Difference b/w hardware time and system time
I'd like to know the difference between Linux "hardware time" and "system time".
What time does the computer use from the point of view of a process querying it ?
Is it Hardware or system?
linux
edited 8 hours ago
jlliagre
47.4k784135
asked Mar 13 '15 at 6:56
vipin kumarvipin kumar
3931311
add a comment |
I'd like to know the difference between Linux "hardware time" and "system time".
What time does the computer use from the point of view of a process querying it ?
Is it Hardware or system?
linux
edited 8 hours ago
jlliagre
47.4k784135
asked Mar 13 '15 at 6:56
vipin kumarvipin kumar
3931311
It would be helpful if you refined your question. There are so many relations between the two times, yet there are also so many differences. "Which time does the computer use?" It uses both for different purposes. "What is the difference?" Here you need to clarify the perspective. Do you mean, from the point of view of a process? Or from the system administrator's perspective? Or something else?
– Run CMD
Mar 13 '15 at 8:23
From the point of view of a process..
– vipin kumar
Mar 13 '15 at 9:45
add a comment |
I'd like to know the difference between Linux "hardware time" and "system time".
What time does the computer use from the point of view of a process querying it ?
Is it Hardware or system?
linux
edited 8 hours ago
jlliagre
47.4k784135
asked Mar 13 '15 at 6:56
vipin kumarvipin kumar
3931311
I'd like to know the difference between Linux "hardware time" and "system time".
What time does the computer use from the point of view of a process querying it ?
Is it Hardware or system?
linux
linux
edited 8 hours ago
jlliagre
47.4k784135
asked Mar 13 '15 at 6:56
vipin kumarvipin kumar
3931311
edited 8 hours ago
jlliagre
47.4k784135
asked Mar 13 '15 at 6:56
vipin kumarvipin kumar
3931311
edited 8 hours ago
jlliagre
47.4k784135
edited 8 hours ago
jlliagre
47.4k784135
edited 8 hours ago
jlliagre
47.4k784135
47.4k784135
asked Mar 13 '15 at 6:56
vipin kumarvipin kumar
3931311
asked Mar 13 '15 at 6:56
vipin kumarvipin kumar
3931311
asked Mar 13 '15 at 6:56
vipin kumarvipin kumar
3931311
3931311
It would be helpful if you refined your question. There are so many relations between the two times, yet there are also so many differences. "Which time does the computer use?" It uses both for different purposes. "What is the difference?" Here you need to clarify the perspective. Do you mean, from the point of view of a process? Or from the system administrator's perspective? Or something else?
– Run CMD
Mar 13 '15 at 8:23
From the point of view of a process..
– vipin kumar
Mar 13 '15 at 9:45
add a comment |
It would be helpful if you refined your question. There are so many relations between the two times, yet there are also so many differences. "Which time does the computer use?" It uses both for different purposes. "What is the difference?" Here you need to clarify the perspective. Do you mean, from the point of view of a process? Or from the system administrator's perspective? Or something else?
– Run CMD
Mar 13 '15 at 8:23
From the point of view of a process..
– vipin kumar
Mar 13 '15 at 9:45
It would be helpful if you refined your question. There are so many relations between the two times, yet there are also so many differences. "Which time does the computer use?" It uses both for different purposes. "What is the difference?" Here you need to clarify the perspective. Do you mean, from the point of view of a process? Or from the system administrator's perspective? Or something else?
– Run CMD
Mar 13 '15 at 8:23
It would be helpful if you refined your question. There are so many relations between the two times, yet there are also so many differences. "Which time does the computer use?" It uses both for different purposes. "What is the difference?" Here you need to clarify the perspective. Do you mean, from the point of view of a process? Or from the system administrator's perspective? Or something else?
– Run CMD
Mar 13 '15 at 8:23
From the point of view of a process..
– vipin kumar
Mar 13 '15 at 9:45
From the point of view of a process..
– vipin kumar
Mar 13 '15 at 9:45
add a comment |
2 Answers
2
active
oldest
votes
The system time is maintained by the operating system, it is the one the processes will get when querying the date/time. Being stored in RAM, reading it is a fast operation.
The hardware time is maintained by a real clock powered by a battery. That means this clock persist a reboot. However, reading it implies performing a I/O operation which is more resource intensive than reading the system clock.
