Extending Virtual Disk in a Linux Virtual Machine Using LVM

To increase a disk size in a virtual machine with Linux operating system configured with LVM, below are the steps (these steps were tested using virtualbox):

1. Power off the virtual machine

2. Increase the virtual disk size in the virtual machine using the virtual machine manager

3. Restart the virtual machine

4. Even though the virtual disk has been increased in size, but LVM is not aware of the change. To make LVM aware of the change, run pvresize command

$ sudo pvresize <pv name>

You can get the physical volume (PV) name by running "pvs" command

$ sudo pvs

5. Once the physical volume (PV) has been resized, run "vgs" to see the new volume group (VG) size

$ sudo vgs

6. Resize logical volume (LV) to make the new size available for us to use. Use below command to resize LV to use 100% of the free space available in VG

$ sudo lvextend -l +100%FREE <LV path>

You can get the LV path by running lvdisplay

$ sudo lvdisplay | grep Path

7. Now the partition is aware of the size change, but not the filesystem. Check the filesystem type and mountpoint using below command

$ df -Th

8. Depending on the filesystem type, extend your filesystem to suit the new partition size. 

For xfs:

$ sudo xfs_growfs <mountpoint>

and for ext4:

$ sudo resize2fs <mountpoint>

9. Verify that your filesystem is now using the new size

$ df -Th

Splitting video using linux command line

To easily split (or cut some part) of video using command line, a tool called ffmpeg can be used.

Why use command line? Lighter on resource. Video editing is a high resource activity, and by using command line, we can reduce the resource used on our machine while doing video splitting, especially if we are using low resources machine. 

To install ffmpeg, on an debian based machine, just run below command

$ sudo apt -y install ffmpeg

To do the splitting, just use below command

$ ffmpeg -i mymovie.mp4 -ss 00:01:00 -t 00:00:30 myeditedmovie.mp4

where

-i is for which video to edit

-ss is for where in the video that you want to start

-t is for the duration of the output video

So in the above example, you will get an output called myeditedmovie.mp4, which start from the first minute of the original video, and will last 30 seconds.

Testing SSL Certs Using Apache on Docker

Sometimes we have a need to test our SSL, before we deploy it to production. If we have a development or staging environment, then we can test it there. But if we do not have that, we can always rely on trusty old docker to test the ssl in our own machine. Please follow along to learn how to do it.

Pre-requisite:

- have docker installed 

1. Put our ssl cert, intermediate cert (if we have one) and key into our current directory. Rename them as server.crt, server.key and server-ca.crt

2. Prepare a configuration file like below inside our current directory, and save it as https.conf

Listen 443

<VirtualHost _default_:443>

  DocumentRoot "/usr/local/apache2/htdocs"

  ServerName linuxwave.info

  ServerAdmin me@linuxwave.info

  ErrorLog /proc/self/fd/2

  TransferLog /proc/self/fd/1

  SSLEngine on

  SSLCertificateFile "/ssl/server.crt"

  SSLCertificateKeyFile "/ssl/server.key"

  SSLCertificateChainFile "/ssl/server-ca.crt"

</VirtualHost>

3. Run a container based on the httpd image from dockerhub, and mount the current folder with our ssl key and certs into /ssl in the container

docker run -dit --name apache -v ${PWD}:/ssl httpd

4. Copy /usr/local/apache2/conf into /ssl, so that we can edit it inside our host machine

docker exec -it apache cp /usr/local/apache2/conf/httpd.conf /ssl

5. Enable ssl in apache config by adding these lines into httpd.conf. We can just edit the file in our host machine, since text editor is not installed by default inside the apache image. The first 2 lines are to enable ssl support for apache, and the last line is for apache to include any files that end with .conf into its configuration

LoadModule ssl_module modules/mod_ssl.so

LoadModule socache_shmcb_module modules/mod_socache_shmcb.so

Include conf/extra/https.conf

6. Copy the edited httpd.conf file back into its original location

docker exec -it apache cp /ssl/httpd/conf /usr/local/apache2/conf

7. Create a symlink from /ssl/https.conf into /usr/local/apache2/conf/extra/

docker exec -it apache ln -s /ssl/https.conf /usr/local/apache2/conf/extra

8. Test the configuration file

docker exec -it apache httpd -t

9. If no error was found from the above command, restart the container

docker restart apache

10. Open a new terminal, and get the ip address of the container

docker inspect apache | grep IPAddress

11. Put the ip address and your hostname inside your machine's /etc/hosts

echo "172.17.0.2 linuxwave.info" | sudo tee -a /etc/hosts 

12. Try to access the above domain using a web browser, and check the ssl cert information

13. If the ssl certs are working fine inside docker, you can be sure that it will work just fine in your production server

Connect to Fortinet VPN using Openfortivpn

Fortivpn does offer 2 clients for linux, one is for redhat family and the other installer is for ubuntu/debian family. You can download the installers from here. 

But for those who wanted to used opensource vpn client to connect to Fortinet VPN, we can use openfortivpn. Please follow below steps to connect using openfortivpn

1. Install openfortivpn

$ sudo apt install openfortivpn

2. We can connect just by using openfortivpn with some options, like below

$ sudo openfortivpn myvpnserver.local:10443 -u vpnuser -p mypass 

where:

-u : please provide username

-p : please provide password

myvpnserver.local:10443 : please provide vpn server address and port

3. We can also use a configuration file with content like below

host = myvpnserver.local

port = 10443 

username = vpnuser

password = mypass

save the above file as myvpn.config and connect using below command so that openfortivpn can use the configuration inside the file to connect to vpn

$ sudo openfortivpn -c myvpn.config 

4. We can get all the configuration for the file, by referring to the manual page of openfortivpn. We can access the manual by running below command

$ man openfortivpn

Another Way To Check UDP Port to a Linux Server

In a previous post, I have shared a way to check for udp port allowance to a linux server using netcat and ngrep.

I have found out an even easier way to accomplish this, just by using netcat, without the need to install additional software like ngrep.

To do this, first we need to setup a netcat to listen to the udp port, in the target machine. For example, we wanted to test udp port 10000 allowance, just run below command on the target machine

$ nc -klu 10000

The command will hang there, waiting for a connection to be sent to it.

In the client machine, just use netcat to send some text over to the target machine, like below (assuming the ip address of the target machine is 10.10.10.10)

$ echo "testing udp" | nc -u 10.10.10.10.10000

If the udp port is not blocked, we will see the "testing udp" text printed on the terminal in the target machine, where we listen for 10000 udp, like example below