Telnet Linux

Telnet Linux

06/25/2018

Telnet is the traditional and very old protocol (similar to SSH) for remote console connections over TCP/IP. The telnet communication software is a user text mode interface to the TELNET protocol. Default protocol is TCP and port is 23. Telnet protocol was created in 1969 used to remote of systems over Network via text mode.

The telnet command is used for interactive text communication with another server or client using this protocol. Telnet is two sides: the server-side service and client program.

telnet-linux

How to install telnet server

Ubuntu

# apt-get install telnetd

CentOS/RedHat

# yum install telnet-server telnet

Red Hat enterprise Linux

# up2date telnet-server telnet

Activate the Telnet server on Linux:

# systemctl telnetd start
# systemctl telnetd enable

How to use telnet client

open terminal and type:

# telnet IP_ADDRESS 23

With telnet you can connect to a remote Linux computer or run programs remotely and general plan of administration.

If required you could change access permissions and allow root user login to telnet server. To do this you have to modify the /etc/security file.

Telnet Commands: USER, PASS, LIST, RETR, and DELE.

insmod

insmod module in the Linux

June 25, 2018

insmod is a simple and fast program to insert the modules inside the Linux kernel.

insmod is very close to program modprobe, insmod does not read its modules from a set location and automatically insert them and take care of any dependencies.
The surrounding variable MODULECONF can also be used to choose the contrasting configuration file from /default/etc/modules.conf

insmod

insmod examples:

# insmod ppp or # insmod /var/src/sound_driver.ko

Once you’ve inserted the module, use lsmod command to check that the module has been inserted strongly as you could see below:

# lsmod | grep ppp

What’s the difference between insmod and modprobe?

modprobe reads the modules from /lib/modules/$(uname -r)/modules.dep.bin

insmod on the other hand accepts pathway to files. The module does not have to settle in /lib/modules/$(uname -r), but dependencies are not automatically uploaded. This is the lower program used by modprobe to load modules.

When you use insmod to insert the module, I may get there error “Invalid module format”.
In this scenario it may be:

– Your module was built for an earlier kernel
– Install the latest kernel version and reboot

NVMe temperature

How to check NVMe temp in Linux?

June 25, 2018

Do you use Linux machines in Real-time task? If yes, it is presumably a excellent plan to regularly inspect the health of the NVMe drives used on Linux computers. Here is how you could do this.

The newer super fast NVMe drives provide absolutely amazing performance, but one big problem with these dries is that they are going to throttle if the drivers get very hot temperature. To prevent the issue of overheating and throttling NVMe drives we recommend to check temperature on a daily basis. NVMe driver is natively included in modern Linux systems. With nvme-cli package you can do it and many other interesting tasks with NVMe drives.

nvme-cli-linux

Using nvme-cli, you could check temperature from the drive with this command:

nvme smart-log /dev/nvme0 or nvme smart-log /dev/nvme0 | grep “temperature”

Let’s run a short test on the drives and check list of drives:

sudo nvme list

How to install nvme-cli?

To install nvme-cli package, run:

CentOS/Fedora
sudo dnf install nvme-cli

Ubuntu
sudo apt-get install nvme-cli

With Ubuntu probably you need to add the PPA to your sources.

sudo add-apt-repository ppa:sbates
sudo apt-get update

install-nvme-cli

Please take a note that the Linux kernel version is at least 3.3 and that you have the Linux NVMe drivers installed. NVMe devices should show up under /dev/nvme*

According to the technical documentation, the NVMe drives supports operating temperatures from 0°C – 70°C.

About NVMe
VM Express, NVMe, or Non-Volatile Memory Host Controller Interface Specification (NVMHCI), is a logical device interface specification for accessing non-volatile storage media attached through PCIe bus. NVM-Express is a quick, climbable host controller interface designed to address the needs for PCI Express technology based solid state drives.
The modern NVMe drives, on the other way, provide general speeds as high as 3500MB/s. That’s 5x over SATA SSDs and 10x over SATA drives!