Perfect would be something like FileZilla, that picks up the job again if the connection got interrupted.

Is there any way to stretch a window using a keyboard shortcut to fullscreen or to the left half or right half within the MATE desktop environment? I am missing Super + Up or Super + Left.

Is there a way to measure the time spent in every single command within a bash file? Hence, put time in front of every command. The quantity of commands is unknown right now, as I intend to use this time measure for future bash scripts, too. And also worth mentioning is that I intend to only run simple bash scripts having command1, command2, command3, ... etc. Hence, no complex higher logic scripts.

Lets say I have a bash file similar to this one:

#!/bin/bash

mv /path/to/file /other/path/
cd /other/path/
tar -xzf /other/path/file

Is there a way to get some output similar to this?

 6.553s   mv /path/to/file /other/path/
 0.057s   cd /other/path/
19.088s   tar -xzf /other/path/file

I know that with time I can get the time spent of a single command. But I am looking for a solution for measuring the time of every command itself.

I am trying to figure out to turn off the function behind middle mouse button which inserts whatever text I have copied before into the document I click with that button. As the button of my mouse is quite sensitive I constantly insert text into my documents by accident when scrolling. I tried finding a solution in the unity-tweak-tool (0.0.7ubuntu2), but it appears not to have any setting to that. I found though a function for that in the gnome-tweak-tool (3.18.1-1) under keyboard and mouse > Insert by click with the middle mouse button. It just works sometimes and updates seem to revert this functionality. With sometimes I mean that some program react on turning off the insert functionality by it like gedit and others don't like the Chrome browser.

Is there any way to permanently turn of this text insert functionality of the middle mouse button?

Can someone tell me what terminal command the alias ll is for? All I can find online is many people saying that it is an alias for ls -l or ls -la or ls -ltr. But that's simply wrong. The result looks different. Is there any way to locate ll and look at its syntax?

Normally there is an SSH client that connects to an SSH server. The client then places commands that are executed on the server. Now, is there a way to do it the other way around? So that the client connects to the server, but the server also connects to the client and is able to execute commands on the client. Is that possible?

The reason I am looking for this is that I have two servers (A and B) in two different networks, both networks connected to the Internet. Server A can be accessed through port forwarding, but server B cannot. Since server A does all the work I'd like server B to connect to server A and just do whatever server A wants it to do.

Are reverse connections like this possible? Or maybe bidirectional SSH connections?

EDIT:

As an example I'd like to do the following. Being on server A and knowing that server B is SSH-connected to me, I'd like to connect to connect to server B and place a command like

echo "This is test content." > /home/myuser/mytestfile`

After that I'd like to find a file

/home/myuser/mytestfile

in server B.

I often use grep to find files having a certain entry like this:

grep -R 'MyClassName'

The good thing is that it returns the files, their contents and marks the found string in red. The bad thing is that I also have huge files where the entire text is written in one big single line. Now grep outputs too much when finding text within those big files. Is there a way to limit the output to for instance 5 words to the left and to the right? Or maybe limit the output to 30 letters to the left and to the right?

What protocol is used to reach computers by typing their names? For instance ping laptopone essentially finds the IP of the device and then pings it.

I used to have an AVM FritzBox 6360 as router / DHCP server within my network. Every device was reachable by its network name. Now I changed to a new box called ConnectBox and only half of my systems remain reachable:

myuser@systemone:~$ ping laptopone
ping: laptopone: Name or service not known

I assume that the AVM took the job of associating the DNS calls, basically associating the computer name to an IP address. The ConnectBox doesn't seem to do that job which means only some systems have the needed service running as daemon or process.

What type of service is needed on a system to enable it to answer to its name when there are network calls like ping or ssh?

How can I run an application with a specific Java version? I have three Java versions intstalled:

myuser@mysystem:~$ sudo update-alternatives --config java
There are 3 choices for the alternative java (providing /usr/bin/java).

  Selection    Path                                            Priority   Status
------------------------------------------------------------
  0            /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java   1081      auto mode
* 1            /opt/jdk-9.0.4/bin/java                          1         manual mode
  2            /opt/jdk1.8.0_162/bin/java                       1         manual mode
  3            /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java   1081      manual mode

I have Java 9 set as default and I'd like to keep it that way. Still, an application named pdfsam doesn't seem to work properly with Java 9. What command is necessary to run it with openjdk (option 3)?

Is there any open source application for Ubuntu/Linux that can handle SPARQL to perform queries over RDF stores and knowledge graphs? It doesn't necessarily have to be within apt, may as well be from another source. Any would do.

I have an application that I'd like to pack into DEB and RPM for making it installable into Linux distributions such as:

• Debian
• Ubuntu
• Linux Mint
• Fedora
• OpenSUSE

Do I need to develop an extra DEB file for Debian, Ubuntu and Linux Mint? Or does it suffice to create one for Debian that'll work for Ubuntu and Linux Mint, too?

What about RPM with Fedora and OpenSUSE?

I use Ubuntu 17.10 with KDE Plasma 5 installed and I'd like to show the frames per second. A simple counter of any kind would suffice. Is there any way of doing so?

I am looking for software that recognizes text within images. I tried out all of the tools mentioned here (gocr, fuzzyocr, libhocr0, ocrad, ocrfeeder, ocropus, tesseract-ocr, cuneiform). My input was a photograph of a printed document, hence not hand writing, just printed letters. Of all the tools, tesseract-ocr is the most accurate in my tests, but it still produces many many errors. Hence, scanning a document to some image file, and then continuing with indexing it or performing some NLP, sadly isn't an option. The error rate is too high.

So, given the age of the above mentioned posting, are there any better tools for extracting text from images or photographs?

EDIT 1:

With "image containing text" I mean, that I have a PNG/JPG/BMP file as a source and that I want to extract the pixelized text within it and have an ASCII/UTF-8 text as result and output.

Is there a special reason why the jitsi messenger is missing in 18.04 (and since 16.04) repositories?

It used to be in there with Ubuntu 14.04, but then was removed again. Are there issues with the software?

I was always very happy with Firefox and never felt the need to change to Chrome. But Adobe has stopped supporting Flash on Linux and Google has taken over this task. Though Google only supports its Flash for Chrome and not for Firefox.

Is it now necessary to change from Firefox to Chrome to enjoy safety and functionality regarding Flash?

I have a couple of webcams connected to my Ubuntu 14.04 server by USB. Now I would like to access them from my client (Linux, Mac, Windows). What would be the best way to do that? Are there any ready-to-use solutions for that in Ubuntu?