Jan 24 2018

How to boot from a USB Mass Storage Device on a Raspberry Pi 3

This tutorial explains how to boot your Raspberry Pi 3 from a USB mass storage device such as a flash drive or USB hard disk. Be warned that this feature is experimental and does not work with all USB mass storage devices. See this blog post from Gordon Hollingworth for an explanation of why some USB mass storage devices don’t work, as well as some background information.

Source: How to boot from a USB Mass Storage Device on a Raspberry Pi 3 – Raspberry Pi Documentation
Related article: How to Boot Up Raspberry Pi 3 from External Hard Disk – Make Tech Easier

Jan 02 2018

Why your game console or home VoIP PBX won’t work with OPNsense or pfSense, and how to fix it

If you have been using a standard router and decide to upgrade to OPNsense or pfSense (I personally recommend OPNsense, solely because of the heavy-handed moderation in the pfSense user forum, where a user can apparently get banned for life for even a small inadvertent infraction), you may find that making a game console or a VoIP PBX work isn’t as simple as just forwarding some ports. The other thing you have to do is shown in this video:

Although the video specifically mentions the PS4 and XBOX, the advice shown is equally valid for other types of game consoles and for home PBX servers. Note the section starting at 3:20 in the video, where the “Static Port” checkbox is checked – this is the key to making it work!

The OPNsense user interface will look a bit different than the one in pfSense but the principle is the same; you still need to make sure the “Static Port” checkbox is checked. And in either case, you may still need to do port forwarding, the same as you did on your previous router, but generally speaking port forwarding alone will not work until the additional configuration shown in the video is applied. Here’s an example of setting up a static port rule in OPNsense (note that the source address field refers to a previously-set alias for the IP address of the Asterisk PBX):

VoIP PBX users, there is one other thing you may need to do, at least in OPNsense, particularly if you find that you have a non-local extension that is unable to connect to your PBX. If you are using a Dynamic DNS address, make sure you go to System: Settings: Administration and put that dynamic DNS address in the “Alternate Hostnames” field.

Dec 22 2017

A Bash script to rewrite the "static" IP address in the FreePBX Asterisk SIP Settings when it is changed by your ISP

This post is going to be a bit long because I first need to explain the “why” behind this script, then the script itself and how to test it after installation. Please note that the screenshots below are from earlier versions of FreePBX, and you probably will be using a more modern GUI interface, but the settings shown should still appear.

If you are using a recent version of Asterisk and FreePBX you may be using the Asterisk SIP Settings module (under the “Settings” tab) to automatically set various SIP parameters.  This module is a great help to those who don’t know what they are doing, but there is a trap for the unwary (and in this case it’s NOT the fault of FreePBX – it’s a longstanding bug in Asterisk that’s the problem).

At the top of the Asterisk SIP Settings configuration page, in the NAT Settings section, there are two options that can be set.  The first is NAT and there are four possible choices:

  • yes = Always ignore info and assume NAT
  • no = Use NAT mode only according to RFC3581
  • never = Never attempt NAT mode or RFC3581
  • route = Assume NAT, don’t send rport

In theory, if you have a fixed IP address AND your Asterisk server is not behind an external router that does NAT translation, you should use “no” (and most of the rest of this article will not be relevant to you).  This article is intended more for home and SOHO users that both have their Asterisk server behind a hardware router of some kind, and that get their broadband service from a company that occasionally changes their IP address without warning.  For such users, the preferred setting is “yes”.  I’m not enough of a networking guru to tell you under what circumstances one of the other settings might be appropriate (if you understand this stuff, feel free to leave a comment and enlighten us).

FreePBX: Asterisk SIP Settings page, Chan SIP Settings tab, NAT Settings (Public IP Option)

It’s the next set of settings that can get us into trouble.  This is the IP Configuration and there are three possible choices:

  • Public IP
  • Static IP
  • Dynamic IP

If your IP address never changes AND you aren’t behind a hardware firewall then you can usually just set this to “Public IP” and let it go at that.  You will not be asked to fill in any other values.  But most users that are not in that situation will pick one of the other two choices, and this is where the problem arises.  Conventional wisdom has it that if your ISP ever changes your IP address without advance warning (which is the case for most cable broadband and DSL users), you should use the Dynamic IP setting.  In this case there is an auto-configure button that will fill out the fields for you, although you may need to fill in the Dynamic Host field yourself.  This is the “External FQDN as seen on the WAN side of the router and updated dynamically, e.g. mydomain.dyndns.com” (as explained if you mouse over the words “Dynamic Host”).  You can use a DynDNS address (or an address from a similar service) or an address you have purchased.  But the problem is that for some users, THIS METHOD SIMPLY DOES NOT WORK.

