Trying to start the docker service after some upgrades fails with the following message:
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Failed to start docker.service: Unit is masked. |
It turns out that after upgrading or more specifically removing and then upgrading the docker installation in ubuntu (in this particular case in raspberry 4 with Ubuntu 20.04 installed), results in this error.
A search brings up the following:
https://forums.docker.com/t/failed-to-start-docker-service-unit-is-masked/67413
and from that the following bug post:
https://bugs.launchpad.net/ubuntu/+source/docker.io/+bug/1844894
So the solution is to run the following to be able to start the docker service (described in the first link above):
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sudo systemctl unmask docker sudo systemctl start docker |
To be able to get a more detailed information about your current linux distribution, including the code names use the following:
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kosmas:$ cat /etc/os-release NAME="Ubuntu" VERSION="18.04.5 LTS (Bionic Beaver)" ID=ubuntu ID_LIKE=debian PRETTY_NAME="Ubuntu 18.04.5 LTS" VERSION_ID="18.04" HOME_URL="https://www.ubuntu.com/" SUPPORT_URL="https://help.ubuntu.com/" BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/" PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy" VERSION_CODENAME=bionic UBUNTU_CODENAME=bionic |
There is a very nice example on the O’reilly ‘Linux Under The Hood’ training about using strace to compare performance of two commands that provide the same output but with different calls. The two different commands were: ls and echo *, that they both provide the listing of the current directory.
First using the strace with ls:
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kosmas:$ strace -c ls abi-4.13.0-45-generic config-4.4.0-31-generic initrd.img-4.4.0-31-generic System.map-4.15.0-123-generic vmlinuz-4.15.0-123-generic abi-4.13.0-46-generic efi memtest86+.bin System.map-4.15.0-124-generic vmlinuz-4.15.0-124-generic abi-4.4.0-31-generic grub memtest86+.elf System.map-4.15.0-126-generic vmlinuz-4.15.0-126-generic config-4.13.0-45-generic initrd.img-4.13.0-45-generic memtest86+_multiboot.bin System.map-4.4.0-31-generic vmlinuz-4.4.0-31-generic config-4.13.0-46-generic initrd.img-4.13.0-46-generic retpoline-4.13.0-45-generic vmlinuz-4.13.0-45-generic vmlinuz-4.4.0-31-generic.efi.signed config-4.15.0-123-generic initrd.img-4.15.0-123-generic retpoline-4.13.0-46-generic vmlinuz-4.13.0-45-generic.efi.signed config-4.15.0-124-generic initrd.img-4.15.0-124-generic System.map-4.13.0-45-generic vmlinuz-4.13.0-46-generic config-4.15.0-126-generic initrd.img-4.15.0-126-generic System.map-4.13.0-46-generic vmlinuz-4.13.0-46-generic.efi.signed % time seconds usecs/call calls errors syscall ------ ----------- ----------- --------- --------- ---------------- 15.81 0.000095 12 8 write 14.64 0.000088 7 12 mprotect 13.48 0.000081 5 17 mmap 9.98 0.000060 7 9 openat 7.82 0.000047 4 11 close 7.32 0.000044 22 2 getdents 6.82 0.000041 6 7 read 5.66 0.000034 3 10 fstat 4.99 0.000030 4 8 8 access 3.16 0.000019 10 2 2 statfs 2.00 0.000012 12 1 munmap 1.83 0.000011 4 3 brk 1.66 0.000010 5 2 ioctl 1.50 0.000009 5 2 rt_sigaction 0.67 0.000004 4 1 rt_sigprocmask 0.67 0.000004 4 1 arch_prctl 0.67 0.000004 4 1 set_tid_address 0.67 0.000004 4 1 set_robust_list 0.67 0.000004 4 1 prlimit64 0.00 0.000000 0 1 execve ------ ----------- ----------- --------- --------- ---------------- 100.00 0.000601 100 10 total |
And using the same with echo *
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kosmas:$ strace -c echo * abi-4.13.0-45-generic abi-4.13.0-46-generic abi-4.4.0-31-generic config-4.13.0-45-generic config-4.13.0-46-generic config-4.15.0-123-generic config-4.15.0-124-generic config-4.15.0-126-generic config-4.4.0-31-generic efi grub initrd.img-4.13.0-45-generic initrd.img-4.13.0-46-generic initrd.img-4.15.0-123-generic initrd.img-4.15.0-124-generic initrd.img-4.15.0-126-generic initrd.img-4.4.0-31-generic memtest86+.bin memtest86+.elf memtest86+_multiboot.bin retpoline-4.13.0-45-generic retpoline-4.13.0-46-generic System.map-4.13.0-45-generic System.map-4.13.0-46-generic System.map-4.15.0-123-generic System.map-4.15.0-124-generic System.map-4.15.0-126-generic System.map-4.4.0-31-generic vmlinuz-4.13.0-45-generic vmlinuz-4.13.0-45-generic.efi.signed