503 Service Unavailable : PHP-FPM issue

Error: 503 Service Unavailable The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later.

Solution: 

systemctl start php80-php-fpm (if face the error follow the next command )

systemctl status php80-php-fpm.service

ERROR: unable to bind listening socket for address '127.0.0.1:9000': Address already in use (98)

netstat -tulpn | grep -w 9000 

tcp        0      0 127.0.0.1:9000          0.0.0.0:*               LISTEN      884/php-fpm: master 

kill 884

systemctl start php80-php-fpm

Note: Use your PHP version, PID and Port in the command. if netstat not works install net-tools first: yum install net-tools

How to Install PHP 8.0/8.1on Linux Centos 7

Method-1 for PHP 8.0

Remi Repository

# yum install -y https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm

# yum install https://rpms.remirepo.net/enterprise/remi-release-7.rpm

PHP 8.0 install
# yum install -y --enablerepo=remi-php80 php php-cli

Exntesions:
#yum install -y --enablerepo=remi-php80 php-mysqlnd

Method-1 for PHP 8.1

yum -y install https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
yum -y install https://rpms.remirepo.net/enterprise/remi-release-7.rpm
yum -y install yum-utils
yum-config-manager --disable 'remi-php*'
yum-config-manager --enable remi-php81
yum repolist
yum -y install php php-{cli,fpm,mysqlnd,zip,devel,gd,mbstring,curl,xml,pear,bcmath,json,opcache,redis,memcache}

How to test PowerMTA SMTP using telnet

telnet localhost 25

ehlo localhost

mail from: username@from-domain.tld

rcpt to: username@to-domain.tld

data

Subject: PMTA SMTP Check

This is just an SMTP conf Check. You may disregard.

.

quit

tail -f /var/log/pmta/pmta.log

pmta show queues

How to Send an email using Telnet in CentOS

sudo apt install telnet

sudo yum install telnet

telnet targetserver.tld 25

HELO sourceserver.tld 

MAIL FROM: username@sourcedomain.tld

RCPT TO: username@example.com

DATA 

Subject: Sending an email using  SMTP through telnet 

Hi, 

This is just a Test Email ? You may disregard this? 

regards;

Mr. Y

.

Note: We can start writing some subject and body. To do that we need to use the DATA command. First type DATA followed by Subject: and the body. Once done, enter " . "  (without quote)to send the email to be queued.

Stop and Disable Firewalld on CentOS 7

sudo firewall-cmd --state

sudo systemctl stop firewalld

sudo systemctl disable firewalld

sudo systemctl mask --now firewalld

Create and Install Self-Signed SSL Certificate on CentOS

yum install openssl

mkdir /etc/[webserver]/ssl

openssl genrsa -out “/etc/[webserver]/ssl/example.key” 2048

openssl req -new -key “/etc/[webserver]/ssl/example.key” \ -out “/etc/[webserver]/ssl/example.csr”

Country Name (2 letter code) [AU]:xx

State or Province Name (full name) [Some-State]:xx xx

Locality Name (eg, city) []:xx

Organization Name (eg, company) [Internet Widgits Pty Ltd]:xx

Organizational Unit Name (eg, section) []:xx

Common Name (e.g. server FQDN or YOUR name) []:example.com

Email Address []:xxx@gmail.com

openssl x509 -req -days 365 -in “/etc/[webserver]/ssl/example.csr” \ -signkey “/etc/[webserver]/ssl/example.key” \ -out “/etc/[webserver]/ssl/example.crt”

Add Domain specific DKIM in PMTA config

#MTAs

<virtual-mta ip1>

    smtp-source-host 192.198.0.1 host.domain.tld

    <domain *>

        max-msg-rate 400/h

    </domain>

</virtual-mta>

#DKIM Keys

domain-key key1,domain1.tld,/etc/pmta/keys/key1.domain.tld

domain-key key2,domain2.tld,/etc/pmta/keys/key2.domain.tld

domain-key key3,domain3.tld,/etc/pmta/keys/key3.domain.tld

#Specify the DKIM for specific Domain using Directive

<domain domain1.tld>

    dkim-sign yes

    smtp-hosts [127.0.0.1]:587

    dkim-identity @domain1.tld

</domain>

<domain domain2.tld>

    dkim-sign yes

    smtp-hosts [127.0.0.1]:587

    dkim-identity @domain2.tld

</domain>

<domain domain3.tld>

    dkim-sign yes

    smtp-hosts [127.0.0.1]:587

    dkim-identity @domain3.tld

</domain>

#CALL PMTA POOL for Rotation

<virtual-mta-pool pmta-pool>

    virtual-mta ip1

</virtual-mta-pool>