|
Size: 1258
Comment:
|
Size: 1038
Comment:
|
| Deletions are marked like this. | Additions are marked like this. |
| Line 1: | Line 1: |
| = System Clock in Linux = | = Linux Clock = |
| Line 3: | Line 3: |
| The '''system clock''' in Linux generally uses the '''Coordinated Universal Time ''' ('''UTC''') standard, as opposed to '''localtime'''. Linux images often come with a wonky clock setting based on when the image was generated. This can cause significant issues on web servers, as signed SSL certificates are only valid within a date range. |
On Linux, the '''clock''' generally uses UTC time with a timezone offset in software, as opposed to local time. |
| Line 14: | Line 11: |
| == Date and Time == Use '''`date(1)`''' as the root user to set the current date and time. {{{ # January 1st, 2001 at 12:30 sudo date 0101011230 }}} Use '''`hwclock(1)`''' or [[TimeDateCtl|timedatectl(1)]] to check the CMOS clock. ---- |
|
| Line 16: | Line 28: |
| For `systemd`-capable systems, use '''`timedatectl(1)`''' to set the local timezone. Substitute `America/New_York` with your preferred configuration. | The configured timezone is set in `/etc/localtime`. By standard convention, this should be a symbolic link to a pre-prepared file, typically under `/usr/share/zoneinfo`. |
| Line 18: | Line 30: |
| {{{ timedatectl status timedatectl list-timezones timedatectl set-timezone America/New_York }}} `timedatectl(1)` is a simple utility script; the manual equivalents roughly are... |
To check the current configuration, try: |
| Line 28: | Line 34: |
| ls /usr/share/zoneinfo/* | }}} To change the configuration, try: {{{ |
| Line 31: | Line 41: |
For `systemd`-capable systems, consider using [[TimeDateCtl#Timezone|timedatectl(1)]]. |
|
| Line 39: | Line 51: |
| ---- == Date and Time == Use '''`date(1)`''' to set the current datetime. Note that `date(1)` must be called by the root user to set a datetime. {{{ # January 1st, 2020 at 12:30 sudo date 2001011230 }}} |
Linux Clock
On Linux, the clock generally uses UTC time with a timezone offset in software, as opposed to local time.
Contents
Date and Time
Use date(1) as the root user to set the current date and time.
# January 1st, 2001 at 12:30 sudo date 0101011230
Use hwclock(1) or timedatectl(1) to check the CMOS clock.
Timezone
The configured timezone is set in /etc/localtime. By standard convention, this should be a symbolic link to a pre-prepared file, typically under /usr/share/zoneinfo.
To check the current configuration, try:
realpath /etc/localtime
To change the configuration, try:
ln -sf /usr/share/zoneinfo/America/New_York /etc/localtime
For systemd-capable systems, consider using timedatectl(1).
Some utilities will also respect a TZ environment variable.
export TZ=America/New_York date