Bash script using default value for empty parameter

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Problem

You have a bash script that accepts parameter(s) but you want to give a default value for a missing parameter.

Solution

For example you have a script that accepts a parameter with the year and month (ie 201703), but you want to give it a default of two months ago if the parameter is missing.

Bash script to add environment and date in Symfony appversion.yml file

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Problem

You are using CI/CD to deploy a Symfony application that has the appversion.yml configuration file, and you want to add the environment and a timestamp to it after deployment.

Solution

You can achieve this by creating and running a bash script like the following and passing the environment as a variable (ie script_name env) :

Error installing json 1.8.3 with ruby 2.4

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Problem

You are trying to install the gems for your rails application in a new computer, or by using ruby 2.4 and you get the following error:

Solution

Remove your old Gemfile.lock file and run bundle again. A newer version of json (ie 1.8.6) should be installed.

FATAL -> Failed to fork – Digital Ocean – Debian – Docker

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Problem

When you are trying to install a package inside a debian Docker container you get the following error message:

Solution

This is an indication of ‘out of memory’ so add a swap partition if it does not exist, on the host with the following:

(Thanks Valent)

Docker – Debian – Kernel panick – Automatic restart

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Problem

You have a remote server (Debian) running some Docker containers and you want to make sure that they all restart in the event of a kernel panick.

solution

  • Add an automatic restart after a kernel panick by running:

  • Emulate a kernel panick by running the following (SysRq more info here :

  • Check that the containers have restarted again with docker ps (NOTE: the containers should have been enabled to autorestart)

failed to execute ‘/lib/udev/socket:@/org/freedesktop/hal/udev_event’ ‘socket:@/org/freedesktop/hal/udev_event’

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Problem

Looking at your /var/log/syslog you see entries every few seconds like the following:

Solution

Seems that hal is not used in newer Ubuntu versions, so you can remove it:

Taken from the answer here