107.3 Localisation and Internationalisation

Weight: 3

Goal: Configure the locale and time zone settings on a Linux system.

1. Two Related but Distinct Concepts

In practice, the exam is about three things you actually configure on a Linux system:

1. The time zone.
2. The locale (language, character encoding, formatting rules).
3. The character set (UTF-8 vs. older encodings).

2. Time Zone

The hardware clock vs. the system clock

A Linux machine has two clocks:

• Hardware (RTC) clock — kept by the motherboard battery. Read at boot.
• System clock — kept by the kernel while the system is running.

The hardware clock can be set to either UTC (recommended for Linux-only systems) or local time (common when dual-booting Windows). Linux always works internally in UTC and converts to local time using the time zone setting.

Time zone files

Setting the time zone

Method 1 — modern (systemd):

timedatectl list-timezones                  # browse available zones
timedatectl set-timezone Europe/Paris       # set the system time zone
timedatectl                                 # show current settings

Method 2 — manual (works everywhere):

ln -sf /usr/share/zoneinfo/Europe/Paris /etc/localtime
echo "Europe/Paris" > /etc/timezone         # Debian/Ubuntu

Method 3 — interactive (Debian/Ubuntu):

dpkg-reconfigure tzdata

The TZ environment variable

Setting TZ in a shell overrides the system time zone for that session only:

$ date
Mon May 11 14:00:00 CEST 2026
$ TZ=Asia/Tokyo date
Mon May 11 21:00:00 JST 2026
$ export TZ=UTC               # affects this shell from now on

Useful for scripts that need to print times in a specific zone without changing the whole system.

Time-related commands

3. Locale: Language and Regional Formatting

A locale controls how programs display dates, numbers, sort strings, what language they speak, and what character encoding they use.

Locale name format

language[_TERRITORY][.codeset][@modifier]

Examples:

Locale environment variables

A locale isn’t one setting — it’s a set of variables, one per category. You can set them all at once with LANG, override one or more with LC_*, or override everything with LC_ALL.

Precedence

LC_ALL    >    LC_*    >    LANG    >    "C"  (default if nothing set)

So if LC_ALL=C is set, all other settings are ignored.

The locale command

locale                  # show all current locale variables
locale -a               # list all locales installed on the system
locale -m               # list available character maps (UTF-8, ISO-8859-1, ...)
LANG=fr_FR.UTF-8 date   # run one command in a different locale

Configuration files

Generating and switching locales

# Debian / Ubuntu
sudo dpkg-reconfigure locales              # interactive menu
sudo locale-gen en_US.UTF-8 fr_FR.UTF-8    # generate listed locales
sudo update-locale LANG=fr_FR.UTF-8        # set system default

# Modern systemd
sudo localectl list-locales
sudo localectl set-locale LANG=fr_FR.UTF-8

# RHEL / Fedora — install the language pack first
sudo dnf install glibc-langpack-fr

4. Character Encoding

A character encoding maps numbers stored on disk to characters on screen.

Key encodings to know

UTF-8 is the modern default everywhere. New Linux systems use locales ending in .UTF-8.

Inspecting and converting files

file mydata.txt                   # guesses encoding
# mydata.txt: UTF-8 Unicode text

iconv -f ISO-8859-1 -t UTF-8 old.txt -o new.txt
# Convert a file from Latin-1 to UTF-8.

iconv -l                          # list all encodings iconv knows

iconv is the standard tool for converting between encodings.

5. Practical Scenarios

Force English output for predictable script parsing

Many sysadmin scripts begin with:

export LC_ALL=C

This makes date, grep, sort, etc. produce output in plain ASCII English, regardless of the user’s settings. Crucial when parsing command output.

Run one command in another language

$ LANG=de_DE.UTF-8 date
Mo 11 Mai 2026 14:00:00 CEST

Sort that ignores accents

$ LC_COLLATE=C sort file.txt        # strict byte order

The default locale’s sort order can group accented characters with their base letter — sometimes desirable, sometimes not.

6. Quick Reference for the Exam

Files and directories:

• /etc/timezone
• /etc/localtime
• /usr/share/zoneinfo/
• /etc/locale.conf (or /etc/default/locale on Debian)
• /etc/locale.gen

Environment variables:

• TZ
• LANG
• LC_ALL
• LC_* (CTYPE, COLLATE, TIME, NUMERIC, MONETARY, MESSAGES, …)

Commands:

• date
• hwclock
• timedatectl
• tzselect, tzconfig (older interactive tools)
• locale
• localectl
• locale-gen, update-locale, dpkg-reconfigure locales
• iconv

Encodings to recognize:

• ASCII
• ISO-8859 (Latin-1, Latin-15)
• Unicode / UTF-8

7. Likely Exam Questions (Self-Check)

1. Where is the binary time zone database stored? /usr/share/zoneinfo/.

2. What two things can /etc/localtime be? Either a symlink to, or a copy of, a file under /usr/share/zoneinfo/.

3. How do you set the system time zone to Europe/Paris using systemd? timedatectl set-timezone Europe/Paris.

4. How do you override the time zone for a single command, without changing the system setting? Use the TZ environment variable, e.g. TZ=Asia/Tokyo date.

5. Which environment variable overrides all other locale settings? LC_ALL.

6. What is the precedence order between LANG, LC_TIME, and LC_ALL? LC_ALL > LC_TIME > LANG.

7. How do you list all locales installed on the system? locale -a.

8. What does setting LC_ALL=C do in a script, and why is it useful? It forces a plain POSIX/ASCII English locale. Output of commands becomes predictable, which is essential when scripts parse it.

9. Which Unicode encoding is the de facto standard on Linux? UTF-8.

10. How do you convert a file from ISO-8859-1 to UTF-8? iconv -f ISO-8859-1 -t UTF-8 input.txt -o output.txt.

11. On Debian, how do you enable and generate a new locale (e.g. fr_FR.UTF-8)? Uncomment it in /etc/locale.gen, then run locale-gen (or use dpkg-reconfigure locales).

12. What is the difference between the hardware clock and the system clock? The hardware clock is the battery-backed clock on the motherboard, read at boot. The system clock is maintained by the kernel while the system is running.

13. What command synchronizes the hardware clock from the system clock? hwclock --systohc.

14. A user reports date output in French. They want English just for their shell. What do they do? Add export LANG=en_US.UTF-8 (or export LC_ALL=en_US.UTF-8) to their ~/.bashrc or ~/.profile.

15. What is the practical difference between ASCII and UTF-8? ASCII has 128 single-byte characters. UTF-8 is a variable-length Unicode encoding that is fully backward-compatible with ASCII but can also represent every character in the Unicode standard.