## Handy Docker Tools

As I’m working with Docker quite intensively it was about time to develop some tools that help me managing different tasks. Some of them have already been existing as functions in my environment or something, but now they are assembled in a git repository at GitHub.

The toolbox currently consists of the following tools:.

## dclean cleans your setup

The Docker-Clean tool dclean helps getting rid of old, exited Docker containers. Sometimes I forget the --rm flag during tests, and when I realise it there are already hundreds of orhpaned containers hanging around.. Running dclean without arguments removes all of them quickly.

Additionally, the dclean tool accepts a -i flag which will clean the images. It will prune all dangling images. Dangling images are orphaned and usually not needed anymore. Thus, dclean -i will remove them.

## denter gets you into a containers

The Docker-Enter tool denter beames you into a running Docker container. Just provide the container’s name or CID as an argument to get a /bin/bash inside the container. Internally, denter will just call

with $EXEC being /bin/bash by default. So there is no magic, it’s just a shortcut.. You may overwrite the program to be executed by providing it as a second argument. That means, will execute ps -ef in the container with the id SOMEID. ## dip shows IP addresses The Docker-IP tool dip shows the IP addresses of running containers. Without arguments it will print the IP addresses, names, and container ids of all running containers. If your interested in the IP address of a specific container you may pass that container’s CID as an argument with -c, just like: This will show the IP of the container with id SOMEID. ## dkill stops all running containers The Docker-Kill tool dkill is able to kill all running containers. It doesn’t care what’s in the container, it will just iterate over the docker ps list to stop all running containers. As this is quite dangerous, it requires a -f flag to actually kill the containers. You may afterwards run the dclean tool from above to get rid of the cadavers.. ## dupdate updates images The Docker-Update tool dupdate helps you staying up-to-date. It will iterate over all your images and tries to pull new versions of that image from the Docker registry (or your own registry, if you have one). By default, it will echo the images that have been updates and tells you which images cannot be found (anymore) on the registry. You may pass the -v to dupdate to enable verbose mode and also get a report for images that do not have a newer version at the registry. This way, you can make sure that all images are checked. Similarly, you can pass -s to enable silent mode and suppress messages about images that cannot be found at the registry. You may also want to look at the Docker-Update tool? # Installation Installing the tools is very easy: Just clone the Docker-Tools git repository at GitHub. If you’re using a Debian based system you may also install the tools through my apt-repository: This way, you’ll stay up-to-date with bug fixes etc. ## Firefox: Mute Media You middle-click a few youtube videos and all start shouting against each other. You enter a website and it immediately slaps sound in you face. How annoying… But there may be help. Enter about:config and set • media.block-play-until-visible to true to only play media that is also in the current tab an do not play the stuff from the background • media.autoplay.enabled to false to stop autoplaying of some of the media (doens’t work everywhere, not sure why..) • dom.audiochannel.mutedByDefault sets the audio muted by default – essential for offices • plugins.click_to_play requires a click to run plugins, such as flash (which you are anyway not using!) ## Fix highlight colors for QT apps on a GTK desktop I’m using the i3 window manger. As smart as possible, increases productivity, and feels clean. Exactly how I like my desktop. I’m still very happy that Uschy hinted me towards i3! However, I’m experiencing a problem with highlighted text in Okular, my preferred PDF viewer. When I highlight something in Okular the highlight-color (blue) is far too dark, the highlighted text isn’t readable anymore. I used to live with that, but it was quite annoying. Especially when you’re in a meeting/presentation and you want to highlight something at the projector. I just saw that problem occurring in Okular. Not sure why, but I honestly do not understand this whole desktop config thing – probably one of the reasons why I love i3 ;-) Today, I eventually digged into the issue and found out what’s the problem how to solve the problem. Apparently, Okular uses a Qt configuration, that can be modified using the qtconfig tool. Just install it (here for Qt4 applications): When you run qt4-qtconfig a window will pop up, as you can see in the figure on the right: 1. Select a GUI Style that is not Desktop Settings (Default), e.g. Cleanlooks. 2. Then you can click the Tune Palette… button in the Build Palette section. 3. A second window will pop up. Select Highlight in the Central color roles section. 4. Finally you’re good to select the hightlight color using the color chooser button! :) Was a bit difficult to find, but the result is worth it! The figure on the bottom shows the new highlight color – much better. I will probably never understand all these KDE, QT, Gnome, GTK, blah settings. Every environment does it differently and changes the configuration format and location like every few months. At least for me that’s quite frustrating… ## Mail support for Docker's php:fpm Dockerizing everything is fun and gives rise to sooo many ideas and opportunities. However, sometimes it’s also annoying as …. For example, I just tried to use a Docker container for a PHP application that sends emails. Usually, if your server is configured ok-ish, it works out of the box and I never had problems with something like that. ## The Issue In times of Docker there is just one application per container. That means the PHP container doesn’t know anything about emailing. Even worse, the configuration tool that comes with PHP tries configuring the sendmail_path to something like $SENDMAILBINARY -t -i. That obviously fails, because there is no sendmail binary and \$SENDMAILBINARY remains empty, thus the actual setting becomes:

That, in turn, leads to absurd messages in your log files, because there is no such binary as -t:

WARNING: [pool www] child 7 said into stderr: "sh: 1: -t: not found"


Hard times to start debugging that issue..

