ufw – the 2 minute guide

apt-get install ufw

ufw allow ssh

but what do you know, i got an error

ERROR: initcaps
[Errno 2] modprobe: ERROR: could not insert 'ip6_tables': Unknown symbol in module, or unknown parameter (see dmesg)
ip6tables v1.4.21: can't initialize ip6tables table `filter': Table does not exist (do you need to insmod?)
Perhaps ip6tables or your kernel needs to be upgraded.

Well, that was not so nice, so i went into the file /etc/default/ufw and disabled IPv6, and now it works

So, before we enable it, i enabled SSH access otherwise i will be locked out

ufw allow ssh

now, enable it with

ufw enable

Now, enabled a few more ports for SIP for example

ZOIPER setup for a SIP account

Basically I need to give a friend of mine who is traveling a VOIP account of a special kind, So to make his experience as simple as possible, I took screenshots of the setup process, but generalized them enough for anyone who wants to setup a SIP account on zoiper.

Step1 : Install zoiper from the google play store, here is a link Install Zoiper , any other SIP CLIENT will do, but this one is the one i made the instructions for.

HINT: From here on, Just look at the pictures, no need to read all this text unless you need to know more things

Step 2: Open zoiper, then go to the config panel, then to accounts.

d1

Step 3: Click the “add account” to add an account to zoiper

d2

Step 4: When asked if you already have a VOIP account, Answer with YES

d3

Step 5: When asked if you want to configure manually, or select a provider, You would want to go with the manual configuration.

d4

Step 6: Now you need to set the account type, zoiper supports both SIP (Session Initiation protocol) which is more or less both a good standard and the defector standard in VOIP, this is the one we want, the other is called IAX (Inter Asterisk Exchange) which is specific to Asterisk, an open source VOIP system

d5

Step 7: Now, we need to give zoiper some settings to know where and how to connect, This data was given to you by your provider,

Account name: Any name you want, for example, the name of the provider, or how you use this account, you can call it my NY number, or TheTech, or any other name you want to use to identify this account

Host: The address of the server, this can be something like voip.example.com or example.com, any internet address whether FQDN or IP address should do.

Username: Self explanatory really
Password: Also self explanatory

d6

Exposing visitor IP to apache through varnish

In a previous post, i posted how you can put varnish on a virtual machine to cache content for your web server, But there was one small thing that we did not deal with, The IP address in the logs and that the website can see is simply that of the varnish server, not the visitor’s IP, and if you write PHP like me, I use the IP in everything, from securing logins to limiting page views to limiting comments. So, here is how we can work around this problem

First, the mission is as follows, Varnish needs to append something in the request header, that apache needs to consider the Visitor’s IP

To make apache do that, there is already a module (mod-remoteip) to do this

1- Tool to check the IP of the visitor

Create a PHP script to find out if what we are doing actually worked.

<?php
print "Your IP is: {$_SERVER['REMOTE_ADDR']} <br />\n\n";
$headers = apache_request_headers();
foreach($headers as $xheader => $xvalue)
{
print "$xheader : $xvalue <br />\n"; }
?>

and upload it to the website, when accessing this from the internet, you should see the IP as the IP of the varnish server, not your IP (Like it should)

1- Playing with cpanel

First, we must download mod_remoteip from the cpanel website (See here)

Once downloaded, we will upload it to the cpanel server at

/var/cpanel/easy/apache/custom_opt_mods/

Once done, we will now extract it as we would extract any tar.gz file

cd /var/cpanel/easy/apache/custom_opt_mods
tar -C /var/cpanel/easy/apache/custom_opt_mods -xvf custom_opt_mod-remoteip.tgz

Now, this mod should appear in easy apache when rebuilding apache, so go ahead, visit

Home »Software »EasyApache 3

and on the Exhaustive Options List you should be able to see mod_remoteip, be sure to check it.

