- 1)
% ssh-keygen -t rsa -b 4096 Generating public/private rsa key pair.
Enter file in which to save the key (~/.ssh/id_dsa): (just press Enter)
Enter passphrase (empty for no passphrase): (enter a passphrase and then press Enter or if you don't want want one just press Enter)
Enter same passphrase again: (repeat last action)
Your identification has been saved in ~/.ssh/id_rsa
Your public key has been saved in ~/.ssh/id_rsa.pub
The key fingerprint is:
A long string appears here
% - 2)
Paste the content of the ~/.ssh/id_dsa.pub file that just got generated on your local host into the file ~/.ssh/authorized_keys on the remote host and save. - 3)
Set proper permissions on your local host keys and .ssh directory:
chmod 700 ~/.ssh
chmod 644 ~/.ssh/id_rsa.pub
chmod 600 ~/.ssh/id_rsa
set proper permissions on your remote host authorized_keys and .ssh directory
chmod 700 ~/.ssh
chmod 644 ~/.ssh/authorized_keys
How to setup SSH private and public keys
How to find the 10 largest file or directories in Linux
This finds the largest 10 files :
find . -type f -print0 | xargs -0 du -s | sort -n | tail -10 | cut -f2 | xargs -I{} du -sh {}
This finds the largest 10 directories:
find . -type d -print0 | xargs -0 du -s | sort -n | tail -10 | cut -f2 | xargs -I{} du -sh {}
You can easily change -10 to -n where n is the number of files/directories you are trying to find.
Killing all processes containing a specific pattern in their process name
Say you want to kill all processes spawned from your Oracle Home. In Linux/Unix there is a nice command that lets you achieve this very easily.
If your Oracle Home is /u01/app/oracleHome then any oracle related process will have oracleHome in it's name. To kill all such processes at once issue the command :
pkill -9 -f oracleHome
If your Oracle Home is /u01/app/oracleHome then any oracle related process will have oracleHome in it's name. To kill all such processes at once issue the command :
pkill -9 -f oracleHome
How to extract values from a java properties files in a bash/shell script
Let's say you have a java properties (sample.prop ) file that contains this :
There are 3 parts to this task: 1) Getting the line that contains the value we want 2) extract the value from that line 3) store it in a variable to be used later in the script
To do part 1 we can simply grep for the value of the property we need :
For example :
To do part 2 we pipe the output of part 1 into awk for extraction of the value we need
the -F option of awk sets the delimiter to be '=' and then we print the second record which is what we need
Finally to store this value in a variable we do :
ORACLE_HOST=myhost.us.oracle.comNow, if we want to extract values from this properties file and use it in a shell/bash script for let's say an automation task, how do we go about that.
MW_HOME=/scratch/codrguy/sandbox
DB_HOST=dbhost.us.oracle.com
There are 3 parts to this task: 1) Getting the line that contains the value we want 2) extract the value from that line 3) store it in a variable to be used later in the script
To do part 1 we can simply grep for the value of the property we need :
For example :
grep ORACLE_HOST sample.prop
this returns
ORACLE_HOST=myhost.us.oracle.com
To do part 2 we pipe the output of part 1 into awk for extraction of the value we need
grep ORACLE_HOST sample.prop | awk -F= '{print $2}'
this returns
myhost.us.oracle.com
the -F option of awk sets the delimiter to be '=' and then we print the second record which is what we need
Finally to store this value in a variable we do :
my_value=$(grep ORACLE_HOST sample.prop | awk -F= '{print $2}')
Removing passphrase from a SSH key
If you have a SSH key and are tired of typing it over and over, there is an easy way to remove it.
Open a *nix terminal and type :
bash-3.2$ ssh-keygen -p
Open a *nix terminal and type :
bash-3.2$ ssh-keygen -p
Enter file in which the key is (/home/myuser/.ssh/id_rsa):
Enter old passphrase:
Key has comment '/home/myuser/.ssh/id_rsa'
Enter new passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved with the new passphrase.
How to receive or forward root emails in Linux
I find the following way the easiest way to manage who gets root's emails.
Open the file /etc/aliases for editing
Open the file /etc/aliases for editing
vi /etc/aliasesGo to the bottom of the file where you see something similar to :
# Person who should get root's mailChange marc to the email address of the user who should get the email and finally uncomment the line. So for example your last two lines of /etc/aliases should look like:
#root: marc
# Person who should get root's mailLast step is to issue the following command ro reload /etc/aliases
root: you@yourcompany.com
newaliase
How to take a Java thread dump from a shell/bash script
We already know how to get a Java thread dump manually. But what if we want to take a Java thread dump from a script to help us automate things.
To do this we need to come up with a ps and grep combination that will only return one result. so grep as many times as neccessary and/or use keywords that are only found in your process name so you only get one result.
Remember to add [] somewhere in your first grep so grep doesn't matches itself.
To do this we need to come up with a ps and grep combination that will only return one result. so grep as many times as neccessary and/or use keywords that are only found in your process name so you only get one result.
Remember to add [] somewhere in your first grep so grep doesn't matches itself.
output=$(ps -ef | grep m[y]ProcesseName )Then all you need to do is sending the QUIT signal to $2 which stores the PID of your process.
kill -QUIT $2So just add the above two lines to your script after modifying the first line to fit your needs and you should be good to go.
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