How to setup Postfix relay with authentication in CentOS 7

To configure postfix to relay mail using another MTA, you may do the following steps:

postconf -e 'relayhost = smtp.to.relay.com'
postconf -e 'smtp_sasl_auth_enable = yes'
postconf -e 'smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd'
postconf -e 'smtp_sasl_security_options='

Replace smtp.to.relay.com with the original MTA hostname that you going to use for relaying. Now, create the sasl_passwd file in /etc/postfix with the following inside:

smtp.to.relay.com smtp_username:smtp_password

Now, use postmap to generate postfix hash db:

postmap /etc/postfix/sasl_passwd

You can verify if it’s working with the following:

postmap -q smtp.to.relay.com /etc/postfix/sasl_passwd

This will return the username and password for your smtp relay host.

Now all you need to do is to restart the postfix

service postfix restart

How to Stop Redirecting All Traffic Trough OpenVPN

There are cases, where you might want to use OpenVPN to redirect only a fraction of traffic, but not all. By default, after you connect to OpenVPN, server would push the call 'redirect-gateway' to the client to make the client divert all the traffic through tun network.

This behavior can be override with the following command line argument:

--pull-filter ignore redirect-gateway

You can add it in the openvpn command line as following:

openvpn --pull-filter ignore redirect-gateway --config "your_file.ovpn"

Once this is done, remember that, you have to route the targetted traffic using either the route command or 'ip route' command, otherwise no traffic will route through your openvpn tunnel network.

How to Save OpenVPN Username & Password

If you are using OpenVPN in a Linux platform through command line, it is always handy to be able to save the authentication information in a file and let openvpn use them. There are two ways you can do it.

First Method

First save the password in a file e.g auth.txt with two lines:

username
password

First line is for username and the second line is for password.

If you are using .ovpn files for configuration, open the .ovpn file and simply add the following:

auth-user-pass auth.txt

Now, your authentication would use the authentication given in that file

Second Method

You may add the auth-user-pass in the openvpn command line argument, but you have to make sure, this is passed after the --config. Here is an example

openvpn --config "your_file.ovpn" --auth-user-pass "auth.txt"

That should be enough.

How to Add Custom Sale Order Line in Odoo 12

There are two ways you can add custom sale order line in Odoo 12.

First Method

You can search the sale order first with the name or browse with the ID

sale_order = self.env['sale.order'].search([('name', '=', 'SO009')])

Now, you can see the sale order line IDs using the following:

sale_order.order_line

As this is a One2many relation, we need to use a tuple in the Odoo ORM write() method. Here is the list of data you can pass in a tuple to change data that has One2many or Many2many relation

Odoo ORM Documentation

You can now pass this as python dictionary for ‘order_line’ to sale.order of desired product as following:

sale_order_new.write({
'order_line': [
(0,0, {
'order_id': sale_order.id,
'product_id': 2003,
'price_unit': 3000.0,
'product_uom_qty': 2.0,
'name': ''
})
]
})

Second Method

In this method, you can simply define the order dictionary, and create a sale.order.line item with the order_id in reference. Here is an example

# define dictionary to add order_line
order_line_dict = { 'order_id' : 9, 'product_id': 2003, 'price_unit': 3000.0, 'product_uom_qty': 2.0, 'name': '' }

# search the order line for the sale order
sale_order_line = self.env['sale.order.line'].browse(9)

# create a new order line
sale_order_line.create(order_line_dict)

# print sale order lines
sale_order_line

Note

If you are doing/testing this on the Odoo Shell, then make sure to run the following after the changes to reflect on database:

self.env.cr.commit()

Odoo doesn’t call database cursor commit if you are coding on Odoo shell, it calls automatically though if you are doing it in a module. Just a friendly reminder!

Troubleshoot: -bash: fuser: command not found

If you are trying to use a command, fuser, that is used to identify process using lock file or socket file, and having the following error:

-bash: fuser: command not found

that means, your system doesn’t have the psmisc package installed. Usually, killall, fuser type of commands are under this package. CentOS 7 sometimes, do not install the package by default. To install it, run the following:

yum install psmisc -y

Once done, you should be able to use fuser command.

How To: Use SSH Password in a Script

You can obviously use RSA public/private keypair to access servers without password, although, sometimes, it may be desirable to use ssh password on a command line and run a remote command on another server. This can be done using a tool called ‘sshpass’. You can create a simple bash script using sshpass, that can help you monitor and control multiple servers from a single location.

How to use ssh password in script

First install sshpass:

# yum install sshpass -y

Once done, you can use sshpass command as following:

# sshpass -p "SSH_Password" ssh -o StrictHostKeyChecking=no SSH_Username@remote-ssh-server "yourcommand"

Just replace, the password, username, remote-ssh-server and your command with your desired setup, and viola!

Note: If yum says, the following:

No package sshpass* available.

then you would need to install epel repository to install sshpass. To install epel, run the following:

# yum install epel* -y

Programming: How To Check if an IP is Available or Not in Bash

How To Check if an IP is Available or Not in Bash

A quick trick I use is ‘ping’ command. PING will return 0 on success and 1 or above on failure while using it with -c 1 (Means only one ICMP packet). That makes it useful to use with a if condition shell code as following:

if ping -c 1 -w 5 192.168.2.1 >/dev/null
then
echo "IP Available"
else
echo "IP Not Available"

Programming: How to Check If A File Exists or Not in Bash Script

How to Check If A File Exists or Not in Bash Script

You can use if condition in bash script to do that. If conditions takes ‘-f’ to test if a file exists or not. Syntax would be the following:

$FILE = $1
if [ -f $FILE ]; then
echo "File Exists"
else
echo "File Do Not Exist"
endif

Now, if your script only demands to check if the file do not exist, you can use a unary operator for negate the boolean value as following:

$FILE = $1
if[ ! -f $FILE ]; then
echo "File Do Not Exist"
endif

 

How To: Restrict a Folder to Your IP Only

Sometimes, for development purposes, you may want to restrict access to the folder, only to your IP, and deny others from accessing that folder. One way to do that is to use htaccess rules. A common rule, could be denying all the users and allowing your IP. To find out, your IP, you may visit the following:

http://ifconfig.co

Note the IP it has reported. Open the folder that you want to protect. Find the .htaccess file under the folder (If no file available, create one) and add the following:

order deny,allow
deny from all
allow from <your IP goes here>

Replace the <your IP goes here> from the snippets with the IP you have noted from ifconfig.co. Now, your folder should be accessible only from your IP.

Programming: Laravel Error – Specified Key Was Too Long

A common error I have seen users reporting using Laravel, is the following:

SQLSTATE[42000]: Syntax error or access violation: 1071 Specified key was too long; max key length is 767 bytes

The error actually happens because Laravel 5.5 assumes you have MySQL 5.7.7 or above. While on MySQL 5.7.7 the key size was increased than the older versions.

How to fix laravel Specified key was too long

To fix this, find the AppServiceProvider.php file under app/Providers folder, and add the following line before start of the class:

use Illuminate\Support\Facades\Schema;

Then, inside the boot() method under the class, add the following line:

Schema::defaultStringLength(191);

If you restart your laravel migration or the query, it should work fine now.