FreePBX: Asterisk SIP Settings page, Chan SIP Settings tab, NAT Settings (Dynamic IP Option)

If you try to use Dynamic IP and it won’t work for you, what happens is you will get all sorts of weird errors.  You may get one way audio, some calls may disconnect for no apparent reason after about five seconds, and you will see other weird errors in your CLI.  If you change this setting to “Static IP” and click the auto-configure button and then submit the changes, the problems magically go away – UNTIL your ISP changes your IP address, at which point you suddenly have no connectivity to the outside world.  If you ask for help, everybody and their brother will tell you to use the Dynamic IP setting, and the minute you try that you’ll get all the weird errors again.

FreePBX: Asterisk SIP Settings page, Chan SIP Settings tab, NAT Settings (Static IP Option)

FreePBX: Asterisk SIP Settings page, General SIP Settings tab, NAT Settings, showing static external IP address

So if that’s your situation, you need set a Static IP address as shown in the above two screenshots (this used to be all on one page, but now it’s under two separate tabs in the new interface), and you need this Bash script.  Coupled with a cron job, it goes out and checks your IP address every five minutes and if it notices it has changed, it changes it in the MySQL database (same as if you entered it into the External IP text box on the Asterisk SIP Settings configuration page) and then reloads Asterisk.  Therefore, you can use the Static IP method and it hopefully it will work reliably.  If and when your IP address changes, you should only be down for about five to ten minutes at most (hopefully your broadband provider usually does such changes in the middle of the night!).

A word to the wise, do NOT enter anything into the “Override External IP” field under the “Chan SIP Settings” tab unless you are certain that you know what you are doing, or you may have “no audio” issues. You should only put your external IP address in the “External Address” field under the “General SIP Settings” tab.


You will need to use a Dynamic DNS service to keep track of your IP address if you want external extensions to be able to find your server on the Internet.  It’s not required for this script to work, though, so I won’t say any more about that except to note that if you use a recent vintage hardware router, it probably has DDNS support built in.

The Script:

Note that WordPress MAY change apostrophes and quotes into “prettified” versions, and if it does that will totally mess up Bash.  I’m going to put this in a preformatted text block so hopefully WordPress won’t change anything (it doesn’t appear that it has), but you never know.  Also, don’t confuse backticks (`) with apostrophes (‘) – backticks are used around the word `key` in the script below.

This script was written for use with FreePBX 14; there are some minor changes that need to be made for earlier versions (for example, you may need to use kvstore in place of kvstore_Sipsettings where it appears in the script). If you are running an earlier version you can either use the Perl version of this script from A Perl script to rewrite the "static" IP address in the FreePBX Asterisk SIP Settings when it is changed by your ISP, or at least see that article to see an explanation of the changes.

There are long lines in this script that overflow the allotted display area, so you will probably want to copy and paste the entire script (except for the final three commented out lines if you don’t need it to update a Dynamic DNS; see below) into a text editor such as nano. Make sure you do copy the last line, which contains only “fi”, or it won’t work.

# This program gets the current IP address (as assigned by the ISP) from
# OpenDNS and modifies the FreePBX Asterisk SIP settings if the external IP
# address has changed. Invoke it as cron job that runs every 5 minutes.
check=$(dig +short myip.opendns.com @resolver1.opendns.com) || { echo "Problem getting current IP address"; exit 1; }
if [[ ! $check =~ ^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
  echo "Invalid IP address"; exit 1;
readip=$(mysql asterisk -u $user -p$pass -se 'SELECT val FROM kvstore_Sipsettings where `key` = "externip"') || { echo "Can't read externip from MySQL asterisk database"; exit 1; }
if [ "$check" != "$readip" ]; then
# IP address has changed
# Send email
# echo "This is an automated message - please do not reply. It appears that our external IP address has been changed to $check" | mail -s "External IP address may have been changed" you@someaddress.com
# Save new IP address to Asterisk SIP settings
mysql_response=$(mysql asterisk -u $user -p$pass -se 'update kvstore_Sipsettings set val='\"$check\"' where `key`="externip" ')
# Reload Asterisk
/var/lib/asterisk/bin/module_admin reload
# Update freedns
# date > /tmp/freedns_uodate.log
# /bin/sleep 21 ; /usr/bin/wget --no-check-certificate -O - https://freedns.afraid.org/dynamic/update.php?uniqueupdatestring== >> /tmp/freedns_update.log 2>&1 &

