DevOps Resources on sk33lz

Helpful DNS Information

Sun, 05 May 2019 00:00:00 +0100

DNS, or Domain Name System, is one of the most important components of the Internet. It is the service of the web that converts an IP address to a hostname, allowing websites to have their easy to remember names like sk33lz.com. Without it, you would need to remember IP addresses for websites like you used to have to remember someone’s phone number. Thanks to smartphones we don’t need to do that anymore either.

The IPs used in the examples below are the actual IPv4 and IPv6 IPs of this website’s server.

IPv4 DNS Records

A Name Record

The A Name Record is probably the most common DNS record, as it is used to assign the TLD, Top Level Domain, and subdomains to an IPv4 IP address.

Examples

Primary Domain

The following entry can be set for the A Record on your primary domain name.

@ 10.10.10.10

Subdomain Domain

The following entry can be set for the A Record on your www subdomain.

www 10.10.10.10

Parts of the web are also evolving. Did you know we ran out of IPv4, 32-bit, IP addresses last year? Those are the ones that look like 123.123.123.123. The last free IP address block for IPv4 was depleted on September 24, 2015. That was a total of 4,294,967,296 IPs, 588,514,304 of which are reserved IPs, so we have gone through a total of 3,706,452,992 IPs since the inception of the Internet. This means that soon enough there will be no IPv4 IPs to assign to computers and devices around the world. Luckily, we have IPv6, a 64-bit IP address range, that has the possibility of theoretically allowing up to 340,282,366,920,938,463,463,374,607,431,768,211,456 IPs. It should be a while before we hit that theoretical maximum, so let’s see what we need to do to get ready for this changeover in terms of DNS.

IPv6 DNS Records

These DNS entries are specific to IPv6, or combined with IPv4 and IPv6.

AAAA Name Record

The AAAA Name Record is similar to an A Name Record, but maps an IPv6 IP address to a hostname instead. Typically you will assign this to @ or hostname of the A Name Record that corresponds to the IPv4 IP.

Examples

Primary Domain

The following entry can be set as the AAAA or IP6 record for your primary domain name.

@ 0:0:0:0:0:ffff:a0a:a0a

Subdomain Domain

The following entry can be set as the AAAA or IP6 record for your www subdomain.

www 0:0:0:0:0:ffff:a0a:a0a

IPv4 and IPv6 Combined SPF Record

Google recently started requiring SPF records to be assigned to mail server transactions on Gmail’s servers. This requires a specific TXT record in your DNS. Typically you would assign to @ or the A Name Record and AAAA Name Record you have assigned to the IPv4 and IPv6 IPs respectively.

@ v=spf1 a mx ip4:10.10.10.10 ip6:0:0:0:0:0:ffff:a0a:a0a ~all

Subdomain Domain

The following entry can be set as the AAAA or IP6 record for your www subdomain.

www v=spf1 a mx ip4:10.10.10.10 ip6:0:0:0:0:0:ffff:a0a:a0a ~all

DNS Tools

Ubuntu Linux Troubleshooting

Sun, 05 May 2019 00:00:00 +0100

Over the years I have ran into some odd issues setting up Ubuntu servers. I currently am running an Ubuntu 12.04.5 LTS and an Ubuntu 14.04.1 LTS server. Below you can find some helpful fixes for some Ubuntu bugs and configuration oddities.

Encrypted Home Directory

I ran into an issue installing an Ubuntu 14.04.1 LTS server where after installation I was unable to connect to my server through SSH using SSH key authentication and no password authentication. Everything seemed to work, but when I moved my server down to my basement for the summer, I was unable to connect through SSH remotely. I found that I could login if I were to login on the server console. After some searching I found that an authorized_keys file in an Ubuntu Encrypted Home Directory will not work properly. To fix this issue, you have to move the authorized keys file outside of your Encrypted Home Directory. Then modify the following line in your /etc/ssh/sshd_config file to point to the unencrypted location.

AuthorizedKeysFile %h/.ssh/authorized_keys

Web Performance

Sun, 05 May 2019 00:00:00 +0100

Performance has become a major factor of web development and application development for the modern web. According to Google, their search index algorithms use page load times as one of over 100 factors they use to rank their search engine results. Web developers that have already been focusing on server performance and faster page load times have the early advantage.

I work on optimizing web server performance and optimizing website performance as one of my responsibilities as the Systems Engineer at Zivtech in Center City, Philadelphia. Many of the tools I use are open source and free to use, but some might not be as easy to use as others. This section of my DevOps Resources will be focusing on how you can optimize your website for performance and if needed optimize your web server performance to help speed up your website.

Web Security

Sun, 05 May 2019 00:00:00 +0100

Security is a big part of my job as a web developer and server administrator. There are constantly new security issues being found in all facets of computers, whether it be your desktop operating system, your network, or a server operating system. This section of my site will be focused on helping you secure your network, your server, and/or desktop to reduce the chances of you becoming a victim of a hacker, a virus, or malware. Knowing how to find security updates quickly as they are released, or installing them automatically is key to staying secure in today’s web.