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Generate an RSA key pair

$ ssh-keygen -t rsa -b 2048 -C "email@example.com"

Output the public key in the PEM format

$ ssh-keygen -f ~/.ssh/id_rsa.pub -m PEM -e

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Sign a file using the private key

1. Sign a file input-file.txt and base64 encode it for sharing.

$ openssl dgst -sha256 -sign ~/.ssh/id_rsa input-file.txt | base64 > signb64.txt

Alternatively

$ openssl dgst -sha256 -sign ~/.ssh/id_rsa -out sign.sha256 input-file.txt
$ openssl base64 -in sign.sha256 -out <signature>

girishrau

1. Generate a dircolors file

$ dircolors -p > ~/.dircolors

2. Edit the ~/.dircolors to edit the OTHERS_WRITABLE entry. Switch the foreground and background colors. See colors here http://ascii-table.com/ansi-escape-sequences.php

OTHER_WRITABLE 32;40 # dir that is other-writable (o+w) and not sticky

Ref: https://unix.stackexchange.com/questions/94498/what-causes-this-green-background-in-ls-output

girishrau

Find the sizes of immediate subdirectories under the current directory

$ find ./ -maxdepth 1 -type d | xargs du -kh -d 1

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------------------------------------------
set echo off 
set serveroutput on
set timing off
set pages 25

column VAR_NAME format a50;
column VAR_TEXT_VALUE format a75;
column VAR_NUM_VALUE format 9999999999;
column TIMESTAMP format a33;

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List all stopped containers

docker ps -a -f status=exited

Delete all stopped containers

docker rm $(docker ps -a -f status=exited -q)

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$ git config --global merge.tool bc3
$ git config --global mergetool.bc3.path /bin/bcompare

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1. Generate the up to date grub configuration

$ grub2-mkconfig -o /boot/grub2/grub.cfg


2. Get the boot sequence of the kernels in the grub configuration

$ grep '^menuentry' /boot/grub2/grub.cfg

This will show the sequence in which the kernels are displayed