Postfix: send email using another Postfix

Some host providers block all email ports (like TCP/25 and TCP/587). Here’s simple of example of how to setup two STMP servers, where SMTP1 is a relay server (forwarder), and SMTP2 uses SMTP1 to send email. Both are using default configuration files with slight changes.

SMTP1 (smart host)

This config line allows SMTP2 to send email without SMTP authorization. For the sake of security it would make sense to restrict access to port 2525 using iptabes.

mynetworks = 127.0.0.1 <IP_of_SMTP2>

This goes to /etc/postfix/main.cf.

And the following

2525 inet n - n - - smtpd

goes to /etc/postfix/master.cf on SMTP1. So that Postfix opens TCP port 2525.

SMTP2

Add this to /etc/postfix/main.cf on SMTP2.

smtp_always_send_ehlo = yes<br />relayhost = 199.101.134.4:2527<br /><br />

After restart you should be able to send emails from SMTP2 via SMTP1‘s using port 2525.

mysql: backup from remote host using ssh

Sometimes you need to dump a mysql database, and there’s no free space on the server. Here’s you can do to back up the database:

ssh -p <ssh port> user@host "mysqldump -u dbuser -ppassword dbname | gzip -9" > database.sql.gz

At the end you will get mysq database on a local server. Although ssh is slow and it would take some time to transfer the database.

Adaptec RAID controller: how to get rebuild status

[root@host ~]# arcconf getstatus 1
Controllers found: 1
Logical device Task:
 Logical device : 0
 Task ID : 100
 Current operation : Rebuild
 Status : In Progress
 Priority : High
Percentage complete : 0

Command completed successfully.
[root@host ~]#

How to get SVN revision number using the SVN 1.7 database

As easy as:

[root@web ~]# sqlite3 /var/www/wordpress/.svn/wc.db
SQLite version 3.7.17 2013-05-20 00:56:22
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
sqlite> SELECT "changed_revision" FROM "NODES" ORDER BY changed_revision DESC LIMIT 1;
586
sqlite>
[root@web ~]#

Solving “Can’t locate File/Which.pm in @INC (@INC contains: /usr/local/lib64/perl5 /usr/local/share/perl5 /usr/lib64/perl5/vendor_perl /usr/share/perl5/vendor_perl /usr/lib64/perl5 /usr/share/perl5 .)”

To solve this problem:

 Can't locate File/Which.pm in @INC (@INC contains: /usr/local/lib64/perl5 /usr/local/share/perl5 /usr/lib64/perl5/vendor_perl /usr/share/perl5/vendor_perl /usr/lib64/perl5 /usr/share/perl5 .) 
 BEGIN failed--compilation aborted

you just need to install perl-File-Which package:

yum install perl-File-Which

php: hiding email header X-PHP-Originating-Script

By default PHP exposes information about the script which sent an email:

X-PHP-Originating-Script: 2000:send-email.php

To fix this change the following settings:

mail.add_x_header = Off
expose_php = Off

The header should be gone now. Have a nice day!

svn: Solving ‘svn: Error converting entry in directory ‘.’ to UTF-8′ error

If you get

# svn update
 svn: Error converting entry in directory '.' to UTF-8

run the following to get it working:

# export LC_CTYPE=en_US.UTF-8

 # svn update

Centos 7: how to monitor monthly bandwidth

To check how much bandwidth a server uses it would make sense to use vnstat. Let’s install it:

# yum install vnstat

Enable auto start after reboot:

# systemctl enable vnstat.service

After some time you can check data:

# vnstat

Linux: setting timezone to GMT

cp /etc/localtime /etc/localtime.default
ln -s /usr/share/zoneinfo/GMT-0 /etc/localtime

Here’s an example:

[root@d1 ~]# date
Sun Feb 12 10:24:25 CST 2017
[root@d ~]#

[root@d1 ~]# date
Sun Feb 12 16:24:51 GMT 2017
[root@d1 ~]#

bash: round float number / get integer

Bash can handle getting integer from float very easily:

[root@i ~]# cat ./f_to_i.sh
#!/bin/bash

f=20.3
i=${f%.*}

echo "float: " $f
echo "integer: " $i
[root@i ~]#

[root@i ~]# bash ./f_to_i.sh
float: 20.3
integer: 20
[root@i ~]#

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