NOTES on the above script, including THINGS YOU MUST CHANGE:

Note the two bolded variables user and pw. These must be changed to the correct values for YOUR system. You will usually find these in one of two places. You can look in /etc/amportal.conf and look for the variables AMPDBUSER and AMPDBPASS — these will usually be near the bottom of the file in newer installs, in a “— CATEGORY: Bootstrapped or Legacy Settings —” section, but they can be anywhere in the file.

Another place they may be found is in the file /etc/freepbx.conf — in that file, look for lines similar to:

$amp_conf[‘AMPDBUSER’] = ‘freepbxuser’;
$amp_conf[‘AMPDBPASS’] = ‘password’;

Those will give you the values to insert into the user and pw variables in the script. YOU MUST INSERT THE CORRECT VALUES OR THE SCRIPT WILL NOT WORK! By the way, if you have both of the above-mentioned files, make sure that the AMPDBUSER and AMPDBPASS variables are set to the same respective values in both files, otherwise your CDR Reports page may not work.

If you want an e-mail notification when your IP address has changed (which is recommended), uncomment the next line under “# Send email” and modify the email address appropriately (make sure you use one or more valid e-mail addresses; you use a comma to separate addresses if you use more than one). Note this will only work if your system is already configured to send outgoing email.

You can also use this script to update a Dynamic DNS; if you use freedns.afraid.org as your Dynamic DNS then you could uncomment the two lines under “# Update freedns” and change the update URL to the unique one for your account. Don’t uncomment those lines unless and until you have the correct update URL for YOUR freedns account!. If you don’t want this script to update a Dymanic DNS account (as might be the case if you have your router set to perform this function) then you can just omit the final three commented out lines of the script – make sure you DO include the “fi” at the end of the script, though!

Note that in two places in the script (the lines that access MySQL) the word `key` appears within backtick quotes. If you leave out the backticks, or change them to something else such as apostrophes, IT WILL NOT WORK. Backticks and apostrophes are NOT the same character!

Save your script to either the /root directory or the /var/lib/asterisk/agi-bin directory, or to another location of your choosing. I named it checkip.sh. You must make the script executable, for example:

chmod u+rx /var/lib/asterisk/agi-bin/checkip.sh

Of course you will specify the correct filename and directory. Now it’s time to test the script. From the Linux command prompt, navigate to the directory where you stored the script:

cd /var/lib/asterisk/agi-bin

Now run the script from the command prompt:


Hopefully you won’t see any error messages. Remember it’s going out to do a query to get your external IP address, so don’t get concerned if it takes a second or two. If you had an incorrect address stored in your FreePBX Asterisk SIP Settings configuration, it will take longer because it will reload the FreePBX configuration. The script has a check to make sure it only stores a real IP address (and not something invalid like an error message) in the database, so if it appears to not be working, make sure the underlying call to the dig command is returning a valid IP address. By the way, that IP address check is rather rudimentary, and really only checks that the address only contains four sets of numbers separated by three dots, so if the dig command were to somehow return a totally bogus, but valid looking IP address, it might not get caught, however that’s highly unlikely to happen. That said, if you know of a better way to validate an IP address (or for that matter, see a better way to do anything in this script), please leave a comment!

If you do get an error, check that you copied the entire script correctly (including the ending “fi” statement), and that you made all the necessary changes as indicated above. Also check to make sure that you made the script executable.

Setting up a cron job

Once it runs without errors, you will want to create a cron job so it runs automatically every five minutes. Do NOT run it more often than that, or the lookup service may ban your IP address, and you don’t want that to happen, and besides, it’s not polite to hog the resources of someone else’s server! And if you are running it on multiple servers at the same IP address, then adjust the polling speed so that the total polling from all servers doesn’t exceed once every five minutes. An occasional additional test is probably not an issue, but if you try to poll every minute you just might get banned!

