This week I finally took the plunge and upgraded most of the servers I work with from PHP 7.1 to PHP 7.2. (Some of them still can't be brought forward due to dependencies that use mcrypt.) I ran into a few snags with the upgrade to 7.2 and thought I'd document them here. This may be useful if you:

• Run CentOS Linux 6.x,
• Want to install PHP 7.2,
• Need pthreads support in PHP, and
• Prefer to compile PHP from source

Executive summary

In order to build PHP 7.2 with pthreads on CentOS 6, you must upgrade autoconf to version 2.64 or higher, which must be done manually instead of via the yum package manager. You'll also have to first build PHP 7.2 without pthreads, then use this "bootstrap" copy to prepare the pthreads extension before compiling PHP a second time.

autoconf 2.69

Start by installing autoconf 2.69. The latest version available through yum is 2.63, which isn't sufficient to build PHP's configure script.

It's critical that you supply the --prefix=/usr option when...

This article outlines the deployment of a recursive, caching, authoritative DNS server running BIND 9.11.17 on CentOS 6.10. Why this combination? The BIND name server is the most feature-rich open source resolver, with decades of development behind it. And despite closing in on its nominal end-of-life, CentOS 6 remains a popular server OS due to its proven stability and the absence of systemd.

Preparing your environment

In order to set up your DNS server, you're going to need:

• A server running CentOS 6.10 (bare metal, VM, or VPS will all work)
• root ssh access to your server
• At least 64MB of available RAM for the named process
• wget or some other utility to download a file

There are also some software dependencies:

• The gcc compiler (yum -y install gcc)
• The file utility (yum -y install file)
• OpenSSL header files (yum -y install openssl-devel)

You don't necessarily ...

In an age where SSL/TLS certificates are free via Let's Encrypt, if you're running a Postfix mail server, you should make sure it's capable of speaking TLS.

Here's the output from postconf -n | grep tls on my machine, which lists all of the TLS options in main.cf that I've changed from their defaults:

    smtp_tls_CAfile = /etc/pki/tls/cert.pem
    smtp_tls_ciphers = medium
    smtp_tls_loglevel = 1
    smtp_tls_mandatory_protocols = !TLSv1, !SSLv2, !SSLv3
    smtp_tls_note_starttls_offer = yes
    smtp_tls_protocols = !SSLv2, !SSLv3
    smtp_tls_security_level = may
    smtpd_tls_CAfile = /etc/pki/tls/cert.pem
    smtpd_tls_auth_only = no
    smtpd_tls_cert_file = /etc/letsencrypt/live/my.example.com/fullchain.pem
    smtpd_tls_ciphers = medium
    smtpd_tls_dh1024_param_file = /etc/postfix/ssl/dh_2048.pem
    smtpd_tls_dh512_param_file = /etc/postfix/ssl/dh_512.pem
    smtpd_tls_eecdh_grade = strong
    smtpd_tls_exclude_ciphers = aNULL, eNULL, EX...