Setup of multilingual input for the Debian system is simplified by using the IBus family of packages with the im-config package. The list of IBus packages are the following.

The kinput2 method and other locale dependent Asian classic input methods still exist but are not recommended for the modern UTF-8 X environment. The SCIM and uim tool chains are an slightly older approach for the international input method for the modern UTF-8 X environment.

I find the Japanese input method started under English environment ("en_US.UTF-8") very useful. Here is how I did this with IBus.

Please note the following.

If you wish to input without going through XIM, set "$XMODIFIERS" value to "none" while starting a program. This may be the case if you use Japanese input infrastructure egg on emacs(1). From shell, execute as the following.

$ XMODIFIERS=none emacs

In order to adjust the command executed by the Debian menu, place customized configuration in "/etc/menu/" following method described in "/usr/share/doc/menu/html".

The environment variable "LANG=xx_YY.ZZZZ" sets the locale to language code "xx", country code "yy", and encoding "ZZZZ" (see Section 1.5.2, “"$LANG" variable”).

Current Debian system normally sets the locale as "LANG=xx_YY.UTF-8". This uses the UTF-8 encoding with the Unicode character set. This UTF-8 encoding system is a multibyte code system and uses code points smartly. The ASCII data, which consist only with 7-bit range codes, are always valid UTF-8 data consisting only with 1 byte per character.

Previous Debian system used to set the locale as "LANG=C" or "LANG=xx_YY" (without ".UTF-8").

Actual traditional encoding system used for "LANG=xx_YY" can be identified by checking "/usr/share/i18n/SUPPORTED". For example, "en_US" uses "ISO-8859-1" encoding and "fr_FR@euro" uses "ISO-8859-15" encoding.

The UTF-8 encoding is the modern and sensible text encoding system for I18N and enables to represent Unicode characters, i.e., practically all characters known to human. UTF stands for Unicode Transformation Format (UTF) schemes.

I recommend to use UTF-8 locale for your desktop, e.g., "LANG=en_US.UTF-8". The first part of the locale determines messages presented by applications. For example, gedit(1) (text editor for the GNOME Desktop) under "LANG=fr_FR.UTF-8" locale can display and edit Chinese character text data while presenting menus in French, as long as required fonts and input methods are installed.

I also recommend to set the locale only using the "$LANG" environment variable. I do not see much benefit of setting a complicated combination of "LC_*" variables (see locale(1)) under UTF-8 locale.

Even plain English text may contain non-ASCII characters, e.g. left and right quotation marks are not available in ASCII.

“double quoted text”
‘single quoted text’

When ASCII plain text data is converted to UTF-8 one, it has exactly the same content and size as the original ASCII one. So you loose nothing by deploying UTF-8 locale.

Some programs consume more memory after supporting I18N. This is because they are coded to use UTF-32(UCS4) internally to support Unicode for speed optimization and consume 4 bytes per each ASCII character data independent of locale selected. Again, you loose nothing by deploying UTF-8 locale.

The vendor specific old non-UTF-8 encoding systems tend to have minor but annoying differences on some characters such as graphic ones for many countries. The deployment of the UTF-8 system by the modern OSs practically solved these conflicting encoding issues.

In order for the system to access a particular locale, the locale data must be compiled from the locale database. (The Debian system does not come with all available locales pre-compiled unless you installed the locales-all package.) The full list of supported locales available for compiling are listed in "/usr/share/i18n/SUPPORTED". This lists all the proper locale names. The following lists all the available UTF-8 locales already compiled to the binary form.

$ locale -a | grep utf8

The following command execution reconfigures the locales package.

# dpkg-reconfigure locales

This process involves 3 steps.

The list of available locale should include "en_US.UTF-8" and all the interesting languages with "UTF-8".

The recommended default locale is "en_US.UTF-8" for US English. For other languages, please make sure to chose locale with "UTF-8". Any one of these settings can handle any international characters.

The value of the "$LANG" environment variable is set and changed by many applications.

You can chose specific locale only under X Window irrespective of your system wide default locale using PAM customization (see Section 4.5, “PAM and NSS”) as follows.

This environment should provide you with your best desktop experience with stability. You have access to the functioning character terminal with readable messages even when the X Window System is not working. This becomes essential for languages which use non-roman characters such as Chinese, Japanese, and Korean.

The following line defines file location of the language environment in the PAM configuration file, such as "/etc/pam.d/gdm3.

auth    required        pam_env.so read_env=1 envfile=/etc/default/locale

Change this to the following.

auth    required        pam_env.so read_env=1 envfile=/etc/default/locale-x

For Japanese, create a "/etc/defaults/locale-x" file with "-rw-r--r-- 1 root root" permission containing the following.

LANG="ja_JP.UTF-8"

Keep the default "/etc/defaults/locale" file for other programs as the the following.

LANG="en_US.UTF-8"

This is the most generic technique to customize locale and makes the menu selection dialog of gdm3(1) itself to be localized.

Alternatively for this case, you may simply change locale using the "~/.xsessionrc" file.

For cross platform data exchanges (see Section 10.1.10, “Removable storage device”), you may need to mount some filesystem with particular encodings. For example, mount(8) for vfat filesystem assumes CP437 if used without option. You need to provide explicit mount option to use UTF-8 or CP932 for filenames.

Samba uses Unicode for newer clients (Windows NT, 200x, XP) but uses CP850 for older clients (DOS and Windows 9x/Me) as default. This default for older clients can be changed using "dos charset" in the "/etc/samba/smb.conf" file, e.g., to CP932 for Japanese.

Translations exist for many of the text messages and documents that are displayed in the Debian system, such as error messages, standard program output, menus, and manual pages. GNU gettext(1) command tool chain is used as the backend tool for most translation activities.

aptitude(8) lists under "Tasks" → "Localization" provide extensive list of useful binary packages which add localized messages to applications and provide translated documentation.

For example, you can obtain the localized message for manpage by installing the manpages-<LANG> package. To read the Italian-language manpage for <programname> from "/usr/share/man/it/", execute as the following.

LANG=it_IT.UTF-8 man <programname>

The sort order of characters with sort(1) is affected by the language choice of the locale. Spanish and English locale sort differently.

The date format of ls(1) is affected by the locale. The date format of "LANG=C ls -l" and "LANG=en_US.UTF-8" are different (see Section 9.2.5, “Customized display of time and date”).

Number punctuation are different for locales. For example, in English locale, one thousand one point one is displayed as "1,000.1" while in German locale, it is displayed as "1.000,1". You may see this difference in spreadsheet program.