Mads Skjern's questions

From other sources I have read that "most package managers are selfish", including APT and PIP, and they cant be expected to work well together. Therefore one should try to stick to either PIP or APT.

I know that all packages that I installed manually have been installed with PIP. But I assume that some may have been installed by APT as dependencies. When I install some random application via APT, and this application needs a few Python packages, how are they (typically) installed?

• Are they installed as APT-packages, with no PIP
• Are they installed with PIP, maybe even in a virtualenv?
• Does APT maybe even have some PIP-understanding and then it uses PIP as a tool to install Python packages?

My reason for asking this

I am trying to somehow clean up in my Python packages, because something got broken, and I am trying to get a better understanding of how things work so I don't break it even more. There are several packages that I cant figure out if I installed manually or if they have been installed as dependencies behind the scenes.

The top printer in the list is at a club I used to go to. That printer has been taken down at least a month ago. The second printer on the list is at work.

Currently I am connected to the wifi hotspot on my cell phone, and still both printers are shown as "Ready".

First of all, I would like to know what that means? Is this the expected behavior? I would expect something like "Not available".

Furthermore, if I try to delete these printers, they disappear from the list, and then reappear after approximately 5 seconds.

If I actually do connect the the network at work, and then try to print, the job gets added to the queue but then nothing more happens.

What is going on?

Ubuntu Version

Distributor ID: Ubuntu 
Description:    Ubuntu 20.04.2 LTS 
Release:    20.04
Codename:   focal

The following line shows the the four partition table entries of 16 bytes each. See here for a specification of the format.

$ sudo hd ubuntu-16.10-desktop-amd64.iso -s 446 -n 64
000001be  80 00 01 00 00 5e e0 ff  00 00 00 00 00 80 2f 00  |.....^......../.|
000001ce  00 fe ff ff ef fe ff ff  54 24 2f 00 c0 12 00 00  |........T$/.....|
000001de  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
000001fe

The latter three are all zeros, while the first entry is the interesting one. Byte 0 (counting from 0) has value 0x80 which means that it does in fact describe "an active partition". Byte 4 describes the partition type, fx 0x0B is FAT32. However 0 is an invalid value. According to this source:

00 : -- Should NOT be used in an actual table entry! It does not indicate an unknown type, but rather an empty entry; in which case, all other fields in that 16-byte entry should be zero-filled as well.

So according to what I can read, the MBR data is invalid. What is going on?

I did this with Ubuntu 16.04 (Yakkety), downloaded via this link, and the file has md5sum 3f50877c05121f7fd8544bef2d722824.

I got this number using:

jdoe@jdoe:~$ sudo hdparm -tT /dev/sda
/dev/sda:
 Timing cached reads:   9260 MB in  2.00 seconds = 4633.30 MB/sec
 Timing buffered disk reads: 978 MB in  3.00 seconds = 325.77 MB/sec

The SSD is a Samsung 850EVO with SATA 6Gb/s (750MB/s). The laptop is an Asus S200E, which I believe also is SATA 6Gb/s.

Arent they talking about the cache on the disk? Or is it a cache on the motherboard itself?

I have made a number of graphical mockups in SVG, and then exported them to PNG. They all have transparent background, because that makes sense in my case.

However, it isn't easy to browse through the PNG-files. Both Gwenview and Gnome Image Viewer (aka eog, Eye of Gnome) show the background as gray checkered. Chrome shows it how I like it, but it can't really browse through images, whereas Gwenview shows the next image on a right arrow click.

Is there an image viewer that let's me browse through SVG / PNG and show the background as fx white? Or another solution to my problem?

Gwenview and Gnome Image Viewer

Chrome Browser

Error to begin with, can't boot

I had to do a hard reboot of my computer, and when booting up it (initramfs I think) gave an error:

mount: mounting /dev/mapper/ubuntu--vg-root on /root failed: Invalid argument
mount: mounting /dev on /root/dev failed: No such file or directory
mount: mounting /sys on /root/sys failed: No such file or directory
mount: mounting /proc on /root/proc failed: No such file or directory 

Target filesystem doesn't have requested /sbin/init.
No init found. Try passing init= bootarg. 

Trying to mount from Live-CD

I have very, very important data on it, so instead of trying to fix the boot system (or whatever I should call it), I would just like to mount it and copy the important files to a USB stick.

I have tried several guides without luck. The most straight forward seems to be Mount encrypted volumes from command line?. Here is what I've done:

ubuntu@ubuntu:~$ sudo cryptsetup luksOpen /dev/sda3 myvolume
Enter passphrase for /dev/sda3: 
ubuntu@ubuntu:~$ mkdir mountpoint
ubuntu@ubuntu:~$ sudo mount /dev/mapper/myvolume m
mount: unknown filesystem type 'LVM2_member'
ubuntu@ubuntu:~$ sudo mount -t ext4 /dev/mapper/myvolume mountpoint
mount: /dev/mapper/myvolume already mounted or mountpoint busy

The mountpoint folder is not busy, it's an empty folder that I can delete if I want. I believe /dev/mapper/myvolume is not mounted, well since I have not done it, and since the following returns nothing ubuntu@ubuntu:~$ mount -l | grep myvolume.

