Martin Drozdik's questions

Apparently apt-key is deprecated because its design contains a security risk.

The solution is to download the key and store it in a location writable only by the root and then to manually create a sources.list entry with the signed-by option.

For example, to install chrome we can do:

sudo wget -O- https://dl.google.com/linux/linux_signing_key.pub \
    | gpg --dearmor \
    | sudo tee /usr/share/keyrings/google-chrome.gpg >> /dev/null
echo deb [arch=amd64 signed-by=/usr/share/keyrings/google-chrome.gpg] \
    http://dl.google.com/linux/chrome/deb/ stable main \
    | sudo tee /etc/apt/sources.list.d/google-chrome.list >> /dev/null
sudo apt update
sudo apt install google-chrome-stable -y

The problem with this solution is that I cannot find the Dropbox signing key.

Dropbox help centre mentions a key for Fedora, but not Ubuntu:

https://linux.dropbox.com/fedora/rpm-public-key.asc

It all seems quite complicated. Are there some fool-proof, safe, non-deprecated ways to install Dropbox?

I have a fresh install with dual boot Windows and encrypted home directory and I am running into this problem. Anytime I disable the swap file in /etc/fstab my laptop loses the ability to suspend or to wake up from suspend.

It either fails to suspend - restarting instead, or becomes unresponsive after suspending, or the keyboard is not working.

Has anyone had similar problems? Any idea what can be going on?

When I use too much RAM on my Ubuntu 18.10, the GUI freezes. It stops reacting to keyboard and mouse and there is nothing to do other than hard reset the computer.

I believed that this was because the system has swapped out the Gnome binaries to disk and that, eventually, they would be swapped back. But this never happened in the observed timeframe (20 minutes or so).

I tried to solve the problem by disabling swapping (I prefer to lose unsaved work to losing unsaved work and having to restart the PC) and by instructing the OOM killer to kill whichever process has triggered the OOM situation according to this answer. However, this did not help. I tried to use a lot of memory by opening too many browser tabs and the only thing that happened was that the system became unresponsive again.

How is this possible? What other mechanism than thrashing could be involved? (genuine engineering question, not a rant)

I monitored the system stats during this experiment and it seems that the CPU was not running under 100% load, so it was not the computational constraint. Furthermore it seems that the GUI froze before I had the chance to open enough tabs to trigger the OOM killer.

The best theory that I can come up with is that the GUI libraries are using some sort of memory allocator that allows them to continue functioning even with very little memory, either by using some alternative swapping mechanism or by some CPU intensive heap rearrangements. Otherwise I have no clue.

Is there any better explanation for this behavior? Or a solution even?

EDIT

my swappiness:

vm.swappiness = 60

my memory:

martin@martin-UX305UA:~$ free -h
              total        used        free      shared  buff/cache   available
Mem:           7.7G        5.5G        145M        993M        2.1G        975M
Swap:          2.0G         57M        1.9G

my /etc/fstab

UUID=e0edf45b-903c-403f-b2c7-5e69b8b450da /               ext4    errors=remount-ro 0       1
# /boot/efi was on /dev/sda1 during installation
UUID=0564-1C88  /boot/efi       vfat    umask=0077      0       1
/swapfile                                 none            swap    sw              0       0

I have an Ubuntu 17.10 installation and I would like to connect two Nvidia GTX 1070 graphic cards and use the Nvidia official driver instead of the Nouveau drivers.

I have tested the following versions of the official drivers:

390.25
387.34
384.111

With each one I have no problems to boot up using a single graphics card, but with two I get stuck on the purple screen of death.

I tried to disable the purple screen so that I can diagnose the error, but I even failed at that.

I feel pretty much stuck in here, so any hints whatsoever are warmly welcome.

I have a very mysterious problem. Today, I was not able to log in. There was no "incorrect-password" message or anything, just the symptoms described in this question.

So I logged into the GUI-less shell and the first thing that shocked me was that when I hit tab, the bash auto-completion failed, because there was not enough space to create a temporary file. I was shocked, since I expected that about 90% of disk is still free. After removing some redundant docker volumes I was able to login and now I am trying to see where all my disk space went:

It seems that I have about 5 Giga of stuff in my home folder and another 5 is used by the system. This seems to correspond to reality. Since my disk is about 100 Giga I have nothing to worry about. However, df thinks otherwise:

Filesystem                   Size  Used Avail Use% Mounted on
udev                         3,9G     0  3,9G   0% /dev
tmpfs                        788M  9,9M  778M   2% /run
/dev/mapper/ubuntu--vg-root  102G   96G  847M 100% /
tmpfs                        3,9G   57M  3,8G   2% /dev/shm
tmpfs                        5,0M  4,0K  5,0M   1% /run/lock
tmpfs                        3,9G     0  3,9G   0% /sys/fs/cgroup
/dev/sda1                    464M  121M  315M  28% /boot
tmpfs                        788M  172K  788M   1% /run/user/1000
/home/askbe4/.Private        102G   96G  847M 100% /home/askbe4

Or more visually:

That is, the other tools show that I have only about 800 Megabytes free. This is a drastic difference. Also, it stands to mention that the disk and the home folder are both encrypted. I encrypted them just by clicking 'yes' during Ubuntu installation.