Now, before coming to configure it, We need to inform Varnish to send us those headers. So add this at the very beginning of the Varnish sub vcl_recv section

NOTE: It seems that for the latest varnish (VCL 4), you no longer need this, if you add this, you will get the header as ( X-Forwarded-For : xxx.105.60.194, xxx.105.60.194) meaning the same IP twice

if (req.restarts == 0) {
  if (req.http.X-Forwarded-For) {
    set req.http.X-Forwarded-For = req.http.X-Forwarded-For + ", " + client.ip;
  } else {
    set req.http.X-Forwarded-For = client.ip;
  }
}

Now, we need to tell apache, what the extra header’s name is (X-Forwarded-For) and what servers this header should be honored for (the varnish server IPs, currently displaying in the script we wrote right after Your IP is:) So start by editing

/usr/local/apache/conf/includes/pre_virtualhost_global.conf

And add this, the IP here is the varnish server IP

<IfModule mod_remoteip.c>
   RemoteIPHeader X-Forwarded-For
   RemoteIPInternalProxy xxx.172.13.208
</IfModule>

Or, Probably the more suitable

/usr/local/apache/conf/includes/pre_virtualhost_global.conf

And add this, the IP here is the varnish server IP

<IfModule mod_remoteip.c>
   RemoteIPHeader X-Forwarded-For
   RemoteIPTrustedProxy xxx.172.13.0/24
   RemoteIPTrustedProxy xxx.172.14.0/24
   RemoteIPTrustedProxy xxx.172.19.0/24
</IfModule>

Now, visit Home >> Restart Services on your cpanel server, and restart apache

There you have it, refresh that PHP script, and your IP address should appear.

Now, the apache logs will still log the Varnish server IP, to fix that, you need to modify the log section in your apache config, changing %h with %a, like so

#LogFormat "%h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" combined
LogFormat "%a %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" combined

restoring lost tabs in firefox

Every once in a while (often), something happens and the “Restore session” option in firefox disappears (right now it is june 2016), usually this happens after a crash where i try to re open firefox early or when computer hangs then i do something stupid, if you just opened firefox, keep it open, then go to C:\Users\techg\AppData\Roaming\Mozilla\Firefox\Profiles\8xve5flx.default (Or whatever your profile folder is named), and WITH YOUR FIREFOX STILL OPEN, copy the file sessionstore.js (back it up), Now close firefox, your original might have reset to a small file size as soon as you close firefox, Now, the tabs are all stored in sessionstore.js.bak (or whatever you called the copy), so delete the one you have, and copy this file back in it’s place.

With that done, it is editing time

The bad copy starts like this

{"version":["sessionrestore",1],"windows":[{"tabs":[{"entries":[{"url":"about:home","title":"Mozilla Firefox Start Page","charset":"","ID":716087720,"docshellID":11510,"docIdentifier":13,"persist":true}],"lastAccessed":1465298115431,"hidden":false,"attributes":{},"userContextId":0,"index":1,"image":"chrome://branding/content/icon32.png"}],

delete some text (“version”:[“sessionrestore”,1],) to make it look like this

{"windows":[{"tabs":[{"entries":[{"url":"about:home","title":"Mozilla Firefox Start Page","charset":"","ID":716087720,"docshellID":11510,"docIdentifier":13,"persist":true}],"lastAccessed":1465298115431,"hidden":false,"attributes":{},"userContextId":0,"index":1,"image":"chrome://branding/content/icon32.png"}],

Now, open your firefox browser, and you should see the restore button come back up.

Mounting a multipart vmdk disk on Linux

There are many ways to do that, one of which is using the tools provided by vmware to combine the disks into one and then mounting it with

kpartx -av mydisk.vmdk;

Then

mount -o /dev/mapper/loop0p1 /hds/disk

While another method, which is simpler

apt-get install qemu-utils
qemu-img convert disk-s001.vmdk s01.raw
....
qemu-img convert disk-s013.vmdk s13.raw
....
qemu-img convert disk-s032.vmdk s32.raw

