WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!

Those who regularly build and rebuild machines or virtual machines on a dhcp network will probably be faced with this quite often, this is due to the known fingerprint for the previous host being different to a new one which has aquired the same IP address.

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @ @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY! Someone could be eavesdropping on you right now (man-in-the-middle attack)! It is also possible that a host key has just been changed. The fingerprint for the ECDSA key sent by the remote host is c5:ab:00:3c:88:7e:18:8f:46:49:1d:af:f1:8b:4e:98. Please contact your system administrator. Add correct host key in /root/.ssh/known_hosts to get rid of this message. Offending ECDSA key in /root/.ssh/known_hosts:66 ECDSA host key for 192.168.1.165 has changed and you have requested strict checking. Host key verification failed.

Monit is an application I’ve been meaning to setup for a while, I was first made aware of it from a chap I had the pleasure of talking to at OggCamp this year, he seemed to use it to the n’th degree to monitor files and services within docker containers to ensure a development environment was as it should be. This was far more than I really needed, but the monitoring of services definitely caught my attention so I set about installing and configuring. I was pleasantly surprised with the result, and how simple the whole process was.

A while ago I put together a post detailing the installation and configuration of 2 hosts running glusterfs, which was then presented as CIFS based storage.

http://jonarcher.info/2014/06/windows-cifs-fileshares-using-glusterfs-ctdb-highly-available-data/

This post gained a bit of interest through the comments and social networks, one of the comments I got was from John Mark Walker suggesting I look at the samba-gluster vfs method instead of mounting the filesystem using fuse (directly access the volume from samba, instead of mounting then presenting). On top of this I’ve also been looking quite a bit at ZFS, whereas previously I had a Linux RAID as the base filesystem. So here is a slightly different approach to my previous post.

I decided to try the upgrade process from EL 6 to 7 on the servers I used in my previous blog post “Windows (CIFS) fileshares using GlusterFS and CTDB for Highly available data”

Following the instructions here I found the process fairly painless. However there were 1 or two little niggles which caused various issues which I will detail here.

The servers were minimal CentOS 6.5 installs, with Gluster volumes shared via CTDB. The extra packages installed had mostly come from the EPEL or Glusterfs repositories, and I believe this is where the issues arise - third party repositories.

Gone are the days where we install nslookup for DNS resolution testing, the new(ish) kid on the block is dig. Although maybe not installed by default, it can be installed quite easily from yum, however it comes bundled with a number of tools so the package name isn’t all that obvious.

[root@server ~]# yum install bind-utils

Will do the trick, now how to use it?

[root@server ~]# dig @nameserver address.com

Here’s a (very) quick howto showing how to get GlusterFS up and running on Fedora. Its probably better situated on a distro like CentOS/RHEL, Ubuntu Server LTS or Debian stable but where’s the fun in knowing it won’t break? Most of these commands are transferrable to other distros though, its Fedora centric due to the use of yum, selinux and systemd (systemctl).

Pre-requisites: 2x (or more) servers running Fedora, I used 18 in this example but i’m sure it shouldn’t change a great deal for newer releases. If it does I’ll try update this doc. The idea behind this setup is to use 2 servers as hypervisors (KVM) and have local storage but reslience, I won’t be covering the virtualisation side, purely storage so VM’s will be adequate for this setup.

So this coming Monday will be the 2 year anniversary of the Rossendale Linux User Group, not too shabby really. Not marking the occasion or anything but I’m going to be running a talk/demo on virtualisation under Linux. Seems to be the pet project I’ve worked on the most so have a fairly polished setup to talk about. But why make it easy on myself? I normally use CentOS for server builds but just for a change, as it seems to be the way I’m heading, I decided to give Ubuntu a shot.