My Linux Guide

Network Manager

How To Import WireGuard VPN to Network Manager vpnconfigfile="/path/to/your/wg0.conf" vpnName="myvpn" sudo nmcli connection import type wireguard file "${file}" nmcli connection modify wg0 connection.id "${vpnName} nmcli connection modify wg0 connection.interface.name ${myVPN} # if you want to

Script to update all dockers running on a machine.

This is a script i wrote to manage updates on a number of containers that i run within a directory. The pre-requisite for this script to be used is that you have all your docker-compose.yml files within a directory. They can be within their own folders. Just sharing so

SIOCSIFFLAGS: Operation not possible due to RF-kill

Apparently some linux distros soft block bluetooth and wifi by default. If you get this error message : SIOCSIFFLAGS: Operation not possible due to RF-kill Then that may be because the wireless adapters have been soft blocked. You can check for this by issuing the command: rfkill list If the adapters

Containers

Install Docker on Centos 7

Install Docker: yum install docker docker-registry systemctl enable docker.service systemctl start docker.service systemctl status docker.service Install Docker Compose: curl -L "https://github.com/docker/compose/releases/download/1.23.2/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose chmod +x /usr/local/

Ntpdate Not syncing time correctly – Xen Host

I came across a situation where ntpdate would not sync the time correctly in a Xen Virtual machine. The time was 10 minutes ahead of what it was supposed to be. Apparently , you need to force it to not use the dom0’s clock. vi /etc/sysctl.conf xen.independent_

Apache

Apache is running a threaded MPM, but your PHP Module is not compiled to be threadsafe.

You may come across this error in newer version of apache which is because the newer configurations use an event based Multi Processing Module by default. If the PHP is not compiled with threadsafe, you will need to switch to the prefork MPM, which does not use threads. Apache is

NFS Version 4 Export

Install the required Packages: yum install nfs-utils nfs4-acl-tools portmap Export the folder to share: echo "/folder/to/share IpAddressToShareWith(rw,no_root_squash,async,fsid=0)" >> /etc/exports Map NFS User for ownership: vi /etc/idmapd.conf Domain=YourDomain.com Nobody-User=apache Nobody-Group=apache Iptables Rule

SSL Root Certificate update in Linux for curl

When you use curl in Linux machines to make remote calls to SSL sites, you need to have latest root certificates installed. Recently I came across a situation where the newer root certificate were not available and so the remote call suddenly started failing. First, you will have to find

Systems Administrator

Processes in Linux

D : This means the process is in uninterruptible sleep mode. Usually Input and output are in this mode. R : Currently Running Process or is in the running queue. S : Is in sleep state waiting for an event to complete. T : Means the process is stopped by a signal. X : X

git

GIT Common Commands and How Tos

To Discard Changes which have not yet been indexed to server , run this command : git stash save --keep-index git stash drop To Clone Git Repo on the local filesystem git clone file:////path/to/repo/project.git/ .

PHP

PHP function to remove whitespaces from a string

Usage : $spaceRemovedString = removeWhiteSpaces($stringWithSpace); Function : function removeWhiteSpaces($spaceStr) { $newStr = preg_replace('/\s+/', '', $spaceStr); return $newStr; }

Systems Administrator

Repairing Accidental Damage to file system permissions and ownership

There are cases when you might accidently change the system permissions and you want to revert it back to default permissions. You can revert ownership and permissions on installed packages by using rpm or you can copy permissions from a clone machine if you have one. Copying permissions and resetting

Systems Administrator

Handling Multiple SSH Keys and Ports for Multiple Machines

You might have to deal with a lot of machines with different keys and ports. Here is a simple way to make that easier. Edit / Create ssh config file. vi ~yourUserName/.ssh/config Put the information about your hosts into the config file: Host server1.example.com HostName server1.example.

Systems Administrator

Setting up Git on Centos

In this tutorial, I am showing how to setup GIT on Centos with SSH . Packages to be installed : yum install git-core gitosis Create user and group which will own the repositories : useradd -d /path/to/repositories gituser Generate or copy a ssh key for use with git : su gituser ssh-keygen

Network

Adding a Secondary Gateway / Static Route in Linux

In order to create a static Route you can enter the following command : ip route add 192.168.1.0/24 via 192.168.1.254 dev eth0 or route add -net 192.168.1.0 netmask 255.255.255.0 gw 192.168.1.254 dev eth1 Note : In

Systems Administrator

Installing and uninstalling redmine plugins

Download the plugin and extract it into the plugins directory. Go to the plugins directory and run : bundle install --without development test RAILS_ENV=production If you need to migrate the database then run the following command : rake redmine:plugins:migrate RAILS_ENV=production Now restart redmine : touch /path/to/

Systems Administrator

Installing Redmine with Passenger and Apache on Centos 6.3

1. Install prerequisite / dependencies : yum install subversion make gcc gcc-c++ zlib-devel ruby-devel rubygems ruby-libs apr-devel apr-util-devel httpd-devel mysql-devel mysql-server automake autoconf ImageMagick ImageMagick-devel curl-devel 2. Go to the directory where you want to download Redmine Code and check out the files using svn command : svn co http://svn.redmine.org/

IPtables

Port Forwarding with Iptables

You can use port forwarding in iptables, to forward a port to private ip , here is how you can do that : iptables -t nat -I PREROUTING -p tcp -d <listenip> --dport 22 -j DNAT --to <ipToForwardTo>:22 iptables -I FORWARD -p tcp -d <ipToForwardTo>

Systems Administrator

Setting Default permissions on installed packages

If you mess up the permissions on installed packages some how , you can set default permissions by issuing the following command : for p in $(rpm -qa); do rpm –setugids $p; rpm –setperms $p; done

PHP

Function to write a message to a text file

Sometimes , we need to write some logging information to a text file in php. The following function takes filename and message as the parameter and logs whatever you pass to the file with date and time. function logToFile($fileName, $logMessage) { $logDirectory = “/path/to/log/dir”; $fileHandler = fopen($logDir . '/'

Shell Scripting

PAM Login Notification Centos

Edit the file : /etc/pam.d/sshd vi /etc/pam.d/sshd Add this line to the above file : session optional pam_exec.so /path/to/script.sh Now Create the Script that will send the notification : vi /path/to/script Paste The Following content, and adjust the admin email

Systems Administrator

Redhat Package Manager Tips & Tricks

View a List of packages installed by Date : rpm -qa --qf '%{INSTALLTIME} (%{INSTALLTIME:date}): %{NAME}-%{VERSION}-%{RELEASE}.%{ARCH}\n' | sort -n

Asterisk

Using Database to store VoiceMail with Asterisk

In order to use database as the storage for voicemails in asterisk, you would need to compile asterisk with odbc storage support. Dependencies : unixODBC yum install unixODBC Setup: Run make menuselect when making asterisk and make sure you select odbc_storage under voicemail build options. Edit voicemail.conf to have

Perl Scripting

Connecting To MySQL Using Perl

#!/usr/bin/perl use strict; use DBI; $host = "dbhost"; $database = "dbname"; $port = dbport; $tablename = "tablename"; $user = "dbuser"; $pw = "dbpassword"; $dbh = DBI->connect("DBI:mysql:database=$database;host=$host;port=$port",$user, $pw) or die "Unable to

Shell Scripting

Reference first argument in move command

mv /path/to/dir/filename.txt !#^:h/newname.txt Where : ! means history expansion # means command currently being typed ^ means the first argument :h gets the “head” that is the directory without the filename portion