Solving SSH “channel 3: open failed: administratively prohibited” error when tunnelling

A couple of days ago, I’ve encountered this error when I was trying to create a SSH tunnel from my office LAN to a remote server.

After looking for a solution, I found out that the remote SSH server must add “PermitTunnel yes” line in “/etc/ssh/sshd_config” file.

To do that, you need to:

sudo echo "PermitTunnel yes" >> /etc/ssh/sshd_config
service sshd restart

The second line is used to restart the ssh service in order to enable the changes.

iotop: How to monitor processes that hogs hard disk writes

iotop is a small and handy tool to monitor processes that hogs I/O resources. iotop outputs is similar to ‘top’ except it lists the hard disk read/write activity as well as swap writes.

You can use the left and write key to sort the heading according to your preference and the R key can be used to reverse the sort. The ‘O’ key is used when you only wants it to display processes that are currently utilizing the disk I/O. While the ‘P’ key can be used to display accumulated IO disk read/write for all the processes (which can be sorted with the arrow keys).

How to back up files periodically using rsnapshot and NFS in Ubuntu Linux

rsnapshot is a utility that uses rsync to synchronize files between two directories. rsnapshot makes it easier for system admin to backup crucial system data files regularly with minimal bandwidth and effort.

This guide assumes that you’ve already installed nfs-client and rsnapshot via “apt-get” utility in your Debian/Ubuntu Linux system.

The backup server is connected in the same LAN as the main computer. The backup server is mounted as NFS on the main computer, ip address of the backup server is

Step 1: Create a script to mount backup server filesystem
This is to ensure that the backup server is available at least hourly (or daily, depending on your requirements), save the file as “”

File content:

mount  /media/backup/

Step 2: Ensure the mount script is run hourly

sudo cp /etc/cron.hourly
sudo chmod a+x /etc/cron.hourly/

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