I don't know what information is relevant for the question. In my struggle I have learned the names of dozens of new commands, and it would be too much text to post the information from all of them. So please tell me what additional information is relevant.

Output of blkid

/dev/loop0: TYPE="squashfs" 
/dev/sda1: UUID="04BD-5CB0" TYPE="vfat" 
/dev/sda2: UUID="4b4af9b9-1290-431a-bfcb-3b8e24d52c54" TYPE="ext2" 
/dev/sda3: UUID="09e172eb-1080-4f68-80fb-1386ac0491b6" TYPE="crypto_LUKS" 
/dev/sdb1: UUID="369D-508C" TYPE="vfat" 
/dev/mapper/myvolume: UUID="0DkUPe-3S13-zNOA-5wi0-uzPb-CCB8-9m14C1" TYPE="LVM2_member" 
/dev/mapper/ubuntu--vg-swap_1: UUID="44b26e6d-cb85-4949-b0e8-9421ab515d03" TYPE="swap" 

Complete summary from Ubuntu Boot-Repair

I did not try to restore anything, I only used the tool to print a summary of relevant information. Tool used: https://help.ubuntu.com/community/Boot-Repair

Result: https://www.jottit.com/gvwbu/ (many pages)

I need the handbrake-cli tool, and I believe it does not come with the standard Ubuntu repository, so I followed this guide.

Adding the repository

sudo apt-get install ubuntu-restricted-extras
sudo apt-get install libdvdread4
sudo /usr/share/doc/libdvdread4/install-css.sh
sudo apt-get install python-software-properties
sudo apt-add-repository ppa:stebbins/handbrake-snapshots
sudo apt-get update

No errrors, everything seems fine.

Everything seems fine through the installation:

jdoe@jdoe:~$ sudo apt-get install -y handbrake-cli handbrake-gtk 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following extra packages will be installed:
  libjansson4
The following NEW packages will be installed:
  handbrake-cli handbrake-gtk libjansson4
0 upgraded, 3 newly installed, 0 to remove and 3 not upgraded.
Need to get 16.6 MB of archives.
After this operation, 36.5 MB of additional disk space will be used.
Get:1 http://dk.archive.ubuntu.com/ubuntu/ trusty/universe libjansson4 amd64 2.5-2 [25.2 kB]
Get:2 http://ppa.launchpad.net/stebbins/handbrake-snapshots/ubuntu/ trusty/main handbrake-cli amd64 7352svnppa1~trusty1 [5,705 kB]
Get:3 http://ppa.launchpad.net/stebbins/handbrake-snapshots/ubuntu/ trusty/main handbrake-gtk amd64 7352svnppa1~trusty1 [10.8 MB]
Fetched 16.6 MB in 5s (2,930 kB/s)        
Selecting previously unselected package libjansson4:amd64.
(Reading database ... 247827 files and directories currently installed.)
Preparing to unpack .../libjansson4_2.5-2_amd64.deb ...
Unpacking libjansson4:amd64 (2.5-2) ...
Selecting previously unselected package handbrake-cli.
Preparing to unpack .../handbrake-cli_7352svnppa1~trusty1_amd64.deb ...
Unpacking handbrake-cli (7352svnppa1~trusty1) ...
Selecting previously unselected package handbrake-gtk.
Preparing to unpack .../handbrake-gtk_7352svnppa1~trusty1_amd64.deb ...
Unpacking handbrake-gtk (7352svnppa1~trusty1) ...
Processing triggers for gnome-menus (3.10.1-0ubuntu2) ...
Processing triggers for desktop-file-utils (0.22-1ubuntu1) ...
Processing triggers for bamfdaemon (0.5.1+14.04.20140409-0ubuntu1) ...
Rebuilding /usr/share/applications/bamf-2.index...
Processing triggers for mime-support (3.54ubuntu1.1) ...
Processing triggers for hicolor-icon-theme (0.13-1) ...
Setting up libjansson4:amd64 (2.5-2) ...
Setting up handbrake-cli (7352svnppa1~trusty1) ...
Setting up handbrake-gtk (7352svnppa1~trusty1) ...
Processing triggers for libc-bin (2.19-0ubuntu6.6) ...