## The Solution

To solve this problem I forked the php:fpm image to install sSMTP, a very simple MTA that is able to deliver mail to a mail hub. Afterwards I needed to configure the sSMTP as well as the PHP mail setup.

### Install sSMTP into php:fpm

Nothing easier than that, just create a Dockerfile based on php:fpm and install sSMTP through apt:

Docker-build that image either through command line or using Docker Compose or whatever is your workflow. For this example, let’s call this image binfalse/php-fpm-extended.

### Setup for the sSMTP

PLEASE NOTE: sSMTP is not maintained anymore! Please switch to msmtp, for example, as I explained in Migrating from sSMTP to msmtp.

Configuring the sSMTP is easy. Basically, all you need to do is to specify the address to the mail hub using the mailhub option. However, as my mail server is running on a different physical server I also want to enable encryption, so I set UseTLS and UseSTARTTLS to YES. Docker containers usually get cryptic names, so I reset the hostname using the hostname variable. And last but not least I allowed the applications to overwrite of the From field in emails using the FromLineOverride. Finally, your full configuration may look like:

Just store that in a file, e.g. /path/to/ssmtp.conf. We’ll mount that into the container later on.

### Configure mail for php:fpm

PLEASE NOTE: sSMTP is not maintained anymore! Please switch to msmtp, for example, as I explained in Migrating from sSMTP to msmtp.

Even if we installed the sSMTP the PHP configuration is still invalid, we need to set the sendmail_path correctly. That’s actually super easy, just create a file containing the following lines:

Save it as /path/to/php-mail.conf to mount it into the container later on.

### Putting it all together

To run it, you would need to mount the following things:

• /path/to/php-mail.conf to /usr/local/etc/php/conf.d/mail.ini
• /path/to/ssmtp.conf to /etc/ssmtp/ssmtp.conf
• your PHP scripts to wherever your sources are expected..

Thus a Docker Compose configuration may look like:

Give it a try and let me know if that doesn’t work!

Docker resources:

Some sSMTP resources that helped me configuring things:

## Thunderbird opens multiple windows on startup

Since some time my Icedove/Thunderbird (currently version 38.8.0) uses to open two main windows when I launch it. That’s a bit annoying, as there are always two windows visually trying to catch my attention. Even if I read the new mail in one of them the other one would still demand attention.

That’s of course a bit annoying. The preferences dialog doesn’t seem to offer a button for that. I’ve been looking for a solution on the internet, but wasn’t able to find something. And unfortunately, there is an easy workaround: Just close the second window after startup… The other window will appear again with the next start of Icedove/Thunderbird, but that’s the problem of future-me. These nasty easy workarounds! You won’t fix the problem and it tends to bug you a little harder with every appearance.

Today I had some time to look into the issue.

I sensed the problem in my Thunderbird settings - if that would be an actual Thunderbird issue I would have found something on the internet.. Thus, it must be in my ~/.icedove/XXXX.default directory. Studying the prefs.js file was quite interesting, but didn’t reveal anything useful for the current issue. Then I spotted a session.json file, and it turns out that this caused the problem! It contained these lines: cat session.json | json_pp

(For brevity I replaced my actual main tab’s content with ....)

As you see, there is JSON object containing a single key windows with an array of two objects. These two objects apparently represent my two windows. Both have tabs. For example in the second window object my calendar and my tasks are opened in tabs (that’s the lightning/iceowl extension), and a single message occupies another tab.

Brave as I am I just deleted the first window object (I decided for the first one as that had no extra tabs). And voilà! The next launch of Thunderbird just opens a single window! :)

I don’t know who wrote the stuff into the session.json, it was probably caused by one of my extensions. However, it seems to be stable now. And if it ever happens again I’ll know how to fix it.

Easy solution, should have fixed that immediately!

## Update

I found out what caused the problem: It is FireTray – an extension that I’m using to have a systray notification icon. This extension sits in the systray and changes its icon when a new mail arrives. That’s super useful, but… by default it doesn’t close windows but just hides them to systray! That means you can restore them in the context menu of the systray icon… And that means that the windows aren’t really closed and will appear again with the next start of the application.

To change that behaviour just right-click the icon and click Preferences. A dialog window will pop up and you just need to unselect the Closing window hides to systray. Compare the screenshot. You may also go for Only last window can be hidden.