I feel completely dumbfounded and have no Idea what to make of this. Any hints are most welcome.

In other words, I would like to show the output not in the external console.

When I run my hello world program:

import std.stdio;
void main ()
{
    writeln("Hello world!"); 
}

The Application Output pane shows:

[Thread debugging using libthread_db enabled] Using host libthread_db library \"/lib/x86_64-linux-gnu/libthread_db.so.1\". [Inferior 1 (process 17025) exited normally]

Instead of the "Hello world!".

Some terminal window pops up for a fraction of a second, showing the "Hello world!" message, but then it disappears.

I tried to unset the "Run on external console" checkbox in the project options, but this doesn't seem to have any effect.

I tried to crawl through all the settings, but I did not find anything that would help.

I am trying to avoid this nasty bug in QtCreator 3.5.1.

https://bugreports.qt.io/browse/QTCREATORBUG-15291

I am quite sure that it is not present either in QtCreator 3.6.1 or in QtCreator 3.4.2. However I am not able to install either of them.

1. The online installers from Qt redirect me to 3.5.1.
2. The offline installers from Qt are only for 64bit Linux
3. I tried addning a PPA, then apt-get update upgrade, but nothing happened

Any guidance is well appreciated.

If I put an executable in ~/bin I can just type the first few letters of the filename and then hit tab to let the shell finish the rest of the name.

While this works with executable programs, it does not seem to work with shell scripts. Is this the desired behavior, or am I doing something wrong?

I would like to view the images for example from the oldest until the newest. This is not possible with many viewers I tried (Mirage, Shotwell, Gnome Image Viewer).

I read through all the related answers, but they do not apply to Ubuntu 14.04.

I have no .gnome2 folder and no Passwords and Encryption keys item in the system settings. I tried to crawl through every possible menu, but I could not find out how to do it.

The popup usually pops out when I start Chromium.

I recently made a fresh install of Ubuntu 14.04 and I noticed an item .gvfs in my home folder.

It is very strange, since it is visible even though it has a leading .

What is even stranger is that I cannot determine the owner of the file:

drwxrwxr-x  2 martin martin 4096 juil.  6 17:48 .gstreamer-0.10
d?????????  ? ?      ?         ?              ? .gvfs
-rw-rw-r--  1 martin martin   68 nov.  16  2013 .hgrc

EDIT:

I am sorry, I put my question too vaguely:

1. What is the purpose of this file/directory?
2. Why doesn't it contain any information in ls -la?
3. What does its presence and corruption tell about my system?
4. What should I do with it?
5. Why is it visible even with a preceding .?

EDIT2:

After reboot, the item disappeared.

The Synaptics package manager says that:

This package contains the shared library of libstdc++ compiled with debugging symbols.

But I can successfully print the contents of std members in the debugger without having this library. This is probably because most of them are templated, so the compiler can see the entire source code. But what good is a compiled library where the user cannot see the source code?

I am really confused. Please, could you explain?

I am trying to upgrade gcc-4.8.1 and g++-4.8.1 to 4.8.2. I added the PPA containing g++-4.8.2, ran apt-get update and then when I try:

martin@martin-Studio-1537:~$ sudo apt-get upgrade
[sudo] password for martin: 
...
The following packages have been kept back:
  cpp-4.8 g++-4.8 gcc-4.8 gcc-4.8-base libasan0 libatomic1 libgcc-4.8-dev
  libgcc1 libgcc1-dbg libgfortran3 libgomp1 libitm1 libquadmath0
  libstdc++-4.8-dev libstdc++6 libstdc++6-4.8-dbg
0 upgraded, 0 newly installed, 0 to remove and 16 not upgraded.

the packages I need to upgrade are kept back. When I try:

martin@martin-Studio-1537:~$ sudo apt-get dist-upgrade
...
The following packages will be REMOVED:
  g++-4.8 gcc-4.8
The following packages will be upgraded:
  cpp-4.8 gcc-4.8-base libasan0 libatomic1 libgcc-4.8-dev libgcc1 libgcc1-dbg
  libgfortran3 libgomp1 libitm1 libquadmath0 libstdc++-4.8-dev libstdc++6
  libstdc++6-4.8-dbg
14 upgraded, 0 newly installed, 2 to remove and 0 not upgraded.
Need to get 14.9 MB of archives.
After this operation, 32.4 MB disk space will be freed.

the system wants to remove g++-4.8 gcc-4.8.