But afterwards only some documentation is installed

jdoe@jdoe:~$ handbrake
The program 'handbrake' is currently not installed. You can install it by typing:
sudo apt-get install handbrake
jdoe@jdoe:~$ handbrake-gtk
The program 'handbrake-gtk' is currently not installed. You can install it by typing:
sudo apt-get install handbrake
jdoe@jdoe:~$ handbrake-cli
handbrake-cli: command not found

jdoe@jdoe:~$ locate handbrake
/etc/apt/sources.list.d/stebbins-handbrake-snapshots-trusty.list
/etc/apt/trusted.gpg.d/stebbins-handbrake-snapshots.gpg
/etc/apt/trusted.gpg.d/stebbins-handbrake-snapshots.gpg~
/usr/share/app-install/desktop/handbrake:ghb.desktop
/usr/share/doc/handbrake-cli
/usr/share/doc/handbrake-gtk
/usr/share/doc/handbrake-cli/AUTHORS
/usr/share/doc/handbrake-cli/CREDITS
/usr/share/doc/handbrake-cli/NEWS.gz
/usr/share/doc/handbrake-cli/README.Debian
/usr/share/doc/handbrake-cli/THANKS
/usr/share/doc/handbrake-cli/changelog.gz
/usr/share/doc/handbrake-cli/copyright
/usr/share/doc/handbrake-gtk/changelog.gz
/usr/share/doc/handbrake-gtk/copyright
/var/cache/apt/archives/handbrake-cli_7352svnppa1~trusty1_amd64.deb
/var/cache/apt/archives/handbrake-gtk_7352svnppa1~trusty1_amd64.deb
/var/lib/apt/lists/ppa.launchpad.net_stebbins_handbrake-snapshots_ubuntu_dists_trusty_Release
/var/lib/apt/lists/ppa.launchpad.net_stebbins_handbrake-snapshots_ubuntu_dists_trusty_Release.gpg
/var/lib/apt/lists/ppa.launchpad.net_stebbins_handbrake-snapshots_ubuntu_dists_trusty_main_binary-amd64_Packages
/var/lib/apt/lists/ppa.launchpad.net_stebbins_handbrake-snapshots_ubuntu_dists_trusty_main_binary-i386_Packages
/var/lib/apt/lists/ppa.launchpad.net_stebbins_handbrake-snapshots_ubuntu_dists_trusty_main_i18n_Translation-en
/var/lib/dpkg/info/handbrake-cli.list
/var/lib/dpkg/info/handbrake-cli.md5sums
/var/lib/dpkg/info/handbrake-gtk.list
/var/lib/dpkg/info/handbrake-gtk.md5sums

And another question

Why is handbrake-cli not included in the handbrake package from the default Ubuntu repository? Perhaps, there is a really good reason for that, that I should know :)

I know of java.com/verity, but it only tells me the the version number of Java, e.g.

Your Java version: Version 8 Update 25

It does not tell me whether I have OpenJDK or Oracle installed. Is there another online service that does tell this?

If I disconnect my external monitor, simply by unplugging the HDMI connector, Ubuntu seems to think it is still there. Windows stay there, and and if I open new windows they are shown there, ie I cant see them!

Is there a way to fix this?

I run Ubuntu 14.04 Trusty Tahr.

I have a webcal url, something like webcal://myservice.com/foobar. When my "Windows friends" click on such a link in their browsers, or paste the url into the address bar, there is an open dialogue, where they can choose Outlook.

What is the equivalent on Ubuntu? I have installed Thunderbird, and then the Lightning extension. But I can't find a way of adding the webcal/ical url from within Thunderbird/Lightning, and Firefox does not offer opening the link in Thunderbird.

It does offer opening it with "30 Boxes". Apparently this is a webservice, which is somehow offline today, and therefore I can't use it.

Please let me know the easiest way of opening this webcal/ical thing, to see what appointments and stuff is in there.

During Ubuntu installation (13.04 I believe):

The text says:

Connecting this computer to a wi-fi network allows you to install
third-party software, download updates, automatically detect your 
timezone, and install full support for your language. 

Does this make any sense? Was it supposed to show available networks, but somehow shows smth different?

If not, what is going on then, and what is the password for my wireless network interface card?

I created a USB-stick with Ubuntu, using the recommended tool "Startup Disk Creator" and the image for Ubuntu 13.10. The very simple interface looks like this:

There can't be much to misunderstand in this GUI. I have chosen to create a USB stick with a live version of Ubuntu, which will save files and settings from session to session, on the USB drive, right?

Well, it just doesn't save anything. I go in, create a file on Desktop, restart and it's gone.

I did the whole procedure three times, i.e. first creating the USB, then testing if I could save.

Have I misunderstood something?

I need to save some information about the current partitioning of my hard drive.

I already did

fdisk -l > file.txt

GParted tells a bit more information (label, size, used). Is it possible to make GParted save this information to a file?

According to Wikipedia's article on the address resolution mechanism of DNS there should be a "hint file" in my OS somewhere, containing IP addresses of a few "root name servers".

How do I see this hint file on Ubuntu?