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Linux Server

knackforge blog

How to install and configure Zabbix 3 on Debian 8 (Jessie)

Zabbix is enterprise open source monitoring software for networks and applications. It is designed to monitor and track the status of various network services, servers, and other network hardware. The zabbix server can check standard networking services like HTTP, FTP, SMTP, IMAP etc. We need to install and configure a Zabbix agent  for gathering data about CPU, disks, internal system process, RAM, etc.

Lets check the steps for installing and configuring Zabbix on a Debian 8 server:

Step 1: Install required dependencies:

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knackforge blog

Restoring removed files (rm -rf) in Linux with TestDisk

There are odd times where we would have accidentally deleted some important folders without having any actual backup. It happened to us, one of our team members on the way to remove a symbolic link, accidentally deleted a webfolder using rm -rf, though we normally maintain GIT repo, for this temporary project, we did not. So we had to restore it though initially it looked gloomy. I stumbled upon "extundelete" but that could not restore any important files. Then we tried http://www.cgsecurity.org/wiki/TestDisk. See more details below

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knackforge blog

How we managed to use Tripwire for detecting intrusions

We all should be aware that security is very important for our servers. Having informed about the changes to server file system is always important, as unauthorised access could very well breach security. Here comes our saviour Open Source Tripwire, which is a free security and data integrity tool useful for monitoring and alerting on specific file change(s) on a range of systems. 

Open Source Tripwire functions as a host-based intrusion detection system. It detects changes to file system objects and alerts the server administrator.

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knackforge blog

Quickly setup Mailman mailing list with Exim 4 for a subdomain

Goal: to setup mailing lists - listname@subdomain.yourdomain.comResources Required / Assumptions:

  • An ubuntu/debian based server with no email servers configured already (no MTA is working already) -- should have a static IP [note: redhat/fedora based should also work fine, but the installation commands & configuration file paths may vary]
  • A domain-name, with DNS record access (note that you could use the steps explained to setup mailing lists on main domain as well, not just on subdomains)

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knackforge blog

Fix chkconfig command not found

It happened in one of the servers we maintain, chkconfig was installed but it couldn't be loaded. Below are the sequence of commands I used to find the cause and fix.

[[{"type":"media","view_mode":"media_large","fid":"104","attributes":{"alt":"","class":"media-image","typeof":"foaf:Image"}}]]

# It was needed to have tomcat start at boot time

$ sudo chkconfig --add tomcat  
-bash: chkconfig: command not found

# I thought it was not installed but it is in place.

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knackforge blog

Preventing SSH idle connection timeout (Linux)

If you are a Linux-Based developer & had to access servers through SSH, one of the most common issues you'd face is that your SSH connection gets timed out (disconnected) if you don't use it for some time.To prevent connection timeout, just add the line below to /etc/ssh/ssh_config:

ServerAliveInterval 60(the above command will PING the server every 60 seconds - so the server will keep the session active).

Have an uninterrupted working session!

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knackforge blog

Setup Default Group & Permissions for new files created under a specific directory [Debian/Ubuntu]

Say you have a directory that you want to share with multiple people with group-rw permissions and want to preserve this for newer files created on that directory.

The following quick steps could help you do that.

Let's assume your shared directory is: "/var/www/"

Step 1:

Install "acl" package (if not already installed)

sudo apt-get install acl

Step 2:

Enable "acl" option for the partition that contains the folder. Edit /etc/fstab and ensure that your partition has "acl" as one of the options.

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