Howto: ssh automatically add new hosts to the list of known hosts

When managing many hosts, answering 100s of “yes” can make us crazy. In a trusted environment, let ssh automatically add the new hosts to the list of known hosts and free us from typing “yes”es. How to enable it? Method 1. Passing option to ssh ssh -o StrictHostKeyChecking=no username@host Method 2. Configuring ~/.ssh/config To automatically […]

Pass-less ssh auto-login problem

I configured the Linux password-less automatic ssh login as in www.fclose.com/b/linux/1500/enabling-password-less-ssh-login/ . However, it still does not work for me. Any method to check it? The log in log /var/log/secure may give some clue on it. For example: Aug 20 23:16:10 doppler sshd[11143]: Authentication refused: bad ownership or modes for directory /home/useraaa tells us that the […]

A List of Common Software on Windows

Quick links to some useful software on Windows including Web browsers, Video/audio player and ssh/scpsftp/vnc tools for connecting to Linux. ssh/scp/sftp/vnc for connecting to Linux ∞ For Linux users, it is sometimes unavoidably to use Windows. With Windows, the Linux users will need to connect to Linux for some tasks. Some general software are needed. […]

How to Change Linux Account Password Through SSH: A Beginners’ Tutorial

People are sometimes given access to Linux/Unix and asked to change their initial passwords. But for beginners, changing a Linux/Unix password is not an easy task, especially when there is only SSH log on allowed to the Linux/Unix server. This post introduces how to change password of user USER on host HOST remotely using SSH. […]

How to Force Linux to Unmount a Filesystem Reporting “device is busy”

Linux may report “device is busy” when we try to umount a filesystem. This behavior is reasonable as it can help us avoid data loss by disallowing unmouting a filesystem when it is being used. But for situations when we are sure there is something wrong happened or we care not data lost such as […]

How to Disable and Enable Laptop Keyboard in Linux

Attaching a USB keyboard to a laptop is common when using a laptop because a normal keyboard may provide a more convenient typing experience. The laptop keyboard is not used in these situations. However, the laptop keyboard may still be touched by accident. In this post, we will discuss how to disable and enable the […]

Three Methods of Executing Commands on Many Nodes in Parallel via SSH on Linux

It is common to execute commands on many nodes/hosts via SSH for managing a cluster of Linux servers. On Linux, there are many choices for this task. Generally, to run commands on many nodes, there are two modes: serial mode and parallel mode. In serial mode, the command is executed on the node one by […]

Notes for Beginners of Software Development on Linux

Linux is a great platform for software development targeting servers or backends. In general, working on Linux is very productive. The problem that beginners on Linux face is the the learning curve is steep at the beginning. But believe me, after you get through the initial green steep learning step as in the figure below […]

How to Keep Linux SSH Session Alive from Disconnecting – Server and Client Side Fixes

SSH is a very common tool for Linux/Unix platforms. One annoying problem when using SSH is that the connection may get disconnected if the SSH connection is idle for some time under common configurations. Users may run an infinite loop like while true; do uptime; sleep 30; done when there is no work to be […]

SSD Enabled For DreamHost Shared Hosting: Simple Performance Measurement

As you may know, SysTutorials is hosted by DreamHost and we are quite satisfied with DreamHost. Now, DreamHost turns to be the first big player that enables solid state drives (SSD) for its Linux-based shared hosting plan in the shared hosting market and we are happy to enjoy the improvement. SSD is common for VPS […]

Lazy Linux Admins Going to Server Rooms Less: Forced Reboot, Auto Reboot after Kernel Panic and Email Notification after Reboot

Having to go the the server room to reset servers is the most headache thing for admins managing a cluster of Linux servers in a remote site. Either you can ping the server but can not ssh to it, or you even can not ping it. There are various reasons that may cause a Linux […]

MPlayer over SSH to Play Movie from Remote Host

MPlayer is a great movie player. SSH is a great tool to connect and transfer data over the network securely. Combining these 2 great tools together will be greater. You may already has a small server storing some movies or videos or music and playing them on your laptop will be convenient. In this post, […]

Hadoop Installation Tutorial (Hadoop 2.x)

Hadoop 2 or YARN is the new version of Hadoop. It adds the yarn resource manager in addition to the HDFS and MapReduce components. Hadoop MapReduce is a programming model and software framework for writing applications, which is an open-source variant of MapReduce designed and implemented by Google initially for processing and generating large data […]

Directly SSH to Hosts’ Internal IPs Through the Gateway

We have many hosts with internal/LAN IPs like 10.0.3.* behind a gateway and the hosts with LAN IPs can connect to the Internet through the gateway. We used iptables to forward port from the gateway to internal IPs so that users from hosts with Internet connections can SSH to the gateway’s forwarded port to log […]

Improving ssh/scp Performance by Choosing Suitable Ciphers

Update on Oct. 9, 2014: You should be aware of the possible security problems of blowfish and it is suggested not to be used. Instead, you may consider ChaCha20 as suggested by Tony Arcieri. To use this with OpenSSH, you need to specify the Ciphers in your *.ssh/config* files as chacha20-poly1305@openssh.com possibly with another default […]