Category: Server Admin

Server Admin

Simple script to keep MySQL running

Post author By Jason
Post date July 1, 2017
No Comments on Simple script to keep MySQL running

Sometimes MySQL crash for various reasons (out of memory), there is a simple hack to make sure MySQL running.

Save this to dbcheck.sh

#!/bin/bash

PIDOF=/usr/sbin/pidof

SERVICE=/usr/sbin/service

if [[ ! `$PIDOF -s mysqld` ]]; then

$SERVICE mysqld restart # can be mysql or mariadb

echo "DB restarted"

else

echo "DB is healthy"

Make it executable by chmod +x dbcheck.sh , and setup a cronjob as root for it to run periodically (e.g. every minute)

1	* * * * * /home/jason/dbcheck.sh > /dev/null

Note that this is not considered a good practice, you should find out what is crashing the DB/service, but it is a simple hack to save your some time.

Use Slack as notification service in your workflow

Post author By Jason
Post date April 6, 2017
No Comments on Use Slack as notification service in your workflow

This article intend to give some pointers to developers new to Slack on how to integrate their services / workflow with it. You can add a message to Slack and get notified as simple as a command like this:

1	slack "Something is done"

My Use case

So my main purpose of using Slack it to get notified with certain events happen and implement it with minimum effort. For example,

Tags slack, workflow

Linux Server Admin

5 Docker tricks make your life easier – Part 1

Post author By Jason
Post date March 28, 2017
No Comments on 5 Docker tricks make your life easier – Part 1

1. Logs and monitoring

You can view logs of a container by

1	docker logs [container_name]

And you can monitor output from a container by

1	docker logs -f [container_name]

2. Open a shell in the container

If you want to quickly dive into the container,

Tags docker

Programming Server Admin Tech Tips and Tricks

Simple command to monitor directory changes on Mac

Post author By Jason
Post date October 31, 2016
No Comments on Simple command to monitor directory changes on Mac

Sometimes you want to know if a certain App/code/IDE changed something on the disk, this little script / command may come in handy.

Install fswatch

install fswatch as a global command

1	brew install fswatch

The script

Only fswatch is not enough, here is the script that does the trick

#!/bin/bash

fswatch -0 $@ | while read -d "" event; \

do \

echo ${event};

done

Save as a script e.g. monitor.sh, then give it executable permission

1	chmod +x monitor.sh

Now run the script and supply the path as parameter, and you will start monitoring the directory

1	./monitor.sh path/to/direcory

Enjoy!

OSX Programming Server Admin

Migrating to “Docker for Mac” from Toolbox

Post author By Jason
Post date June 30, 2016
No Comments on Migrating to “Docker for Mac” from Toolbox

As Docker for Mac becomes available, it’s about time to ditch Docker Toolbox which requires a VM running in background. The migration is surprisingly easy. The Official doc recommend you to read this article “Docker for Mac vs. Docker Toolbox“, while I think it’s a pretty good read, I will simply tell you the steps to migrate if you just need the info.

Linux Server Admin

Docker commands to clean unused images

Post author By Jason
Post date March 29, 2016
No Comments on Docker commands to clean unused images

If you use docker for some time, there will be a lot of trash images, volumes that is not used by any containers. Here’s how to remove them. (warning: not reversible)

Remove dangling images

1	docker rmi $(docker images -qf dangling=true)

Remove dangling volumes

1	docker volume rm $(docker volume ls -qf dangling=true)

As seen from above commands, you may guess the nested command within the $(…) is used to list dangling images/volumes

List dangling images

1	docker images -f dangling=true

List dangling volumes

1	docker volume ls -f dangling=true

Linux Server Admin

Using Dotenv config in Makefile (or anything)

Post author By Jason
Post date March 12, 2016
No Comments on Using Dotenv config in Makefile (or anything)

Ever want to use .env file config directly in Makefile? I found it not as easy as it sounds. I found this shell command on the web

Linux Server Admin Web Technology

Make Docker work with iptables

Post author By Jason
Post date March 8, 2016
No Comments on Make Docker work with iptables

Docker containers are just like a computer, the networking between host and containers is affected by the firewall. My iptables has a default DROP all policy, but it will make the Containers cannot communicate with the host. Here is the fix you’ll need.

Linux Programming Server Admin Web Technology

Docker named volume explained

Post author By Jason
Post date March 4, 2016
3 Comments on Docker named volume explained

Named volume is a new feature since Docker 1.9, it allows you to manage persistent data more easily, and also the volume can be provided by other storage drivers such as Glusterfs instead of “just a directory on the host”. This new feature is particularly useful in production environment. (On the Dev side, I think we still need mounted volume)

Tags docker

Linux Server Admin

Install Jetty as a service on CentOS

Post author By Jason
Post date June 30, 2015
1 Comment on Install Jetty as a service on CentOS

It seems hard to find a complete step-by-step tutorial to install Jetty as a service (especially on CentOS), some of the tutorial online is somewhat outdated or does not work, so I will share what I’ve learnt. (painfully) Perhaps this tutorial will also be outdated at some point in the future, so I will state the current version of the software I use clearly.