All posts by Max Chinni

Cache deb packages with apt-cacher-ng

How to, Linux, , , , , , , , ,
I’m playing with Docker and I’m constantly tuning my Dockerfile to install the needed packages.

This continuous refinement forces the build process to download the same deb packages every time and it becomes an actual waste of time and bandwidth.

Solution

apt-cacher-ng is a service which can be run on a Debian or Ubuntu host and will serve as a local cache for deb packages from Debian or Ubuntu repositories.

That’s what I need because I’m on an Ubuntu machine emulating a Debian container.

Host setup

The setup is really easy:

# aptitude install apt-cacher-ng

After the installation I changed the bind address of the service to keep it local (I don’t need LAN exposure), I added my local proxy to reach the internet and I disabled ReuseConnections (see Problems):

root@yoda:/etc/apt-cacher-ng# diff acng.conf acng.conf.old 
28d27
< BindAddress: localhost 172.17.42.1
35d33
< proxy: http://127.0.0.1:5865
322d319
< ReuseConnections: 0

Client setup

On the client side it’s necessary to force apt requests to use the proxy.
In the Dockerfile I added

RUN echo 'Acquire::http::Proxy "http://172.17.42.1:3142";' > /etc/apt/apt.conf.d/90-apt-cacher.conf

which creates the configuration file read by apt-get or aptitude when downloading packages.

Problems

The apt-cacher-ng server seems buggy at least when used in conjunction with a regular proxy. Sometimes I get errors like these on the client side

Err http://http.debian.net/debian/ wheezy/main netbase all 5.0
500  Invalid header

one possible solution is to perform a

# apt-get update

on the host machine (it seems to help). Another useful setting is

ReuseConnections: 0

as explained before.

HP ProBook 4540s brightness control in Ubuntu 13.10

Hardware, How to, Linux, , , , ,
The HP ProBook 4540s is a good choice when you need a GNU/Linux machine, but there are some hit and miss on the details. The thing I found most tedious is the brightness controls using the keyboard: they simply don’t work at all.

My soloution

See the kernel parameters actually used:

$ cat /proc/cmdline 
BOOT_IMAGE=/boot/vmlinuz-3.11.0-15-generic root=UUID=8850c025-676a-4e8c-ac83-4ed1147b88d4 ro quiet splash vt.handoff=7

If there’s no reference to acpi_backlight, that’s the problem. Add the parameter to /etc/default/grub changing the following line from

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

to

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"

Done

Markdown Viewer Firefox Extension Screenshot

Markdown Viewer Firefox Extension

web, , ,
I’m spanning the use of Markdown in every place I can: project documentation, blogging, note taking etc.

A useful Firefox extension I found is Markdown Viewer. It let you view Markdown files, HTML formatted, directly in the browser window. It’s useful when you have md files on the local filesystem that you want to quickly preview.

Problem: Firefox tries to download every .md file

I found a really annoying problem using this extension and I’m going to describe how I solved it: let’s say I have a file called notes.md in my home directory (/home/max/notes.md), I should view that file in Firefox visiting the url file:///home/max/notes.md.
At this point Firefox wants to download it and there’s no easy way to force it to use the extension.

The solution is to edit a configuration file

$ vi ~/.mozilla/firefox/*.default*/mimeTypes.rdf

and add a text/plain dedicated area with the md extension specified:

<RDF:Description RDF:about="urn:mimetype:text/plain"
    NC:value="text/plain"
    NC:fileExtensions="md"
    NC:description="Text Document">
  <NC:handlerProp RDF:resource="urn:mimetype:handler:text/plain"/>
</RDF:Description>

The last thing is to restart Firefox and everything should now work.

My set up

Just a side note: I’m running Ubuntu 13.10 with Firefox 26.0 and Markdown Viewer 1.3.

References

The comments on the extension page.

Detect Markdown files in vim

Uncategorized,
Quick tip which force vim to recognize .md files as Markdown formatted files:

  • create, if not exists, the needed directory 
    mkdir -p ~/.vim/ftdetect/
  • create the file ~/.vim/ftdetect/markdown.vim with this content 
    autocmd BufNewFile,BufRead *.md,*.mkdn,*.markdown :set filetype=markdown

Done.

Markdown on Save

web, , , , ,

Markdown

If you don’t know what Markdown is, then you should. I suggest you to read the Wikipedia page which gives some historical intro, too.

Markdown on Save

“Markdown on Save” is a WordPress plugin which allows you to write articles in Markdown format and have them correctly displayed on your WordPress blog.

I’m actually testing this plugin now, with this article and I will tell you my personal experience.
I found some weird initial problems, but the plugin looks great and I think it will be my default choice from now on.

Problems

The plugin does not have a valid header

The first problem I had was at the end of the installation process: I received the message “The plugin does not have a valid header.” and so it was not activated.

The solution was simple: I went to Plugins, Installed plugins and clicked Activate under Markdown on Save section.

Done.

How do I use it?

Yes, there was some misleading factors which led me to loose some minutes tinkering what I’ve had to do:

  • the first time I opened the new post page, there wasn’t any indication of the plugin functionality
  • searching on web I found the WordPress.org official plugin page where the author talked about a box marked as “This post is formatted with Markdown” to click. I hadn’t it. Then I found it, it didn’t seem a checkbox so I got confused (and there wasn’t any describing text).
    the Markdown box
  • I’ve a personal css for <code> blocks which are rendered with display: block; style. This is not totally compatible with the style of this plugin HTML output, so I’ve tweaked a bit the source code to embed the Markdown HTML result in a special div to apply special formatting. Here’s my opinion on that: there’s no way to dynamically understand that a page was from Markdown source or from the WordPress standard compose method. Maybe this is a good choice, but it doesn’t fit my needs

Conclusions

Many thanks to the author of the plugin, it’s quite perfect.