Openbsd – nixCraft

How to allow root login from one IP address with ssh public keys only

June 10, 2017in CentOS, Debian / Ubuntu, FreeBSD, Linux, Openbsd, RedHat and Friends, Suse, UNIX last updated June 10, 2017

I am using MacOS on the desktop and Ubuntu Linux on the server. I disabled root login over ssh and enabled ssh based public key login. However, I recently added second Ubuntu server. I need to sync file between two using rsync command. Is there any way that I can log from the second server into my first server with root user from second server IP address only ([email protected] }# ssh [email protected]) without reducing OpenSSH server security option?

How to disable ssh password login on Linux to increase security

February 17, 2017February 17, 2017in CentOS, Debian / Ubuntu, Linux, Openbsd, RedHat and Friends, Security, Suse last updated February 17, 2017

I want to disable ssh clients from accessing using the password and only allow ssh login using SSH keys. How do I disable password authentication for SSH on Linux operating systems?

How to install denyhosts on Ubuntu Linux 16.04 LTS ( intrusion prevention security tool )

February 12, 2017February 12, 2017in Debian / Ubuntu, Linux, Openbsd, Security, Ubuntu Linux last updated February 12, 2017

I host my blog in cloud server, and I set up ssh to manage my Ubuntu Linux 16.04 LTS server. However, I noticed lots of break in and brute-force attacks on my ssh server? How can I stop hacking attempts into my system?

Linux/Unix: Force ssh client to use only password auth authentication when pubkey auth configured

January 21, 2017January 21, 2017in CentOS, Debian / Ubuntu, FreeBSD, Linux, Openbsd, RedHat and Friends, Suse, UNIX last updated January 21, 2017

I configured and use my openssh server to accept only public key based authentication. I need to test if my server accepting password. How to allow ssh client to use only password auth when pubkey auth configured?

How to fix: MacOS keep asking passphrase for ssh key after upgrade or reboots

January 16, 2017January 17, 2017in Mac OS X, Openbsd, UNIX last updated January 17, 2017

I recently upgraded my MacOS Sierra and now ssh command keep asking for passphrase as follows when I try to login to my remote Linux/Unix server:
Enter passphrase for key ‘/Users/vivek/.ssh/id_ed25519’:
How do I fix MacOS Sierra upgrade that keep breaking ssh keys in terminal?

How to change the ssh port on Linux or Unix server

January 6, 2017in Debian / Ubuntu, FreeBSD, Linux, Openbsd, RedHat and Friends, Suse, UNIX last updated January 6, 2017

I am a new Linux/Unix server admin. How do I change the SSH Port for my Linux or Unix server using command line option?

How to apply patches on OpenBSD system/kernel and packages easily

August 29, 2016September 20, 2016in Openbsd, Package Management, Security, UNIX last updated September 20, 2016

I am a regular Linux system user. In Linux (especially CentOS), I am used to applying updates a few times a week using yum command, but how do I do that on my OpenBSD severer? How do I apply updates on OpenBSD operating system?