The usual way to add a cron job is to run this command:

crontab -e

(If you’re not currently running as root use sudo crontab -e instead)

This will open a text editor showing your current cron jobs. Just add a new line to the bottom of the file with your new cron job. To run the script every five minutes, you could use something like this:

*/5 * * * * /var/lib/asterisk/agi-bin/checkip.sh

Or to be more specific as to when the script runs (this will run it exactly on the hour, at five minutes after the hour, at ten minutes after the hour, and so on):

0,5,10,15,20,25,30,35,40,45,50,55 * * * * /var/lib/asterisk/agi-bin/checkip.pl

Just save the changed file when you are finished. The alternate method is to use Webmin’s System | Scheduled Cron Jobs module to set up your cron job.

Final testing:

The easiest way to test to make sure this is all working is to wait until a time that there are no active calls on the system, then go to the Asterisk SIP Settings configuration page and change the External IP address to something invalid (just change the last digit of the current address and Submit Changes, then do the usual configuration reload). On the next five minute interval, the script should detect that the external IP address doesn’t match the one stored in the database, and it will write the correct value to the database and reload the FreePBX configuration. If you watch the Asterisk CLI during this time, you should actually see the reload take place. After that, if you go back to the Asterisk SIP Settings configuration page, the correct IP address should be there. To be extra safe, you should also view the contents of the file /etc/asterisk/sip_general_additional.conf and make sure that the externip= line shows the correct IP address.

Now you don’t have to worry about frantic calls from users at inopportune times because your ISP changed your IP address and none of the phones are working, and you also won’t have any of the problems associated with the Dynamic IP method!

NOTE: Again, this script should be considered experimental, and as usual, there are no warranties — we’re experimenters here, and sometimes we don’t catch all the bugs, especially on the first go around! However, I would assume that anyone who is running a “professional” installation would pay their ISP for a true static IP address (one that never changes), and therefore wouldn’t need this type of script.

Dec 21 2017

Google Chrome Asks Password to Unlock Login Keyring

For Ubuntu users who get problem that Google chrome asks for password to unlock the login keyring on every startup, as the picture shown below, a workaround is to set the default password store from gnome (or kwallet) keyring to chrome’s built-in.Enter password to unlock your login keyring

Source: Google Chrome Asks Password to Unlock Login Keyring – Tips on Ubuntu

Dec 18 2017

How to Create a .Desktop File For Your Application in Linux

Some applications don’t show up in your Application menu. This article shows you how to create a .desktop file in Linux so you can launch your favorite apps from the Application menu.

Source: How to Create a .Desktop File For Your Application in Linux – Make Tech Easier

Dec 17 2017

Rsync Over Ssh On Different Port In Linux

Rsync and SSH tools on different Linux port to copy local as well as remote files. Backup important data to secure place with Rsync and SSH in Linux.

Source: Rsync Over Ssh On Different Port In Linux (LinOxide)

Dec 16 2017

How to Block Adblock Detection on Any Website

Advertisers are taking steps to bypass adblockers on browsers. If you are an adblock user, here is how you can block adblock detection on websites.

Source: How to Block Adblock Detection on Any Website – Make Tech Easier

Dec 10 2017

12 Different Options of Rsync Command in Linux With Examples

This article shows different practical usage of rsync command and its options in linux with detailed examples

Source: 12 Different Options of Rsync Command in Linux With Examples (LinOxide)

Dec 09 2017

How to Downgrade Packages on Ubuntu (and possibly other Debian-based distributions?)

This is an older article but I believe the information is still valid. The technique shown may also work on other Debian-based distributions, such as Linux Mint and the various Ubuntu derivatives.

Ubuntu’s Update Manager keeps your packages at the latest version, but occasionally a new package version may not work properly. You can downgrade an installed package and lock it at a specific version to prevent it from being updated.

Source: How to Downgrade Packages on Ubuntu (HowToGeek)

Dec 02 2017

What Is SED and How Do You Use It?

Sed is a powerful command akin to the find and replace feature in most text editors. Find out what sed is and how you can use it to improve your efficiency.

Source: What Is SED and How Do You Use It? – Make Tech Easier

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