... shutdown a system at specific time

I need to shutdown a server at a specific hour a few days from now.  The command shutdown allows to specify the hour but the day so that can't be used.  It also allows to specify a number of minutes from "now" which implies computing that value.  So the following can be used:

sudo shutdown -h +$(($(($(date -d 'yyyy-mm-dd hh:mm:ss' +"%s") - $(date +"%s"))) / 60))

There is also the at command but I'm sure how that well that work with commands that would require sudo.

... install bioformats in Debian and Ubuntu

Bioformats is not packaged in Debian and therefore, not in Ubuntu either. To install it in a way that will make it play best with the rest of the system, following the expected standards, use the following (adjusting the download URL for the bioformats version you want):

 sudo mkdir /usr/local/share/java/  
 sudo wget http://downloads.openmicroscopy.org/bio-formats/5.1.3/artifacts/bioformats_package.jar \  
  -O /usr/local/share/java/bioformats_package-5.1.3.jar  
 sudo ln -s bioformats_package-5.1.3.jar /usr/local/share/java/bioformats_package.jar  

This mimics how java packages are installed by Debian.  The actual jar has the version on the filename, while the unversioned filename is a symbolic link to a specific version.  This allows you to have multiple versions installed while keeping one (usually the latest) as the default.

apt would install those files in /usr/share/java so we place them in /usr/local/share/java instead. Remember that the whole /usr hierarchy should be considered off-limits, only the package manager should change things there.  The exception is /usr/local.  You can think of /usr/local being the equivalent as /usr that is managed by the system administrator instead of the package manager.  From the Linux Filesystem Hierarchy Standard:

The /usr/local hierarchy is for use by the system administrator when installing software locally.
[...]
Locally installed software must be placed within /usr/local rather than /usr unless it is being installed to replace or upgrade software in /usr.

... not download translations files in Debian

Updating the APT's package cache on the testing version of Debian (Wheezy) will show a lot of hits, related to translations. A bunch of the following.

...
Hit http://ftp.ie.debian.org wheezy/main Translation-hu
Hit http://ftp.ie.debian.org wheezy/main Translation-fr
Hit http://ftp.ie.debian.org wheezy/main Translation-vi
Hit http://ftp.ie.debian.org wheezy/main Translation-zh
Hit http://ftp.ie.debian.org wheezy/main Translation-ru
...

The quick answer

Run the commands

$ sudo rm /var/lib/apt/lists/*_i18n_Translation*
$ echo 'Acquire::Languages "environment";' | sudo tee -a /etc/apt/apt.conf.d/99translations

This assumes that downloaded package lists are placed at /var/lib/apt/lists/. It is unlikely this default was changed but if these two commands did not work, read the very long answer below.

The wrong way

Do not set up the Languages option to "none", you will lose the long description for all package in all languages, including English.

Do not edit the apt.conf.d/70debconf file or create an apt.conf file. this has been modularized. The idea is that by having multiple files, it's easier to maintain and write scripts that will change the settings.

The right way (long answer)

These translations are the descriptions of packages in the APT cache (what the guys from the Debian Description Translation Project do), and not related to the actual translations of whatever packages you decide to install. The files being downloaded are the long descriptions^[1] for all languages, and the short descriptions for all non-English languages.

These files will be located at /var/lib/apt/lists/ ^[2] and have the word Translation on their name. Note that the English language is also considered a translation (the file that ends in i18n_Translation-en).

Downloading all this languages files takes up a lot of time (there's a lot of small files which maybe comes from Debian Wheezy still being in testing and will reduce once it goes stable) and extra space on the disk (120MB at the moment).

Reading the man page of apt.conf shows a Language option to select which translation files should be downloaded^[3]. This option should be set to "environment". Most advice out there is to set this option to "none". This will cause no translation to be downloaded at all, including your own language, even if it is English. Setting this to "none", really means no package description at all (except the short descriptions in English).

The option "environment" is translated into the LC_MESSAGES environment variable. These variables are not actually exported but their value can be inspected with the locale program (run sudo dpkg-reconfigure locales to change locales).

