[RFI] Adding the docker repo's GPG key to the system.

[TriMoon]

Problem description

• apt-key(8)

  
  Note that if usage of apt-key is desired the additional installation of the GNU Privacy Guard suite packaged in gnupg) is required.
  For this reason alone the programmatic usage (especially in package maintainer scripts!) is strongly discouraged.

• Current apt expects keys from packages to be put inside /etc/apt/trusted.gpg.d
  • binary keys ending in .gpg
  • ASCII-armored keys ending in .asc

Problem location

File: https://docs.docker.com/install/linux/docker-ce/ubuntu/#set-up-the-repository

• ubuntu.md#L114 (and maybe other documentation also) instructs to download the docker repo's gpg key, which is actually an ASCII-armored file, and pipe it into apt-key which is deprecated on modern systems.
• ubuntu.md#L153-L156 and similar lines.

Suggestions for a fix

1. The apt-key command should not be used in the instructions.
2. The recommended command to retrieve the gpg-key should be changed into:
   (As a single command-line)
   sudo curl -LR https://download.docker.com/linux/ubuntu/gpg -o /etc/apt/trusted.gpg.d/docker.gpg.asc
   • Notes:
     1. The -fsS flags to curl should not be used so the user has visual feedback and can retry in case of failures.
     2. The time-stamp of the source is used for the output file to aid in version checking.
     3. The output is put into a file under /etc/apt/trusted.gpg.d ending in .asc to indicate an ASCII-armored key to apt.
3. The recommended command to check that the key is properly installed should be changed into:
   apt-key list docker
4. The recommended command(s) to set up the "stable" repository should be changed into:

   > printf "%s %s %s %s %s\n" \
   	"deb" \
   	"[arch=amd64]" \
   	"https://download.docker.com/linux/ubuntu" \
   	"$(lsb_release -cs)" \
   	"stable" \
   	> /tmp/docker.list
   > sudo install \
   	--mode=a=r,u+w \
   	/tmp/docker.list \
   	/etc/apt/sources.list.d
   > rm /tmp/docker.list

Related reports

#1218, #8298, #9373, #10285, and maybe #10333?

[TriMoon]

Just a followup with results of running sudo apt install docker-ce after the setup done above:

Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 docker-ce : Depends: containerd.io (>= 1.2.2-3) but it is not installable
             Recommends: aufs-tools but it is not going to be installed
             Recommends: cgroupfs-mount but it is not going to be installed or
                         cgroup-lite but it is not going to be installed
             Recommends: pigz but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

Which means the package containerd.io can not be found on the default repos of ubuntu 19.10. Not even with the ppa enabled...
There is however a package named containerd available via universe
So we are unable to install as-is at moment...

My system info:

> neofetch --stdout
OS: Ubuntu 19.10 x86_64 
Model: Manual build Rev:xxx 
Mainboard: X99-PRO/USB 3.1 Rev 1.xx (ASUSTeK COMPUTER INC.) 
Bios: 2017-08-10 AMI Ver:3801 
Kernel: 5.3.0-40-generic 
Uptime: 17 hours, 57 mins 
Packages: 2795 (dpkg), 9 (snap) 
Shell: zsh 5.7.1 
Resolution: 1680x1050 @ 59.88Hz, 2560x1080 @ 60.00Hz 
DE: KDE 
WM: KWin 
Theme: Breeze [KDE], Adapta-Nokto [GTK2], Default [GTK3] 
Icons: breeze [KDE], breeze [GTK2/3] 
Terminal: vscode 
Font: [KDE], Noto Sans, 10 [GTK2/3] 
Locale: en_US.UTF-8 
Memory: 4428MiB / 32026MiB (13%) �[37m[--=============�[37m] 
CPU: Intel i7-5820K (12) @ 4.0GHz [44.0°C] 
GPU: NVIDIA GeForce GTX 1080 Ti 
GPU Driver: NVIDIA 430.50 
CPU Usage: 2% 
Disk (/): 18G / 146G (13%) 
Disk (home): 27G / 63G (45%) 
Disk (efi): 89M / 511M (18%) 
Disk (efi-other): 5.4M / 549M (1%) 
Disk (Data): 551G / 3.5T (17%) 

[docker-robott]

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