When I try to install gcc-4.8 from Synaptic It wants to remove g++-4.8 and when I tell that it is ok to remove it, I get this error:

How can I install gcc-4.8.2 and g++-4.8.2?

EDIT:

As souravc suggested, I did

martin@martin-Studio-1537:~$ dpkg -l | grep "^rc" | awk '{print $2}'

and this is the result:

autoconf
bcmwl-kernel-source
dkms
lib64gcc1
libbotan-1.10-0
libc6-amd64
libc6-x32
libpcrecpp0:i386
libqt5clucene5:i386
libqt5declarative5:i386
libqt5designer5:i386
libqt5designercomponents5:i386
libqt5help5:i386
libqt5quickparticles5:i386
libqt5quicktest5:i386
libqt5script5:i386
libsigsegv2:i386
libx32gcc1
libx32stdc++6
linux-image-3.11.0-12-generic
linux-image-3.11.0-15-generic
linux-image-extra-3.11.0-12-generic
linux-image-extra-3.11.0-15-generic
usb-creator-gtk

I was trying to upgrade gcc-4.8.1 to gcc-4.8.2 using Synaptic from this PPA. The installation executed with no problem, but suddenly I had no gcc-4.8 at all. I was using gcc-4.7 and gcc-4.8 together, but only 4.7 is left for some reason. Then I tried to reinstall gcc-4.8 using apt-get install but I got unmet dependencies errors. I tried to solve this problem using the answers to this question, but to no avail.

sudo apt-get install gcc-4.8

results in:

...
The following packages have unmet dependencies:
 gcc-4.8 : Depends: binutils (>= 2.23.90.20131017) but
2.23.52.20130913-0ubuntu1 is to be installed
E: Unable to correct problems, you have held broken packages.

Here are the outputs of:

martin@martin-Studio-1537:~$ cat /etc/apt/sources.list
deb http://archive.ubuntu.com/ubuntu saucy main universe restricted multiverse
deb http://security.ubuntu.com/ubuntu/ saucy-security main universe restricted multiverse
deb http://archive.ubuntu.com/ubuntu saucy-updates main universe restricted multiverse
deb http://archive.ubuntu.com/ubuntu saucy-proposed main universe restricted multiverse
deb-src http://archive.ubuntu.com/ubuntu saucy main universe restricted multiverse #Added by software-properties
deb http://ppa.launchpad.net/ubuntu-toolchain-r/test/ubuntu saucy main

and

martin@martin-Studio-1537:~$ cat /etc/apt/sources.list.d/*
# deb http://download.mendeley.com/apt/ stable main
deb http://ppa.launchpad.net/p12/qtcreator/ubuntu saucy main
deb-src http://ppa.launchpad.net/p12/qtcreator/ubuntu saucy main
deb http://ppa.launchpad.net/p12/qtcreator/ubuntu saucy main
# deb-src http://ppa.launchpad.net/p12/qtcreator/ubuntu saucy main
deb-src http://ppa.launchpad.net/ubuntu-toolchain-r/test/ubuntu saucy main
deb-src http://ppa.launchpad.net/ubuntu-toolchain-r/test/ubuntu saucy main
# deb http://ppa.launchpad.net/webupd8team/y-ppa-manager/ubuntu saucy main
# deb-src http://ppa.launchpad.net/webupd8team/y-ppa-manager/ubuntu saucy main
# deb http://ppa.launchpad.net/webupd8team/y-ppa-manager/ubuntu saucy main
# deb-src http://ppa.launchpad.net/webupd8team/y-ppa-manager/ubuntu saucy main

I tried to repeat the suggestions in the answers after disabling all PPAs and then again with the gcc-4.8.2 PPA enabled and I still cannot install gcc-4.8.2.

What did I do wrong and how can I fix my system?

EDIT:

I tried

martin@martin-Studio-1537:~$ sudo apt-get install -f
[sudo] password for martin: 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.

and then

sudo apt-get update

but the result is the same.

I tried everything in this answer with the exception of purging or removing PPAs.