For that reason, the hardware clock is seldom used, mainly at boot time to set the system clock initial value, and then optionally to adjust/synchronize it either manually or through NTP.
Note that the hardware clock might be set to either the local time or UTC time while the system clock is always set on Unix/Linux systems to UTC time.
answered Mar 13 '15 at 10:10
jlliagrejlliagre
47.4k784135
1
This is a very clear and concise answer. Obviously the question leaves open several possibilities as to what a proper response might be but the @jlliagre has intelligently chosen a very clear and concise response.
– darbehdar
Oct 4 '16 at 5:14
add a comment |
Hardware time is depends Upon the BIOS ...the Bios battery controls that ..so when a system shutdown its also work ..
hwclock --show -->for hwd
date -->for sys
edited Mar 13 '15 at 9:04
Archemar
20.2k93772
answered Mar 13 '15 at 7:16
user106436user106436
1
"so when a system shutdown its also work" -- what's that suppose to mean???
– vipin kumar
Mar 13 '15 at 7:34
1
I guess that by 'so when a system shutdown its also work' you mean, hwclock still work when host is powered off (and battery still has power).
– Archemar
Mar 13 '15 at 9:06
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
The system time is maintained by the operating system, it is the one the processes will get when querying the date/time. Being stored in RAM, reading it is a fast operation.
The hardware time is maintained by a real clock powered by a battery. That means this clock persist a reboot. However, reading it implies performing a I/O operation which is more resource intensive than reading the system clock.
For that reason, the hardware clock is seldom used, mainly at boot time to set the system clock initial value, and then optionally to adjust/synchronize it either manually or through NTP.
Note that the hardware clock might be set to either the local time or UTC time while the system clock is always set on Unix/Linux systems to UTC time.
answered Mar 13 '15 at 10:10
jlliagrejlliagre
47.4k784135
1
This is a very clear and concise answer. Obviously the question leaves open several possibilities as to what a proper response might be but the @jlliagre has intelligently chosen a very clear and concise response.
– darbehdar
Oct 4 '16 at 5:14
add a comment |
The system time is maintained by the operating system, it is the one the processes will get when querying the date/time. Being stored in RAM, reading it is a fast operation.
The hardware time is maintained by a real clock powered by a battery. That means this clock persist a reboot. However, reading it implies performing a I/O operation which is more resource intensive than reading the system clock.
For that reason, the hardware clock is seldom used, mainly at boot time to set the system clock initial value, and then optionally to adjust/synchronize it either manually or through NTP.
Note that the hardware clock might be set to either the local time or UTC time while the system clock is always set on Unix/Linux systems to UTC time.
answered Mar 13 '15 at 10:10
jlliagrejlliagre
47.4k784135
1
This is a very clear and concise answer. Obviously the question leaves open several possibilities as to what a proper response might be but the @jlliagre has intelligently chosen a very clear and concise response.
– darbehdar
Oct 4 '16 at 5:14
add a comment |
The system time is maintained by the operating system, it is the one the processes will get when querying the date/time. Being stored in RAM, reading it is a fast operation.
The hardware time is maintained by a real clock powered by a battery. That means this clock persist a reboot. However, reading it implies performing a I/O operation which is more resource intensive than reading the system clock.
For that reason, the hardware clock is seldom used, mainly at boot time to set the system clock initial value, and then optionally to adjust/synchronize it either manually or through NTP.
Note that the hardware clock might be set to either the local time or UTC time while the system clock is always set on Unix/Linux systems to UTC time.
answered Mar 13 '15 at 10:10
jlliagrejlliagre
47.4k784135
The system time is maintained by the operating system, it is the one the processes will get when querying the date/time. Being stored in RAM, reading it is a fast operation.
The hardware time is maintained by a real clock powered by a battery. That means this clock persist a reboot. However, reading it implies performing a I/O operation which is more resource intensive than reading the system clock.
For that reason, the hardware clock is seldom used, mainly at boot time to set the system clock initial value, and then optionally to adjust/synchronize it either manually or through NTP.
