This chapter is from the book
This chapter is from the book
This chapter is from the book
Localization
Several commands can be used to display or modify the date and time on a system, as well as the locale of a system. This section explores these commands.
timedatectl
Use the timedatectl command to display the system clock.
Syntax:
timedatectl [option] [value]
Example:
[root@OCS ~]# timedatectl
Local time : Wed 2018-10-10 14:41:41 PDT
Universal time: Wed 2018-10-10 21:41:41 UTC
RTC time: Wed 2018-10-10 09:51:09
Timezone: America/Los_Angeles (PDT, -0700)
NTP enabled: yes
NTP synchronized: yes
RTC in local TZ: no
DST active: yes
Last DST change: DST began at
Sun 2018-03-11 01:59:59 PST
Sun 2018-03-11 03:00:00 PDT
Next DST change: DST ends (the clock jumps one hour backwards)
at
Sun 2018-11-04 01:59:59 PDT
Sun 2018-11-04 01:00:00 PST
As the root user, you can use this command to set the system clock. Table 7.4 demonstrates the most commonly used methods of changing the system clock.
TABLE 7.4 Methods to Change the System Clock
Method |
Description |
|---|---|
set-time [time] |
Sets the system clock to the specified time. |
set-timezone [zone] |
Sets the system time zone to the specified zone. |
set-ntp [0|1] |
Enables (1) or disables (0) Network Time Protocol. |
localectl
The BASH shell and other processes need customized operations to fit the location of the user. For example, if currency is to be displayed and the user is located in the United States, the $ character should be used. If the user is located in Great Britain, the £ character should be used.
This section focuses on the variables used to inform programs what settings to use based on a user’s locale.
LC_* refers to a collection of locale settings used to change the way the shell and other programs handle differences based on the geographic region of the user (or a region the user is familiar with). These values can be viewed by executing the locale command:
[root@OCS ~]# locale LANG=en_US.UTF-8 LANGUAGE=en_US 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=
The most important locale settings are described in Table 7.5.
TABLE 7.5 Locale Settings
Setting |
Description |
|---|---|
LANG |
Language |
LC_CTYPE |
Case conversion |
LC_NUMERIC |
Numeric format |
LC_TIME |
Time and date format |
LC_COLLATE |
Collation order |
LC_MONETARY |
Currency format |
LC_MESSAGES |
Format of message |
LC_PAPER |
Paper size format |
LC_NAME |
Name format |
LC_ADDRESS |
Address format |
LC_TELEPHONE |
Telephone format |
LC_ALL |
When set, LC_ALL will override all other locale settings. This provides an easy means to change all locale settings by modifying one environment variable. |
The localectl command can display and change both locale values and keyboard layouts.
Syntax:
localectl [options] command
To display values, use status:
[root@OCS ~]# localectl status
System Locale: LANG=en_US.utf8
VC Keymap: us
X11 Layout: us
X11 Model: pc105+inet
X11 Options: terminate:ctrl_alt_bksp
Set the locale and keyboard as follows:
[root@OCS ~]# localectl set-locale "LANG=de_DE.utf8"set-keymap "de"
There are a handful of options to the localectl command, but none of them are commonly used.
Cram Quiz
Answer these questions. The answers follow the last question. If you cannot answer these questions correctly, consider reading this chapter again until you can.
1. Which file can be revised to modify kernel parameters during the boot process?
A. /etc/sysctl.conf
B. /etc/kern.parm
C. /etc/kern.conf
D. /etc/sys.conf
2. Which command correctly sets the CD-ROM lock kernel parameter to 0?
A. sysctl dev.cdrom.lock 0
B. sysctl dev.cdrom.lock=0
C. sysctl dev/cdrom/lock=0
D. sysctl dev/cdrom/lock 0
3. Which of the following commands can be used to remove a module from memory? (Choose two.)
A. modprobe
B. insmod
C. modinfo
D. rmmod
4. Based on the following line from the /etc/rsyslog.conf file, which levels of messages for the cron service are logged?
cron.warn /var/log/cron
A. All levels
B. Just warn level
C. Warn level and levels with higher priorities
D. Warn level and levels with lower priorities
Cram Quiz Answers
1. A. The /etc/sysctl.conf file is used to specify which kernel parameters to enable at boot. The other answers are not valid kernel configuration files.
2. B. You can change the value of this parameter by using the sysctl command: sysctl dev.cdrom.lock=0. The character between dev, cdrom, and lock must be a ., not a / character. An equal sign must be between the parameter and the value.
3. A and D. The rmmod command is designed specifically to remove a module from memory. The -r option to the modprobe command also can be used to remove a module from memory. The insmod command inserts a module into memory, and the modinfo command provides details about a module.
4. C. When a priority is provided, it means “this priority and all priorities of a higher level.”