Get external IP address from Linux Shell / Command Line (CLI)

The simplest way to get your external IP from linux shell or from linux command line is to use the following command:


wget http://ipecho.net/plain -O - -q ; echo


Once executed you should simply get an output like this:

123.124.125.126

If you don't have wget installed yet you can install it like this:

apt-get update; apt-get install wget

Feed in your ssh password into Linux SSH command to login automatically

I needed to login to a linux server automatically, but without using Shared RSA Key. I needed to simulate a human being typing password, but to do that automatically so I can use it inside my shell scripts.

Surprisingly this solution was difficult to find on Google. I would like to share this simple technique in hope this will save somebody long research time.

This is an alternative solution from login into SSH using Shared RSA Key technique which is much more secure and the recommended method.

WARNING: This method exposes your ssh login / password! (use with caution)

Install sshpass if you don't have it yet:

apt-get update
apt-get install sshpass

Example shell script:

#!/bin/bash

sshpassword=mypassword

sshpass -p $sshpassword ssh 192.168.1.1 "ls -l"

iPhone Mail IMAP setup with iRedMail Server not working via SSL (SOLVED)

Enable port 993 IMAPs to get iPhone Mail app to work with IMAP against iRedMail (dovecot) server.

I have a iredmail server fully working with many IMAP clients (Outlook, Mac Mail, Thunderbird, etc...), however I have been battling getting it to work on IOS / iPhone Mail IMAP client.

After hours of toiling and googling, I found the solution (or issue). The secret is to enable port 993 (IMAP SSL / IMAPs) protocol in my firewall NAT rules. Meaning I had to port forward port 993 also for IMAPs. I guess this is because the iPhone does not support IMAP SSL TLS with STARTSSL using only port 143.

I hope this clue help save time for somebody else.

How to setup Advanced DNS on NameCheap for Mandrill App

Mandrill App is the self-service part of MailChimp.

Basically it is a transactional outgoing email server.  Mandrill is very cool having these features:

1. Keeps track of all your email sents.

2. Wondering what happen to that email you just sent? Why the recipient never got it?  No more of that problem. Mandrill's log will tell you why.

3. First 12,000 emails sent are FREE, and above 12,000 emails are very reasonably priced.

Okay great... those are all great... but setting up Mandrill is a chore.  Since it is transactional email, you have to authorize Mandrill's servers to send emails on your behalf.  You have to set DKIM and SPF records as TXT records into your DNS Records.

I use NameCheap, because they are cheap and have good support.

Here is a screenshot of what my NameCheap DNS settings looks like:



Once you set those records in your DNS, you should wait about 30 minutes for the records to propagate to other DNS servers worldwide.

Then, go back to your Mandrill admin panel > Settings > Sending Domains and click on the Test DNS Settings button.

If all goes well... you should see something like this:




The tricky / key part here is setting the 'host' of the DKIM to just 'mandrill._domainkey' instead of 'mandrill._domainkey.domain.com' as suggested by Mandrill's instructions.

Bash shell script to rotate log files in certain directory using array of files

The script below will automatically rotate log files (defined in array) inside certain directory.

Note the Logfiles array in variable $Logfiles.

To use this script simply save the script to filename (you can change this): rotate_logs.sh

Change the values for variables:

Directory

Extension

Logfiles

then make it executable using:

chmod +x rotate_logs.sh

-----------------------------

#!/bin/bash

Directory='/log';
Extension='log';
Logfiles=('file_1' 'file_2' 'file_3');

echo "Directory: ${Directory}";
echo "Extension: ${Extension}";
echo "Logfiles: ${Logfiles}";

for File in "${Logfiles[@]}"
do
cd ${Directory}
echo "Rotating: ${Directory}/${File} ... "
mv ${File}.${Extension} ${File}-`date +%Y%m%d`.${Extension}
touch ${File}.${Extension}
chmod 777 ${File}.${Extension}
done

------------------------------

Once rotate daily / nightly you should also remove old log files using these lines in your cron table:

crontab -e

----------------

35 3 * * * /cron_shell/rotate_logs.sh
40 3 * * * find /log -mtime +5 | xargs rm -f

----------------

The first cron table line '/cron_shell/rotate_logs.sh' is the rotate script I described above.

The second line removes files older than 5 days.