Linux Authentication and Access - A different approach

A small briefing that covers the basic points of creating a new user in a Linux host. We start with a simple username/password old and insecure authentication method and then we add RSA certificate to make the user authentication modern and more robust. In the second section, we copy the private key to our windows machine and we configure windows PuTTY so that we connect to the Linux server using RSA certificates.

In the second part of the article, we make a very short introduction to Chef Technology and how this can be used in order to automate user provisioning on a host. This example does exactly the same user provisioning operations shown in the first part but this time with Chef.

In the last section we introduce we introduce a simple Jenkins pipeline that demonstrates the use of the sftp and ssh commands for the linux user we previously created. 

Just 10 minutes reading.

Read the full article here:

https://github.com/illumine/articles/blob/master/Linux-Admin-School/Create-and-Delete-Users-SSH-from-Windows.md

My Linux Shell Cook-Book

How many times we struggle ourselves to remember how to write correctly a for loop in shell ?
When was the last time we did a search for string comparison in bash and test for a file timestamp?

My favourite treatment for weak memory or "shell syntax blackouts" is a simple text file called
MyBashCooks.txt which takes proudly always the first tab in Notepad++ when I am coding scripts.

I think it is void to mention that this small file is hand on the web and travels with me when I am visiting clients, generally, it is one of the very few things I have handy and don't move a second step without it.

The recipes in my cookbook share a common secret: single command line, so you can use them on the command prompt as is or break them in several lines inside your scripts.

I think we say too much on this, please enjoy and if you find a mistake, please drop me a line:

# If then else in a single line

r=ee; if [ "$r" == "" ] ;  then  echo "is null" ; else  echo "not null"; fi

# If then else ARITHMETIC Operations

x=0;if [ $x -eq 0 ]; then echo "x=0";else echo "other"; fi

# Check if word belongs to string and if it does, run a shell command 
# Compatible with all shells

string="this is a string "; word="str";test "${string#*$word}" != "$string" && echo "$word found in $string"

# Negative of the previous

string="this is a string "; word="xxx";test "${string#*$word}" != "$string" || echo "$word not found in $string"

# Combined case of found and not found....

string="this is a string "; word="xxx";test "${string#*$word}" != "$string" && echo "Executes when found." || echo "Executes when NOT found."

# single line while loop

while true; do  echo '----'; sleep 1 ; done

while true; do top -b -n 1  |  egrep  'top|Tasks|Cpu|Mem|Swap|PID|mysql' | grep -v root   ;sleep 10; echo '----' ; done

# single line for loop

for h in {app0,app1,app2,app3,index0,index1,index2,index3};  do echo $h; sleep 1;  done

# Tests the existence  of word in a string: works in all POSIX shells (bash, dash, korn...) 

string="my name is MyBighrase";word="e i"; echo "search [$word] in [$string]";test "${string#*$word}" != "$string" && echo "$word found in $string"

# From UNIX timestamp to date:

echo 1365436826 | gawk '{print strftime("%c", $0)}'

# From Date to timestamp:

date --date='04/04/2013 20:30:01' +"%s"

# Format Date output

date +"%m-%d-%y"

# Search for a string across directories with grep

find -RH theString /this/directory

# Serach for line numbers and cut a file only from line to line:

this one searches for all line numbers with date 20130607

cat  slow.log | grep -n 130607  

we get the lines of this date exists and isolate those numbers in a new file.

cat  slow.log | sed -n '16582739,17369638p' > slow_20130607.txt

# Monitoring Linux Processes

while true ; do top -b -n 1 -p 2163 >> mysql_3000.txt ; sleep 15 ;  done &

while true ; do date >> tmpfs_3000.txt ; df -h | grep mysql ; sleep 15 ;  done >> tmpfs_3000.txt &

while true ; do date >> process_3000.txt;  echo "show full processlist;" |  mysql -uroot -pmypass | grep -v Sleep >> process_3000.txt  ; sleep 15 ; done &