Here is a simple script with configuration file to generate a self-generated SSL certificate (cert/key pair).

First define a config file openssl.cnf containing the certificate informations:

Then, create the bash script makessl.sh and configure your own parameters (directories, cert filename and validity duration):

Now, execute the bash script:

Let’s check your freshly created certificate and double check the information:

You can get standard information about the certificate directly by opening a connection to a website:

Answer will be like:

But this is not giving you some interesting information like the expiration date for example! To work around that, you can simply redirect the output (certificate) to openssl and ask for some specific information:

This time, output will be:

You already probably noticed that if you want to update the ownership of a symbolic link on any UNIX system, a simple chown won’t do the job.

Indeed, let’s suppose you have this:

If you’re doing a simple chown:

You can see that it changes the ownership on the target file and not on the symbolic link:

If you want to update the symbolic link, you need to use the -h or –no-dereference option to apply the changes on the symbolic link and not on the target:

Then, you can see that it’s now updated:

There is no easy way to remove a list of mails in queue with a same sender or domain in Postfix. But you can use some standard commands to get this working.

First check the list of mails you want to remove with something like

You’re getting the list of mails that you will remove with the sender

And now you can remove those mails from the queue by using postsuper -d

You will see the mails being removed

It is possible to modify a partition size on EXT filesystem thanks to some few commands.

We will take here a simple example:

• We have a /dev/sda5 partition mounted on /home
• Its size is currently 150G and we want to reduce it to 100G

Let’s check the current config (mounting point and size):

We need to first unmount the partition:

If you can’t unmount it, double check what process is using it with the lsof command:

Then proceed with a check with e2fsck command and resize the partition with resize2fs by defining the new size (M for Megabytes, G for Gigabytes, and so on…)

Mount your partition back to your system:

And check again your partition sizes :

We can see that the partition /home has now a size of 100G as expected!