Some kinds of software require only one format of SSL certificates. This is the way how you can convert certificates between two popular formats (PEM and DER).

Use ‘openssl’:

openssl x509 -inform DER -in der-cert.crt -outform PEM -out pem-cert.pem

And vice versa:

openssl x509 -inform PEM -in pem-cert.pem -outform DER -out der-cert.crt


This short article describe how to reset lost root password on Linux system. IMPORTANT: This method require physical access to the machine.

On GRUB screen select normal boot option:

1Press ‘e’ to edit selected option. You will see short GRUB code.


Search for the line starting with “linux /boot/vmlinuz…” or similar depending of Linux distribution. This is the place where kernel and rootfs is selected. Change ‘ro’ option to ‘rw’ and add: Continue Reading

Sometimes happens that establishing of SSH (or other service) connection takes a really long time. This is often caused by failed reverse DNS lookups.

That situation can occur because of network problems or can be intentional action performed by system administrator.

How can you handle with it? Simply add this line to your sshd_config file.

UseDNS no

Now SSH connection should be established significantly faster.