There are many monitoring tools available for monitoring local and remote Linux systems. A good example is the Cockpit. However, the installation and use of these tools is complicated, at least for novice administrators. The novice administrator may need to spend some time figuring out how to configure these tools to monitor the system. If you want to quickly and roughly monitor multiple hosts at a time in your LAN, you may need to look at the "rwho" tool. As soon as the rwho utility is installed, it will quickly monitor local and remote systems. You don't have to configure anything! All you have to do is install the "rwho" tool on the system you want to monitor.
Please do not consider rwho as a feature-rich and complete monitoring tool. This is just a simple tool that monitors only the "uptime", "load", and logged-in users of remote systems. Using the "rwho" usage program, we can find out who is logged on on which computer; a list of monitored computers that lists the uptime (the time since the last restart); how many users are logged in; and Average load over the past 1, 5, and 15 minutes. no more, no less! Moreover, it only monitors systems in the same subnet. Therefore, it is very suitable for small and home office networks.
Monitor multiple hosts in Linux
Let me explain how rwho works. Every system that uses rwho on the network broadcasts information about itself, and other computers can use the rwhod daemon to access this information. Therefore, every computer on the network must have rwho installed. In addition, rwho ports (such as port 513/UDP) must be allowed to pass through the firewall/router in order to distribute or access information from other hosts.
OK, let's install it.
I tested on the Ubuntu 16.04 LTS server and rwho is available in the default repository, so we can use the APT package manager like this one to install it.
$sudo apt-get install rwho
On RPM-based systems such as CentOS, Fedora, RHEL, use the following command to install it:
$sudo yum install rwho
If you are behind a firewall/router, make sure that you have allowed the rwhod 513 port. In addition, use the command to verify that the rwhod daemon is running:
$ sudo systemctl status rwhod
If it is not already started, run the following command to enable and start the rwhod service:
$sudo systemctl enable rwhod
$sudo systemctl start rwhod
It is time to monitor the system. Run the following command to find out who is logged on on which computer:
$rwho
Ostechni ostechnix:pts/5Mar1217:41
Root server:pts/0Mar1217:42
As you can see, there are currently two systems in my LAN. The local system user is ostechnix (Ubuntu 16.04 LTS) and the remote system user is root (CentOS 7). As you may have guessed, rwho is similar to the who command, but it monitors remote systems.
Moreover, we can use the following command to find the uptime of all running systems on the network:
$ruptime
Ostechnix up2:17,1user,load0.09,0.03,0.01
Server up1:54,1user,load0.00,0.01,0.05
Here, ruptime (similar to the uptime command) shows the total runtime of my Ubuntu (local) and CentOS (remote) systems. do you understand? Excellent! The following is a sample screenshot of my Ubuntu 16.04 LTS system:
You can find information on all other machines in the LAN in the following locations:
$ls /var/spool/rwho/
Whod.ostechnix whod.server
It's small, but it's very useful to find out who is logged on on which computer, as well as uptime and system load details.
Suggest reading:
Please note that this method has a serious flaw. Because information about each computer is broadcast over the network, everyone in the subnet can obtain this information. This is usually the case, but on the other hand, when the information about the network is distributed to unauthorized users, this may be an unnecessary side effect. Therefore, it is highly recommended to use it in a trusted and protected LAN.
For more information, look for the man man page.
$man rwho
Well, this is all. More good things are coming, so stay tuned!
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