|
Size: 1058
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: |
| == Timezone == | == Date and Time == |
| Line 16: | Line 13: |
| Use '''`timedatectl(1)`''' to set the local timezone. | Use '''`date(1)`''' as the root user to set the current date and time. |
| Line 19: | Line 16: |
| timedatectl status timedatectl list-timezones timedatectl set-timezone ZONE/SUBZONE |
# January 1st, 2001 at 12:30 sudo date 0101011230 |
| Line 24: | Line 20: |
| `timedatectl(1)` is a simple utility script; the manual equivalents roughly are... {{{ realpath /etc/localtime ls /usr/share/zoneinfo/* ln -sf /usr/share/zoneinfo/Zone/SubZone /etc/localtime # apply a new setting }}} |
Use '''`hwclock(1)`''' or [[TimeDateCtl|timedatectl(1)]] to check the CMOS clock. |
| Line 36: | Line 26: |
| == Date == | == Timezone == |
| Line 38: | Line 28: |
| Use '''`date(1)`''' to set the current datetime. Note that `date(1)` must be called by the root user to set a datetime. | 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: |
| Line 41: | Line 33: |
| # January 1st, 2020 at 12:30 sudo date 2001011230 |
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#Timezone|timedatectl(1)]]. Some utilities will also respect a `TZ` environment variable. {{{ export TZ=America/New_York date |
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