EDIT2:

I followed instructions from searchforgold6789's answer and it did work! I successfully installed gcc-4.8.1. But when I added the PPA again and tried to upgrade, I got the following output:

The following packages have been kept back:
  cpp-4.8 g++-4.8 gcc-4.8 gcc-4.8-base libasan0 libatomic1 libgcc-4.8-dev
  libgcc1 libgcc1-dbg libgfortran3 libgomp1 libitm1 libquadmath0
  libstdc++-4.8-dev libstdc++6 libstdc++6-4.8-dbg
The following packages will be upgraded:
  libcloog-isl4 libisl10
2 upgraded, 0 newly installed, 0 to remove and 16 not upgraded.

EDIT3:

When I do a apt-get dist-upgrade it suggests that g++-4.8 gcc-4.8 should be removed. Why is this so? Should I proceed? I think this was the reason I got into this trouble in the first place.

martin@martin-Studio-1537:~$ sudo apt-get dist-upgrade
...
The following packages will be REMOVED:
  g++-4.8 gcc-4.8
The following packages will be upgraded:
  cpp-4.8 gcc-4.8-base libasan0 libatomic1 libgcc-4.8-dev libgcc1 libgcc1-dbg
  libgfortran3 libgomp1 libitm1 libquadmath0 libstdc++-4.8-dev libstdc++6
  libstdc++6-4.8-dbg
14 upgraded, 0 newly installed, 2 to remove and 0 not upgraded.
Need to get 14.9 MB of archives.
After this operation, 32.4 MB disk space will be freed.

I have Ubuntu 13.10 on my laptop which I would like to use to connect to my Ubuntu 12.04 desktop. I installed the open ssh server on the desktop machine using:

sudo apt-get install openssh-server

I checked that the server is running:

sudo service ssh start

and I get:

start: Job is already running: ssh

Next I checked if there is a firewall using:

sudo ufw status

and I get:

Status: inactive

Next I found out the desktop's IP address by executing:

ip addr | grep inet

and I get:

inet 127.0.0.1/8 scope host lo
inet6 ::1/128 scope host 
inet 193.51.236.62/24 brd 193.51.236.255 scope global eth0
inet6 fe80::21a:a0ff:fe10:e8da/64 scope link 

So I suppose that 193.51.236.62 is my IP address.

Then on my laptop I verify that 193.51.236.62 is pingable and then I do:

ssh -v [email protected]

and I get:

OpenSSH_6.2p2 Ubuntu-6ubuntu0.1, OpenSSL 1.0.1e 11 Feb 2013
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug1: Connecting to 193.51.236.62 [193.51.236.62] port 22.

And nothing else seems to be happening. Please, how can I troubleshoot this problem? What am I doing wrong?

EDIT:

I can safely ping the server machine:

martin@martin-Studio-1537:~$ ping -c3 193.51.236.62
PING 193.51.236.62 (193.51.236.62) 56(84) bytes of data.
64 bytes from 193.51.236.62: icmp_seq=1 ttl=61 time=2.82 ms
64 bytes from 193.51.236.62: icmp_seq=2 ttl=61 time=4.05 ms
64 bytes from 193.51.236.62: icmp_seq=3 ttl=61 time=4.08 ms

--- 193.51.236.62 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2002ms
rtt min/avg/max/mdev = 2.823/3.653/4.082/0.587 ms

EDIT2:

I tried to diagnose the connection using nmap as suggested:

martin@martin-Studio-1537:~$ nmap 193.51.236.62

Starting Nmap 6.40 ( http://nmap.org ) at 2014-01-31 18:39 CET
Note: Host seems down. If it is really up, but blocking our ping probes, try -Pn
Nmap done: 1 IP address (0 hosts up) scanned in 3.06 seconds

and then:

martin@martin-Studio-1537:~$ nmap -Pn 193.51.236.62

Starting Nmap 6.40 ( http://nmap.org ) at 2014-01-31 18:40 CET
Nmap scan report for 193-51-236-62.lille.inria.fr (193.51.236.62)
Host is up (0.0056s latency).
Not shown: 998 filtered ports
PORT     STATE SERVICE
3128/tcp open  squid-http
8080/tcp open  http-proxy

Nmap done: 1 IP address (1 host up) scanned in 8.18 seconds

Recently my flatmate changed the maximum number of devices that can connect to our Wifi and since then I cannot see our Wifi network.

I am the only one in my household using Ubuntu. I logged into our rooter using a webbrowser and I can see other people's non-Ubuntu devices connected and working flawlessly. Their owners can see the wifi and can connect anytime. When I connect by cable, I can see my computer too, but it is not possible to connect wirelessly.

