After I update my CentOS 7 VM kernel, the new kernel stopped booting on my XenServer hypervisor. I’ve been using XenServer version 7.1
This tutorial explains how to install Tobias Oetiker’s Smokeping into /opt/smokeping on a CentOS 7 box. Features of Smokeping: – Best of breed latency visualisation. – Interactive graph explorer. – Wide range of latency measurement plugins. – Master/Slave System for distributed measurement. – Highly configurable alerting system. . Ready to install Smokeping. Settings: PERL5LIB = not set PERL = /usr/bin/perl The Smokeping Makefiles use GNU make functionality. Continue installation with. Install Smokeping. Before installing smokeping, you will need to install the Nginx web server with fcgiwrap and sendmail as its prerequisites. Introduction Tracking network latency should be an integral of anyone’s server management routine. It is essential that you monitor this regularly so you can get a better picture of your server’s health and performance. It can help you determine if your network is overloaded or indicate if there is an incorrect router configuration or downed.
Working Kernel version, before
And, after
yum update
was 3.10.0-693
And, after
yum update
Kernel version is 3.10.0-1127.19.1
This issue is due to the kernel which I updated has the
spectre/meltdown
patches in. But our XenServer 7 doesn’t. This difference created the kernel booting problem. Interestingly, this issue only affects CentOS VMs. My other Ubuntu servers can just run updates without issue but CentOS VM’s require the host to be updated or they stop working.To FIX this issue you should update your XenServer to the latest version or else if there are hotfixes available then you should install it.
Link for XenServer 7.1 hotfixes. https://support.citrix.com/article/CTX230788
To upgrade XenServer 7.1 you should have Citrix License first. But a “free” patch was released for 7.2, due to the massive security issue later.
But if you have been running older XenServer’s version, older than 7.1 then you don’t have any choice besides updating XenServer to the latest.
Also, CentOS fixed their booting problem on their new Kernel versions which I will discuss later below.
What is Meltdown and Spectre vulnerabilities?
Someone having access to the VM will be able to read the memory outside the VM itself, and therefore read data from other VMs on this same physical host. An attacker could enter via other application exploits (webserver etc.) on your VMs.
Am I affected?
Meltdown is using a design flaw into Intel CPUs only. This is called by Xen sec team ”SP3” (aka rogue data cache load).
You are impacted only if you are using:
You are impacted only if you are using:
- 64-bits PV type VM (HVM/PVHVM aren’t affected!)
- Intel CPUs (AMD chip design is a bit different and not affected)
- untrusted VMs, ie untrusted users having VM access (even non-root!)
- All XenServer versions are affected
64-bits PV guests are vulnerable because guest and hypervisor share the same address space, but with different privileges. HVM aren’t.
Mitigate Risk:
![Install Smokeping On Centos 7 Install Smokeping On Centos 7](https://www.tecmint.com/wp-content/uploads/2016/12/Install-TeamViewer-on-CentOS-7.png)
Permute 3 1 16. Migrate all VM’s from
But if you have been running older version XenServer, older than
PV
to HVM
or upgrade XenServer to latest or install hotfixes if available. But if you have been running older version XenServer, older than
7.1
then you have to update your XenServer to resolve this issue.Back to CentOS 7 booting issue.It seems the booting issue was fixed in the latest CentOS kernel versions. If the XenServer was up-to-date with the hotfixes then the VM’s should not have any problem. But in my case I didn’t update my XenServer, so now I’ve to either install the latest CentOS 7 kernel or downgrade to older previous running one.
Upgrading Kernel Version
Add
ELRepo Repository
first.Install office 365 on different drive. Add ELRepo gpg key to the system.
This is important – CentOS will not allow the installation of an unsigned software package. The GPG key provides a digital signature to verify that the software is authentic.
Now add new ELRepo repository.
Centos 7 Install Ifconfig
When it’s complete, check all repository enabled on the system, and make sure ELRepo is on the list.
kernel-ml – which indicates a mainline release, with a shorter support term but with more frequent updates.
Crack local administrator password server 2003. OR INSTALL (Install either ml or lt)
kernel-lt – signifying a stable long-term support release.
listout all your existing kernel version on your system.
We have sucessfully installed CentOS latest kernel version
4.4.234-1
. Now set this as a default kernel.Set Default Kernel Version
First listout all existing kernel versions.
NOTE: The first entry is denoted as
Zero
. Let us modify the Kernel Version to 4.4.234-1
which is at line number 1
but denoted as entry 0
.Set default kernel.
Need for speed most wanted 2012 exe file free download. Next,
Rebuild grub.cfg
file with 'gurb2-mkconfig'
command.Reboot Server
Above solution will resolves the booting issue.
If you don’t want to update CentOS kernel to latest one and want to boot from the existing previous working kernel then reboot your system and choose kernel version which was working fine before from
grub menu
and select enter
and follow the below steps.Set Default Kernel Version but first list-out all existing kernel versions.
NOTE: The first entry is denoted as
Zero
. So currently the Server is booted to 0th
entry as per the above command output. Let us modify the Kernel Version to 3.10.0-693
which is at line number 4
but denoted as entry 3
.Set default kernel.
Next,
Rebuild grub.cfg
file with 'gurb2-mkconfig'
command.Check default Kernel Version
Reboot Server
In this article we are going to setup smokePing to keep track of our network with latency monitoring. It can measure, store and display latency, latency distribution and packet loss. It comes with highly configurable alerting system and live latency charts and interactive graph explorers. Smokeping is not limited to testing just the roundtrip time of the packets. It can also perform some task at the remote end ('probe'), like download a webpage. This will give a combined 'picture' of web server availability and network health.
SmokePing Installation
SmokePing is an open source packets monitoring tool which comes with an easy installation and configurations. On a fresh Ubuntu 15.04 with its minimal installation we only need to get the basic web server’s libraries as its prerequisites.
Installing SmokePing and Pre requisites
The recommended webserver for smokePing is Apache, but we will setup and prefer with Nginx over Apache for performance and scalability.
So, First install Nginx web server with fcgiwrap and sendmail packages as below.
Fcgiwrap Setup with Nginx
Nginx can't serve CGI scripts by itself, so it requires a CGI server bound to localhost in order to make those accessible. Thats why we are using Fcgiwrap here for this.
Now modify the host you want or we can use the default host to support cgi scripts as follow.
By using below commands we create links from smokeping to www folder.
Once smokeping is running, it will generate rrd files that can be examined by the CGI scripts to produce html output.
SmokePing Configuration
After we had successful installation of basic packages, we move forward to configure its different files for monitoring hosts as follow.
Edit General Config file
Edit Pathnames file
Put the value as false for sendmail so that smoke ping can run if you are not using it.
Edit Alerts file
Install Kubectl On Centos 7
Edit the Targets file
Here we Add the targets that will measure by appending them to the bottom of the targets file. We add an entry starting with a + to create a top level entry, and subsequent lines with ++ that will show up as sub entries. These will be show up in a menu on the left of the generated web page like so:
Restart smokeping and Nginx Web server
Access smokeping on web
Understanding smokePing Latency
Centos 7 Install Gnome
All the information together gives an indication of network health. For example, packet loss is something which should not happen out of the blue. It means that a device in the middle of the link is overloaded or a router configuration somewhere is wrong.
Heavy fluctuation of the RTT (round trip time) values also indicate that the network is overloaded. This shows on the graph as smoke; the more smoke, the more fluctuation.
Conclusion
We have successfully setup and activate smokePing on Ubuntu by using Nginx Web Server. SmokePing is the basic open source network latency monitoring tool that every network administrator prefer to setup after its network setup.