Introduction#
When I logged into a Ubuntu server, the system interface and messages are all shown in Chinese. I want them to be displayed in English. After some searching, I found out that we can change the locale settings.
The definition of locale is:
In computing, a locale is a set of parameters “Parameter”) that defines the user’s language, region and any special variant preferences that the user wants to see in their user interface
Set up locale for normal Linux system#
In Linux systems, there are several environment variables related to the locale
settings, such as LANG, LC_COLLATE, LC_TIME, LC_ALL etc. A valid locale
is like en_US.UTF-8. You can check
this documentation
on how locale is formed.
To see your default settings, use the locale command without any option. The
output looks like:
LANG=en_US.UTF-8
LANGUAGE=zh_CN:zh
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=
These settings are often pre-set by the system root. On CentOS, the system-wide
default locale settings are stored in /ect/locale.conf. On Ubuntu, the system
locale settings are store in /etc/default/locale.
Among the locale env variables, LC_xxx variables except LC_ALL are ordinary
environment variables that can be set individually.
Special variables are LANG, LANGUAGE and LC_ALL. Their priority are
listed here:
LANGUAGELC_ALLLC_xxx, according to selected locale category:LC_CTYPE,LC_NUMERIC,LC_TIME,LC_COLLATE,LC_MONETARY,LC_MESSAGES, …LANG
LANG is a special variable that will set the LC_* variable if it is not
set. LC_ALL will set all other LC_XXX variables to the same value. Usually,
you do not need to set up LC_ALL in your bash_profile. LANGUAGE is a
variable used for message handling, which has a higher priority than LC_ALL,
LC_xxx and LANG for messages (see the link [here](https: //www.gnu.org/software/gettext/manual/html_node/The-LANGUAGE-variable.html#The-LANGUAGE-variable))
. To verify this, suppose that we have the following settings inside
.bash_profile:
export LANG=en_US.utf8
export LANGUAGE=zh_CN.utf8
After sourcing the file, you will find that the messages given for command
output will be in Chinese (i.e., LANG is overridden.)
Set up locale for docker container#
Ubuntu docker#
I try to build a Ubuntu docker image. I want to set my locale to en_US.UTF-8
inside the container by simply adding the following ENV instruction:
ENV LC_ALL=en_US.UTF-8
When I run the built image, I get the following warning:
bash: warning: setlocale: LC_ALL: cannot change locale (en_US.UTF-8)
The locale command inside container gives the following message:
locale: Cannot set LC_CTYPE to default locale: No such file or directory
locale: Cannot set LC_MESSAGES to default locale: No such file or directory
locale: Cannot set LC_ALL to default locale: No such file or directory
LANG=
LANGUAGE=
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=en_US.UTF-8
It seems that the locale file en_US.UTF-8 does not exist inside container.
After some searching, I found the correct way to set up locales inside the
Ubuntu container. First, we need to install the locales package, which
provides the locale-gen command:
RUN apt-get update && apt-get install -y locales
After installing the locales packages, a file named local.gen will be
created under /etc. According to the documentation of locale-gen:
locale-gen is a program that reads the file /etc/locale.gen and invokes localedef for the chosen localisation profiles. Run locale-gen after you have modified the /etc/locale.gen file.
We should uncomment the line # en_US.UTF-8 UTF-8 in locale.gen and run
locale-gen command to generate the needed locale file. After that we can set
related settings to en_US.UTF-8:
RUN sed -i -e 's/# en_US.UTF-8 UTF-8/en_US.UTF-8 UTF-8/' /etc/locale.gen && \
locale-gen
ENV LC_ALL en_US.UTF-8
We can also directly generate the locale file by appending the locale as the
argument to locale-gen:
RUN locale-gen en_US.UTF-8
Putting this all together, we may use the following instructions inside Dockerfile:
RUN apt-get update && apt-get install -y locales && locale-gen en_US.UTF-8
CentOS docker#
If you tried to build an image based on a CentOS image. You need to use
localedef to generate locale files instead of locale-gen:
# -i: specify the locale definition file
# -f: specify the character set
RUN localedef -i en_US -f UTF-8 en_US.UTF-8
Other settings are similar to that of Ubuntu.