## display locale variables
$ locale
LANG=en_IE.utf8
LANGUAGE=
LC_CTYPE="en_IE.utf8"
LC_NUMERIC="en_IE.utf8"
LC_TIME="en_IE.utf8"
LC_COLLATE="en_IE.utf8"
LC_MONETARY="en_IE.utf8"
LC_MESSAGES="en_IE.utf8"
LC_PAPER="en_IE.utf8"
LC_NAME="en_IE.utf8"
LC_ADDRESS="en_IE.utf8"
LC_TELEPHONE="en_IE.utf8"
LC_MEASUREMENT="en_IE.utf8"
LC_IDENTIFICATION="en_IE.utf8"
LC_ALL=

## show available locales
$ locale -a
C
C.UTF-8
en_GB.utf8
en_IE.utf8
en_US.utf8
POSIX
pt_PT.utf8

Back to the translation, this is done in the files of /etc/apt/apt.conf.d, the collection of which makes the configuration of APT. Each of these files have the format of a two digit number (the order in which they are read) followed by a word (a reference to what they do).

$ ls /etc/apt/apt.conf.d/
00aptitude      01autoremove   20packagekit
00CDMountPoint  20dbus         50unattended-upgrades
00trustcdrom    20listchanges  70debconf

The numbers make it easier to know which files are read first, thus avoiding problems by having opposite settings in different files and not knowing which setting is in effect. In case of opposite settings, it's the last one that counts.

These files are generated automatically by Debian and you shouldn't edit them directly. You never know when an update, or installing a new package may change something. But Debian will not touch files you created. The rule is, edit only your own files and leave to Debian, the files that Debian creates.

So create a new file, with the number 99 (so that you know this setting is loaded last) and give it some meaningful name. A file named 99translations would be appropriate. The following command will create the file with the correct line (and in the case it already exists, will append to it so make sure what you have in the end).

$ echo 'Acquire::Languages "environment";' | sudo tee -a /etc/apt/apt.conf.d/99translations

If later you wish to change some other setting, there is no problem in using the 99 number again. For example, there is no problem is using a 99proxies file (maybe to specify special proxies that should be used to download packages) together with a 99translations file.

When updating the package index, translations files found will also be updated, even if not listed in the locales or the Language options. So it is necessary to remove those files (also to retrieve the disk space). It is safe to remove all of them, they will be downloaded again once aptitude update is ran.

$ sudo rm /var/lib/apt/lists/*_i18n_Translation*

Note the the path for this files is configurable and they may be located somewhere else.^[2]

Footnotes:

[1] There are two types of description in a package. The short, 1 line description (that is displayed with aptitude search) and a longer one (that is added to it when using aptitude show). Compare the following two for the scons package:

• short description: replacement for make
• long description: SCons is a make replacement providing a range of enhanced features such as automated dependency generation and built in compilation cache support.  SCons rule sets are Python scripts so as well as the features it provides itself SCons allows you to use the full power of Python to control compilation

[2] The translation files (downloaded from locations listed in sources.list), are by default saved in /var/lib/apt/lists but this is actually configurable. The path used is set with the option Dir::State::Lists. Use apt-config dump to inspect their values:

$ apt-config dump

 ... 
Dir "/";
Dir::State "var/lib/apt/";
Dir::State::lists "lists/";
 ... 

 [3] apt.conf (5) manual page, section "The acquire group", subsection "Languages":

The Languages subsection controls which Translation files are downloaded and in which order APT tries to display the description-translations. APT will try to display the first available description in the language which is listed first. Languages can be defined with their short or long language codes. Note that not all archives provide Translation files for every language - the long language codes are especially rare.

The default list includes "environment" and "en". "environment" has a special meaning here: it will be replaced at runtime with the language codes extracted from the LC_MESSAGES environment variable. It will also ensure that these codes are not included twice in the list. If LC_MESSAGES is set to "C" only the Translation-en file (if available) will be used. To force APT to use no Translation file use the setting Acquire::Languages=none. "none" is another special meaning code which will stop the search for a suitable Translation file. This tells APT to download these translations too, without actually using them unless the environment specifies the languages. So the following example configuration will result in the order "en, de" in an English locale or "de, en" in a German one. Note that "fr" is downloaded, but not used unless APT is used in a French locale (where the order would be "fr, de, en").

    Acquire::Languages { "environment"; "de"; "en"; "none"; "fr"; };

Note: To prevent problems resulting from APT being executed in different environments (e.g. by different users or by other programs) all Translation files which are found in /var/lib/apt/lists/ will be added to the end of the list (after an implicit "none").