The above will be sparse files, so you will not have disk usage as big as the file, a “df -h” should not result in any lost of disk space beyond the data that is used by files in the image

following the above, we need to combine the RAW files like so

cat s01.raw s02.raw s03.raw s04.raw s05.raw s06.raw s07.raw s08.raw s09.raw s10.raw s11.raw s12.raw s13.raw s14.raw s15.raw s16.raw s17.raw s18.raw s19.raw s20.raw s21.raw s22.raw s23.raw s24.raw s25.raw s26.raw s27.raw s28.raw s29.raw s30.raw s31.raw s32.raw > combined.raw
losetup /dev/loop0 combined.raw
kpartx -a /dev/loop0
mount /dev/mapper/loop0p1 /hds/img1

Review of the Seagate ST8000DM002 8TB 7200rpm desktop hard drive

This is not a review in the sense that it explores the drive in every possible aspect, this is better seen as a user review.

I got this drive on 2016-04-06 (6th of april), the first thing that catches your eye about this drive is that every inch of the space a regular hard drive uses (that empty area under the disk) is used, as a consequence, there is no middle screw hole, only in the back and in the front, a bit of a problem for many computer and NAS cases that rely on that hole to fasten the drive in place.

So, formatting the system into ext4 and copying files onto it, the drive seems very fast, how fast exactly remains to be seen in the coming few hours as i can only run the test after ext4lazyinit completes and finalizes the ext4 partition. I also enabled lazy write-back and removed the journal (tune2fs -O ^has_journal /dev/sdb1)

Now, let us take a better look at some parameters that were given to us by seagate

This is not the SMR (Shingled magnetic recording) disk, this is a proper hard drive meant to run as your desktop’s hard drive, the hard drive features 6  1.33TB plates, which is very high density compared to any disk on the market.

Price per gigabyte at the time of writing on this drive is 4 cents, that is pretty good for a desktop hard drive (The archive drive costs less per GB, but is much less of a performer), the archiving drive, with the SMR needs to delete neighbouring bytes and rewrite them whenever it needs to update a certain byte, so it suffers in performance, not to mention that other things are designed with this in mind too.

Using cloud linux

Basically, CloudLinux sets limits on hosting accounts, here is what you need

1- Remove limits for a certain user
lvectl set-user techg –unlimited

2- Restore all limits to defaults
lvectl apply all
Or
lvectl delete-user techg

3- Increase speed of website to use 3 cores
lvectl set-user techg –speed=300%

Change the defaults
lvectl set default –speed=100% –pmem=2048m

Server unable to read htaccess file, denying access to be safe

I am very new to centos (Debian usually), and on my cpanel / whm server, i got this error

Forbidden

You don't have permission to access / on this server.
Server unable to read htaccess file, denying access to be safe

Additionally, a 403 Forbidden error was encountered while trying to use an ErrorDocument to handle the request.

Something seemed seriously wrong, I had already chowned all the files

chown -R techg:techg public_html

I also even deleted the htaccess file, but still, the server was reporting the error.

The solution turned out to be making the public_html directory executable

I found that out through the apache log files that read

[Sun Mar 06 02:48:10.894154 2016] [core:crit] [pid 1261] (13)Permission denied: [client 46.xxx.216.169:55886] AH00529: /home/techg/public_html/.htaccess pcfg_openfile: unable to check htaccess file, ensure it is readable and that ‘/home/techg/public_html/’ is executable

gigabit Ethernet VirtIO driver for Windows 10 64bit

By default, KVM gives your virtual machine a realtek rtl8139 Ethernet adapter, with an ancient 100Mbit/Second speed, we all need gigabit Ethernet adapter for the KVM guest.

The answer is changing the string rtl8139 with virtio in the XML file of the virtual machine, then installing the drivers

The steps i use are

Run virtual machine with the realtek adapter to download the other adapter’s driver
once the adapter is there, shutdown the virtual machine guest (Windows guest), then edit the xml of the guest, and restart libvirtd
start the KVM guest again
open with VNC, start the device manager, install the driver you downloaded.

You are good, the adapter should report the speed of 10Gbit/second (10 gigabit per second)

One annoying thing is that all windows drivers come in a big ISO file, you probably just want the driver you need.

I will add the download links in the coming few days, but you can get them right now if you like from fedora, the fedora windows guest drivers should work on any linux distribution (Debian, ubuntu, etc…)