Build NFS Server on CentOS 7

As the first step, we will install these packages on the CentOS server with yum:

yum install nfs-utils

Now create the directory that will be shared by NFS:

mkdir /var/nfsshare

Change the permissions of the folder as follows:

chmod -R 755 /var/nfsshare
chown nfsnobody:nfsnobody /var/nfsshare

We use /var/nfsshare as shared folder, if we use another drive such as the /home directory, then the permission chnges will cause a massive permissions problem and ruin the whole hierarchy. So in case we want to share the /home directory then permissions must not be changed. Next, we need to start the services and enable them to be started at boot time.  Continue reading “Build NFS Server on CentOS 7” »


Install webmin in Centos 7

Step 1 — Installing Webmin

First, we need to add the Webmin repository so that we can easily install and update Webmin using our package manager. We do this by adding a new file called /etc/yum.repos.d/webmin.repo that contains information about the new repository.

Create and open this new file using your text editor:

sudo vi /etc/yum.repos.d/webmin.repo

Then add these lines to the file to define the new repository:

name=Webmin Distribution Neutral

Save the file and exit the editor. Next, add the Webmin author’s PGP key so that your system will trust the new repository: Continue reading “Install webmin in Centos 7” »


Allow large attachment (greater than 10MB) in ISPConfig postfix MTA

Just a small hack, but worked good on my ISPConfig 3 setup. Add the following:

nano /etc/postfix/

mailbox_size_limit = 104857600

Save and restart postfix service.

According to official postfix documentation:
message_size_limit (default: 10240000) The maximal size in bytes of a message, including envelope information. Note: be careful when making changes. Excessively small values will result in the loss of non-delivery notifications, when a bounce message size exceeds the local or remote MTA’s message size limit. Continue reading “Allow large attachment (greater than 10MB) in ISPConfig postfix MTA” »


Test your DNS using Dig, Nmap, Tcpdump

For DNS resolution to succeed to, the DNS server at will need to accept TCP and UDP traffic over port 53 from our server. A port scanner such as the nmap tool can be used to confirm if the DNS server is available on port 53 as shown below.

Note: To install nmap run ‘yum install nmap -y’.

[root@centos ~]# nmap -sU -p 53
Starting Nmap 6.40 ( ) at 2015-08-26 15:22 AEST
Nmap scan report for
Host is up (0.00091s latency).
53/udp open|filtered domain
MAC Address: 02:00:79:55:00:0D (Unknown)
Nmap done: 1 IP address (1 host up) scanned in 0.29 seconds

[root@centos ~]# nmap -sT -p 53
Starting Nmap 6.40 ( ) at 2015-08-26 15:22 AEST
Nmap scan report for
Host is up (0.00099s latency).
53/tcp open domain
MAC Address: 02:00:79:55:00:0D (Unknown)
Nmap done: 1 IP address (1 host up) scanned in 0.07 seconds

Continue reading “Test your DNS using Dig, Nmap, Tcpdump” »


Webmin installation on Centos

Installing the RPM

If you are using the RPM version of Webmin, first download the file from the downloads page, or run the command :


then install optional dependencies with :

yum -y install perl perl-Net-SSLeay openssl perl-IO-Tty perl-Encode-Detect

and then run the command :

rpm -U webmin-1.870-1.noarch.rpm

Continue reading “Webmin installation on Centos” »


CentOS 5 Repository fix using

It’s a bit silly process, googled hours but found not solid way to update my old 32bit centos 5 linux box. So came up with a solution of my own. It might work for you, but no guarantee!

Remove all .repo inside /etc/yum.conf.d/ directory

Create a new repo file inside /etc/yum.conf.d/ 

nano /etc/yum.conf.d/CentOS-Vault.repo 

Update with the following section: Continue reading “CentOS 5 Repository fix using” »


Add Google Calendar to Thunderbird Mail Client

There are two plugins that must be installed:

Install both of these plugins, from within Thunderbird (Menu button | Plugins | See all and then search for Lightning and then Provider for Google. Click Add to Thunderbird and then, when prompted, restart the app).

Once these have been installed, and Thunderbird restarted, you’re ready to configure.

Adding a Google Calendar
Open up the Lightning calendar tab (click on the Lightning icon in the top right corner of the Thunderbird window). Right-click a blank spot in the Calendar pane (left side of the window) and click New Calendar. In the resulting window (Figure A), click On the Network and then click Next.

Created with GIMP

Figure A

Creating a new calendar in Lightning.
In the Locate your calendar window (Figure B), select Google Calendar, and click Next. Continue reading “Add Google Calendar to Thunderbird Mail Client” »


Convert .ova and import it on Proxmox KVM virtualization

Let’s start uploading the exported ova file to the proxmox server. Extract the OVA file:

tar -xvf *.ova

This should output a couple of files from the OVA container, it should include an OVF file, which is the VM Defenition file, and a VMDK file, which is the actual hard disk image. Again, this may take a while.

Convert the vmdk to a Proxmox compatible qcow2 file:

qemu-img convert -f vmdk myvirtual-disk1.vmdk  -O qcow2 qcowdisk.qcow2

We now need to get the image into a VM with some hardware so that we can begin to use it. This is where things get tricky – the OVF file is not compatible with Proxmox and needs to be manually understood. The principle here is we are going to use the Proxmox web GUI to create a VM and replace the empty disk image which is created with our recently converted qcow2 image.

You can use vi to open the OVF file and understand some of the basic settings which are required for the VM. Open the OVF file and look for the following XML tags:

  • OperatingSystemSection
  • VirtualHardwareSection
  • Network
  • StorageControllers

Continue reading “Convert .ova and import it on Proxmox KVM virtualization” »


Fix on connecting to NFS server from Proxmox Centos 7 Container

I hope you already know how to allow NFS from proxmox host server. if not, you may read my earlier post:

NFS fix on LXC Host Server

I was actually receiving a error like below:

# mount -t nfsd nfsd /proc/fs/nfsd
mount: nfsd is write-protected, mounting read-only
mount: cannot mount nfsd read-only

My proxmox edition was 5.0-30 and my CentOS was 7.

However, this is a bit different rather looking the other one as mentioned above. I was experiencing connecting my Centos 7 LXC container to a NFS server in the network. The regular tweak didn’t work. So, had to spend a while googling the solution. Found the correct one on a forum thread. But eventually it worked. For this you need to edit the file

nano /etc/pve/lxc/<your container ID>.conf

Add the below line in the conf file:

lxc.aa_profile: unconfined

Reboot the container. And now try to connect the NFS server. It should work.