vmlinuz-4.13.0-46-generic vmlinuz-4.13.0-46-generic.efi.signed vmlinuz-4.15.0-123-generic vmlinuz-4.15.0-124-generic vmlinuz-4.15.0-126-generic vmlinuz-4.4.0-31-generic vmlinuz-4.4.0-31-generic.efi.signed % time seconds usecs/call calls errors syscall ------ ----------- ----------- --------- --------- ---------------- 0.00 0.000000 0 1 read 0.00 0.000000 0 1 write 0.00 0.000000 0 5 close 0.00 0.000000 0 4 fstat 0.00 0.000000 0 6 mmap 0.00 0.000000 0 4 mprotect 0.00 0.000000 0 1 munmap 0.00 0.000000 0 3 brk 0.00 0.000000 0 3 3 access 0.00 0.000000 0 1 execve 0.00 0.000000 0 1 arch_prctl 0.00 0.000000 0 3 openat ------ ----------- ----------- --------- --------- ---------------- 100.00 0.000000 33 3 total |
So the difference in time is 0.00000 for the echo and 0.000601 for the ls.
Similarly the number of calls for the echo is 33, but ls is using 100.
To install megtools (command line utilities for Mega.nz), in your raspberry with ubuntu installed follow the steps below (thanks to the instructions from here: https://www.instructables.com/id/Descarga-archivos-de-Mega-con-Raspberry-Pi/)
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sudo apt-get -y install build-essential libglib2.0-dev libssl-dev libcurl4-openssl-dev libgirepository1.0-dev |
You may also need to add some additional packages if there is an error about the documentation.
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wget https://megatools.megous.com/builds/megatools-1.10.3.tar.gz |
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tar xvfz megatools-1.10.3.tar.gz cd megatools-1.10.3 ./configure make sudo make install sudo ldconfig |
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[Login] Username = my_mega@email Password = mypassword |
To install the latest/current versions of erlang (23.0.2) and elixir (1.10.3), follow the instructions below:
Install asdf ( full instructions https://asdf-vm.com/#/core-manage-asdf-vm):
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git clone https://github.com/asdf-vm/asdf.git ~/.asdf --branch v0.7.8 |
Add the following two lines in your ~/.bashrc file:
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# Add asdf version manager . $HOME/.asdf/asdf.sh . $HOME/.asdf/completions/asdf.bash |
Reload/Source your bash file with
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source ~/.bashrc |
Install the erlang plugin
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asdf plugin add erlang |
If you get the following warnings:
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... Extracting source code Building Erlang/OTP 23.0.2 (asdf_23.0.2), please wait... WARNING: It appears that a required development package 'libssl-dev' is not installed. WARNING: It appears that a required development package 'automake' is not installed. WARNING: It appears that a required development package 'autoconf' is not installed. WARNING: It appears that a required development package 'libncurses5-dev' is not installed. Configure failed. ... |
Install the missing packages:
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sudo apt install libssl-dev automake autoconf libncurses5-dev |
Install latest erlang version:
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asdf install erlang latest ... Erlang/OTP 23.0.2 (asdf_23.0.2) has been successfully built ... |
Set it up globally (if you want):
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asdf global erlang 23.0.2 |
Add elixir plugin:
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asdf plugin add elixir |
Install latest elixir version (1.10.3):
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asdf install elixir latest |
Set it up globally:
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asdf global elixir 1.10.3-otp-23 |
Finally you can also install the latest Phoenix version (1.5.3):
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mix archive.install hex phx_new 1.5.3 |
After installing an image of the Ubuntu server on the Raspberry 4, the wifi is not automatically configured after the initial book.
In order to be able to use the WiFi follow the steps described below for setting up your wifi in your SD card, and then reboot your raspberry (make sure that the indentation in the yaml file is correct, and also your WiFi access point is enclosed in quotes):
https://ubuntu.com/tutorials/how-to-install-ubuntu-on-your-raspberry-pi#3-wifi-or-ethernet
