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512be89796
Introduce the DNS Kconfig symbol so that various network commands may use host names without the dns command (CMD_DNS) being selected. Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org> CC: E Shattow <e@freeshell.de>
73 lines
1.9 KiB
ReStructuredText
73 lines
1.9 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+:
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.. index::
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single: sntp (command)
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sntp command
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============
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Synopsis
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--------
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::
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sntp [serverip]
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sntp [servername] # NET_LWIP=y && DNS=y only
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Description
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-----------
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The sntp command gets the current time from an NTP time server and
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syncronizes the Real Time Clock (RTC) of the board. This command needs
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the server's IP address to be given on the command line or via the
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`ntpserverip` environment variable.
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The address of the NTP server does not need to be given if the DHCP server
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provides one. The legacy network stack (`CONFIG_NET=y`) can only use the
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first NTP server provided in the `ntp-servers` DHCP option.
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When the network stack is lwIP (`CONFIG_NET_LWIP=y`) and DNS resolution
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is enabled (`CONFIG_DNS=y`), then the sntp command accepts a server
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name as an argument.
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The network time is sent as UTC. So, if you want to set the RTC to any local
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time different from UTC, you need to set the `timeoffset` environment variable.
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Round-trip delay compensation is not implemented/not enabled. In practice
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this should not matter much given that the RTC API does not have sub-second
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resolution, and round-trip times are typically 10 to 100 ms at most.
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Examples
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--------
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::
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=> setenv ntpserverip 109.190.177.205
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=> date
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Date: 2025-06-16 (Monday) Time: 15:19:35
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=> date reset
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Reset RTC...
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Date: 2000-01-01 (Saturday) Time: 0:00:00
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=> date
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Date: 2000-01-01 (Saturday) Time: 0:00:03
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=> sntp
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Date: 2025-06-16 Time: 15:19:43
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=> date
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Date: 2025-06-16 (Monday) Time: 15:19:47
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=> setenv timeoffset 7200
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=> sntp
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Date: 2025-06-16 Time: 17:19:55
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=> date
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Date: 2025-06-16 (Monday) Time: 17:19:57
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With `CONFIG_NET_LWIP=y` and `CONFIG_DNS=y`:
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::
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=> date reset
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Reset RTC...
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Date: 2000-01-01 (Saturday) Time: 0:00:00
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=> sntp 0.us.pool.ntp.org
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Date: 2025-06-16 Time: 15:10:59
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