Category Archives: Linux

How to tar and untar files and folders in Linux

Here is a quick cheat sheet how to compress and extract files/folders in CentOs Linux.  If you are extracting to a specific folder you have to create the folder ahead of time with mkdir /tmp/data/ or the command will not … Continue reading &r...

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How to configure a redis 2.8 cluster in CentOS 6.7

I have been involved in rolling out the Cherwell ticketing system and I thought I would share some notes around the Redis configuration.  Redis is used when you install Cherwell in a high availability mode.  It is used to store … Continue re...

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iPerf Network performance comparison between Virtual Machines on ESXi6

I finally found some time to run a series of iPerf network performance tests between Windows server 2008 R2, Windows 2012 and a Linux Debian virtual machines. The tests compare bandwidth throughput between vmxnet3, e1000 going through a 1Gbit and &he...

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Detecting Ephemeral Port Exhaustion in Windows 7 / 8 / 2012

Ephemeral ports are ports that start at a higher range then regular ports. For example when compared to a web server that listens on port 80, ephemeral ports start from 49152 for Windows 2008 R2.  If there are scripts or … Continue reading &r...

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Set up and troubleshoot SNMP on an ESXi 5.5 host

Here are some quick notes how to troubleshoot and set up SNMP on an ESXi host. The below also includes how to install snmpwalk and request info from an snmp server. STEPS HOW TO PROPERLY SET UP SNMP ON AN … Continue reading →...

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Testing TCP/UDP port connectivity in VMware ESXi 5.x Host

There may be times when you need to test TCP/UDP port connectivity from an ESXi host, here are some useful netcat commands. If you see no output from these commands it means the connection failed. Test TCP Port 902: ~ … Continue reading →...

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How to add a cron job to VMware ESXi 5.x

Here is a quick way that you can add a cron job in ESXi 5.x. You will notice that there are already jobs in here that run on a schedule by default, the last line is new. Edit the below … Continue reading →...

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Configure an SMB server accessible without a user or password in RedHat / CentOS

Here is a quick way to configure an Samba server accessible by everyone without a username or password.  The below has been tested in CentOS 6.5. Install the Samba service and create a directory yum -y install samba mkdir /mysamba … Continue ...

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Configure a basic postfix mail server between two CentOS Linux machines

How to Configure a basic postfix mail server between two CentOS servers Config file: /etc/postfix/main.cf #myhostname = host1.example.com #UNCOMMENT #mydomain = example.com #UNCOMMENT #myorigin = $mydomain #UNCOMMENT #inet_interfaces = all #UNCOMMENT...

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Using TCP Wrappers hosts.allow and hosts.deny to secure RedHat / CentOS

RedHat / Centos and other similar Linux distros have 3 layers of protection that can restrict access to services (Iptables, TCP Wrappers (hosts.deny, hosts.allow) and SeLinux). When a machine on a network requests access to a specific service it firs...

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