asdf and terraform (or vault or packer)

Posted on 7 April 2021 by kosmas

Using the asdf version manager to manage versions of various binaries like terraform, vault or packer is easily done by following the instructions below:

Download and install asdf if you haven’t got it already (https://asdf-vm.com/#/core-manage-asdf)
If you want to install the latest version of terraform for example do the following:

asdf plugin add terraform
asdf install terraform latest
asdf global terraform 0.14.9
asdf list
terraform
  0.14.9
terraform --version
Terraform v0.14.9

				
					
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						asdf plugin add terraform
asdf install terraform latest
asdf global terraform 0.14.9
asdf list
terraform
  0.14.9
terraform --version
Terraform v0.14.9

					

			

Renaming multiple files in linux

Posted on 18 March 2021 by kosmas

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Problem

You would like to rename multiple files, replacing some text with something else (like replacing Pixies_The with Pixies).

Solution

Install the rename utility

sudo apt install rename

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						sudo apt install rename

and replace the text as follows

cd folder_to_rename_files
rename 's/Pixies_The/Pixies/g' **

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						cd folder_to_rename_files
rename 's/Pixies_The/Pixies/g' **

Get/Set platform information

Posted on 15 March 2021 by kosmas

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To get or set in environment variables the platform information of a system you can use the following:

export ARCH=$(case $(arch) in x86_64) echo -n amd64 ;; aarch64) echo -n arm64 ;; *) echo -n $(arch) ;; esac)
export OS=$(uname | awk '{print tolower($0)}')

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						export ARCH=$(case $(arch) in x86_64) echo -n amd64 ;; aarch64) echo -n arm64 ;; *) echo -n $(arch) ;; esac)
export OS=$(uname | awk '{print tolower($0)}')

Taken from the installation instructions of the Operator SKD here: https://master.sdk.operatorframework.io/docs/installation/

Linux disabling a service on bootup

Posted on 12 February 2021 by kosmas

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To stop having a service automatically start after bootup in a Linux system with systemctl use the following to stop and then disable the service:

sudo systemctl stop service_name
sudo systemctl disable service_name

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						sudo systemctl stop service_name
sudo systemctl disable service_name

Failed to start docker.service: Unit is masked

Posted on 27 January 2021 by kosmas

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Problem

Trying to start the docker service after some upgrades fails with the following message:

Failed to start docker.service: Unit is masked.

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						Failed to start docker.service: Unit is masked.

Solution

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):

sudo systemctl unmask docker
sudo systemctl start docker

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						sudo systemctl unmask docker
sudo systemctl start docker

Getting detailed information about your Linux distribution

Posted on 16 December 2020 by kosmas

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To be able to get a more detailed information about your current linux distribution, including the code names use the following:

kosmas:$ cat /etc/os-release
NAME=&quot;Ubuntu&quot;
VERSION=&quot;18.04.5 LTS (Bionic Beaver)&quot;
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME=&quot;Ubuntu 18.04.5 LTS&quot;
VERSION_ID=&quot;18.04&quot;
HOME_URL=&quot;https://www.ubuntu.com/&quot;
SUPPORT_URL=&quot;https://help.ubuntu.com/&quot;
BUG_REPORT_URL=&quot;https://bugs.launchpad.net/ubuntu/&quot;
PRIVACY_POLICY_URL=&quot;https://www.ubuntu.com/legal/terms-and-policies/privacy-policy&quot;
VERSION_CODENAME=bionic
UBUNTU_CODENAME=bionic

				
					
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						kosmas:$ cat /etc/os-release
NAME=&quot;Ubuntu&quot;
VERSION=&quot;18.04.5 LTS (Bionic Beaver)&quot;
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME=&quot;Ubuntu 18.04.5 LTS&quot;
VERSION_ID=&quot;18.04&quot;
HOME_URL=&quot;https://www.ubuntu.com/&quot;
SUPPORT_URL=&quot;https://help.ubuntu.com/&quot;
BUG_REPORT_URL=&quot;https://bugs.launchpad.net/ubuntu/&quot;
PRIVACY_POLICY_URL=&quot;https://www.ubuntu.com/legal/terms-and-policies/privacy-policy&quot;
VERSION_CODENAME=bionic
UBUNTU_CODENAME=bionic

					

			

Displaying timestamps in dmesg output

Posted on 10 December 2020 by kosmas

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If you would like to be able to see the dmesg output with timestamps instead of time in seconds since booting up, use the -T like:

dmesg -T | less

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						dmesg -T | less

Using strace for analyzing performance

Posted on 6 December 2020 by kosmas

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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:

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

				
					
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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 *

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

				
					
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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.

Linux – prevent command line input appearing in history

Posted on 18 August 2020 by kosmas

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Problem

You would like to type some sensitive information in the command line (password, key), but you don’t want this to appear in the history.

Solution

Add a single space before the start of the command.

restarting X Window Server from command line in linux

Posted on 2 June 2020 by kosmas

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To restart your X Window Server from the command line in linux, without affecting any non-graphical programs (but losing any unsaved information in your graphical user interface programs), you can use the following:

sudo systemctl restart display-manager

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Web notebook about thoughts and discoveries in DevOps, SRE, Software Engineering….

Tag Archives: linux

asdf and terraform (or vault or packer)

Renaming multiple files in linux

Get/Set platform information

Linux disabling a service on bootup

Failed to start docker.service: Unit is masked

Problem

Solution

Getting detailed information about your Linux distribution

Displaying timestamps in dmesg output

Using strace for analyzing performance

Linux – prevent command line input appearing in history

Problem

Solution

restarting X Window Server from command line in linux