Here are the things I tried:

1. I checked that I am not blacklisted - I am not
2. I tried to "Connect to hidden Wifi network", entered SSID and password - no effect
3. I restarted the router multiple times - no effect

Please, what can be causing this and what can I do next?

EDIT:

I am using an Orange Livebox and here is a screenshot of the devices connected:

I tried to install Xubuntu 13.10 on an older computer. I noticed some difficulties during installation that may be relevant to my problems. Notably:

1. The screen resolution was extremely low. The windows were much larger than the screen and I had to move them around to get to the "Next" button.

2. The mouse cursor was a blur of colours that was flashing all the time.

The installation finished and I tried to reboot the computer. Immediately I got:

error: attempt to read or write outside of disk 'hd0'. 
Entering rescue mode... 
grub rescue>

I made a Boot Repair USB disk, booted it and chose the default repair. The application told me that the problem is repaired and that If this does not solve my problem I should show this link to someone who can help me.

What should I do next? I already tried to install Ubuntu and Xubuntu, both with no success.

EDIT:

I found a workaround.

1. Insert the Xubuntu live USB
2. Select "try Xubuntu"
3. In the settings menu select "install Xubuntu"

This fixed the problem for me. Since it is solved I cannot test the answer.

I have a very strange problem. Sometimes when I work a long time with my laptop while the desktop is hidden a strange thing happens. I show the desktop and it is all scrambled.

This problem is all the stranger since it happens only sometimes and I did not have it always.

How can I diagnose whether it is a hardware or software problem? Has anyone had similar symptoms?

EDIT:

This problem persists after upgrading to 13.10.

When the wallpaper gets scrambled and I change it to a different one and then back again, it seems fixed for a while. Does this fact indicate that it is not a hardware problem?

EDIT2:

Now this happens also for some windows, not just the desktop.

Apparently I am using Tex Live as my LaTeX distribution:

martin@martin-XPS-8300:~$ pdflatex -v

pdfTeX 3.1415926-2.4-1.40.13 (TeX Live 2012/Debian) kpathsea version
6.1.0 Copyright 2012 Peter Breitenlohner (eTeX)/Han The Thanh (pdfTeX). 
There is NO warranty.  Redistribution of this software is
covered by the terms of both the pdfTeX copyright and the Lesser GNU
General Public License. For more information about these matters, see
the file named COPYING and the pdfTeX source. Primary author of
pdfTeX: Peter Breitenlohner (eTeX)/Han The Thanh (pdfTeX). Compiled
with libpng 1.2.49; using libpng 1.2.49 Compiled with zlib 1.2.7;
using zlib 1.2.7 Compiled with poppler version 0.20.5

I would like to install additional packages using this guide.

They say:

With TeX Live manually installed, use tlmgr to manage packages individually.

tlmgr install <package1> <package2> ... 
tlmgr remove <package1> <package2> ...

But when I try:

tlmgr install algorithm2e

I get:

tlmgr: command not found

I also do not seem to have a ~/texmf folder, only a ~/.texmf-var folder. Is my installation corrupt or am I doing something wrong?

EDIT:

I found that I actually have a

/usr/local/share/texmf

EDIT2:

The command:

apt-cache policy texlive

results in:

texlive:
  Installed: 2012.20120611-5
  Candidate: 2012.20120611-5
  Version table:
 *** 2012.20120611-5 0
        500 http://jp.archive.ubuntu.com/ubuntu/ raring/main amd64 Packages
        100 /var/lib/dpkg/status

folder.

I am a noob with linux and I use Synaptic package manager to install all the software I need. I did so also for mathgl, the library for scientific graphs.

Recently a new version appeared online, but not in the package manager. I downloaded the sources and tried to install it manually. The instructions said:

cmake .
cmake .
make
make install

I did exactly the same, but then I realized that I forgot some build options. I did a web search to find a way how to uninstall the library, so that I can install it with the new settings, but I did not get a clear answer. What I found out is that when it comes to uninstalling under Linux, unless the developer provided an uninstall script, you are on your own and it is not trivial.

With this in mind I just tried to install the library without removing the misconfigured one.

cmake -D enable-all=on -D enable-langall=on .
cmake -D enable-all=on -D enable-langall=on .
make
make install

Everything seems to be fine. My question is this: is there any chance that the consequence of my action will come back to haunt me?

I am also concerned, because the old library was not removed as well as the old headers. Another strange thing is that the old headers are in

/usr/lib/mgl

while the new ones are in

/usr/local/lib/mgl2

Is there any explanation for this?