Tech

I have been using Docker and Kubernetes for several years now but never really took any time to really read about it. There were a lot of gaps in my understanding of how Docker works and what really is possible with it. Just recently my employer started to offer a Udemy subscription, so I took the Hands on Docker course. Here are some of the important things I learned in this course. ...

I was using mcrypt to encrypt json_encoded data. On the other side, mcrypt was able to decrypt data but json_decode was not working. It would throw JSON\_ERROR\_CTRL_CHAR error. However, without mcrypt, json_decode worked flawlessly. After some trial and error, I found that applying trim function after decrypting data would let me use json_decode without any issues.

I usually run it from under a partition which is running out of space. It can take a while. du -g | sort -n -r

Playing with Cordova, I was getting this error when building iOS version: Error: xcode-select: error: tool 'xcodebuild' requires Xcode, but active developer directory is a command line tools instance Even full install of Xcode didn’t fix this error. The solution was to run the following command to use full Xcode instead of command line tools version that I had installed earlier: sudo xcode-select --switch /Applications/Xcode-beta.app/Contents/Developer

I followed instructions here: https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-postfix-as-a-send-only-smtp-server-on-ubuntu-18-04 Everything seemed okay but emails were not getting delivered. Logs showed me that smtp connections were timing out: tail -f /var/log/mail.log May 3 12:28:10 postfix/smtp[3160]: connect to gmail-smtp-in.l.google.com[172.217.197.27]:25: Connection timed out May 3 12:28:10 postfix/smtp[3160]: connect to alt1.gmail-smtp-in.l.google.com[2800:3f0:4003:c00::1a]:25: Network is unreachable May 3 12:28:40 postfix/smtp[3160]: 4984C41A1E: to=<xxxx@gmail.com>, relay=none, delay=3246, delays=3186/0.01/60/0, dsn=4.4.1, status=deferred (connect to alt2.gmail-smtp-in.l.google.com[2a00:1450:400b:c00::1a]:25: Network is unreachable) However, I could ping any of the above ip addresses just fine. ...

Put enctype="multipart/form-data" in your form tag.

Without full understanding, I had enabled HSTS on amerkhalid.com with option includeSubDomains. I had a subdomain that was used as “Custom Domain” to SmugMug site. After enabling HSTS, these subdomains started to throw NET::ERR_CERT_COMMON_NAME_INVALID. The fix is of course simple, don’t use includeSubDomains. But that opens up your top level domain to man in the middle attacks. For now, I decided to follow the best practices and leave includeSubDomains enabled. And decided to not use a custom domain for my SmugMug site. ...

While playing with https://github.com/alexa/interactive-adventure-game-tool, I ran into the following error: > interactive-adventure-game-tool@1.0.0 start /Users/amer/alexa/interactive-adventure-game-tool > node node_modules/gulp/bin/gulp.js /Users/amer/alexa/interactive-adventure-game-tool/node_modules/require-dir/index.js:97 if (!require.extensions.hasOwnProperty(ext)) { ^ TypeError: require.extensions.hasOwnProperty is not a function at requireDir (/Users/amer/alexa/interactive-adventure-game-tool/node_modules/require-dir/index.js:97:37) at Object.<anonymous> (/Users/amer/alexa/interactive-adventure-game-tool/gulpfile.js:1:85) at Module._compile (module.js:660:30) at Object.Module._extensions..js (module.js:671:10) at Module.load (module.js:573:32) at tryModuleLoad (module.js:513:12) at Function.Module._load (module.js:505:3) at Module.require (module.js:604:17) at require (internal/module.js:11:18) at Liftoff.handleArguments (/Users/amer/alexa/interactive-adventure-game-tool/node_modules/gulp/bin/gulp.js:116:3) npm ERR! code ELIFECYCLE npm ERR! errno 1 npm ERR! interactive-adventure-game-tool@1.0.0 start: `node node_modules/gulp/bin/gulp.js` npm ERR! Exit status 1 npm ERR! npm ERR! Failed at the interactive-adventure-game-tool@1.0.0 start script. npm ERR! This is probably not a problem with npm. There is likely additional logging output above. npm ERR! A complete log of this run can be found in: npm ERR! /Users/amer/.npm/_logs/2018-01-02T05_12_24_832Z-debug.log The solution was to update require-dir to version 0.3.2 in package.json and run npm install again. ...

echo 1 >/proc/sys/net/ipv4/icmp_echo_ignore_all

Setting up Ingress is an easy process but when it doesn’t work it gets really painful. First, make sure you have Ingress Controller setup correctly. This is in addition to Ingress resource and should be automatically setup by your cloud provider. When I was trying to setup a Kubernetes cluster on IBM Cloud, I ran into a lot of issues. It seems due to my permissions level something went wrong during provisioning of Kubernetes and Ingress Controller was not setup correctly. I went through a lot of steps including recreating alb , ingress resources, etc. The final fix was to login to IBM Cloud as superuser to change Access Policies for the cluster. Once I did that, everything just worked magically. ...