Note that the hardware clock might be set to either the local time or UTC time while the system clock is always set on Unix/Linux systems to UTC time.
answered Mar 13 '15 at 10:10
jlliagrejlliagre
47.4k784135
answered Mar 13 '15 at 10:10
jlliagrejlliagre
47.4k784135
answered Mar 13 '15 at 10:10
jlliagrejlliagre
47.4k784135
answered Mar 13 '15 at 10:10
jlliagrejlliagre
47.4k784135
47.4k784135
1
This is a very clear and concise answer. Obviously the question leaves open several possibilities as to what a proper response might be but the @jlliagre has intelligently chosen a very clear and concise response.
– darbehdar
Oct 4 '16 at 5:14
add a comment |
1
This is a very clear and concise answer. Obviously the question leaves open several possibilities as to what a proper response might be but the @jlliagre has intelligently chosen a very clear and concise response.
– darbehdar
Oct 4 '16 at 5:14
1
1
This is a very clear and concise answer. Obviously the question leaves open several possibilities as to what a proper response might be but the @jlliagre has intelligently chosen a very clear and concise response.
– darbehdar
Oct 4 '16 at 5:14
This is a very clear and concise answer. Obviously the question leaves open several possibilities as to what a proper response might be but the @jlliagre has intelligently chosen a very clear and concise response.
– darbehdar
Oct 4 '16 at 5:14
add a comment |
Hardware time is depends Upon the BIOS ...the Bios battery controls that ..so when a system shutdown its also work ..
hwclock --show -->for hwd
date -->for sys
edited Mar 13 '15 at 9:04
Archemar
20.2k93772
answered Mar 13 '15 at 7:16
user106436user106436
1
"so when a system shutdown its also work" -- what's that suppose to mean???
– vipin kumar
Mar 13 '15 at 7:34
1
I guess that by 'so when a system shutdown its also work' you mean, hwclock still work when host is powered off (and battery still has power).
– Archemar
Mar 13 '15 at 9:06
add a comment |
Hardware time is depends Upon the BIOS ...the Bios battery controls that ..so when a system shutdown its also work ..
hwclock --show -->for hwd
date -->for sys
edited Mar 13 '15 at 9:04
Archemar
20.2k93772
answered Mar 13 '15 at 7:16
user106436user106436
1
"so when a system shutdown its also work" -- what's that suppose to mean???
– vipin kumar
Mar 13 '15 at 7:34
1
I guess that by 'so when a system shutdown its also work' you mean, hwclock still work when host is powered off (and battery still has power).
– Archemar
Mar 13 '15 at 9:06
add a comment |
Hardware time is depends Upon the BIOS ...the Bios battery controls that ..so when a system shutdown its also work ..
hwclock --show -->for hwd
date -->for sys
edited Mar 13 '15 at 9:04
Archemar
20.2k93772
answered Mar 13 '15 at 7:16
user106436user106436
1
Hardware time is depends Upon the BIOS ...the Bios battery controls that ..so when a system shutdown its also work ..
hwclock --show -->for hwd
date -->for sys
edited Mar 13 '15 at 9:04
Archemar
20.2k93772
answered Mar 13 '15 at 7:16
user106436user106436
1
edited Mar 13 '15 at 9:04
Archemar
20.2k93772
edited Mar 13 '15 at 9:04
Archemar
20.2k93772
edited Mar 13 '15 at 9:04
Archemar
20.2k93772
20.2k93772
answered Mar 13 '15 at 7:16
user106436user106436
1
answered Mar 13 '15 at 7:16
user106436user106436
1
answered Mar 13 '15 at 7:16
user106436user106436
1
1
"so when a system shutdown its also work" -- what's that suppose to mean???
– vipin kumar
Mar 13 '15 at 7:34
1
I guess that by 'so when a system shutdown its also work' you mean, hwclock still work when host is powered off (and battery still has power).
– Archemar
Mar 13 '15 at 9:06
add a comment |
"so when a system shutdown its also work" -- what's that suppose to mean???
– vipin kumar
Mar 13 '15 at 7:34
1
I guess that by 'so when a system shutdown its also work' you mean, hwclock still work when host is powered off (and battery still has power).
– Archemar
Mar 13 '15 at 9:06
"so when a system shutdown its also work" -- what's that suppose to mean???
– vipin kumar
Mar 13 '15 at 7:34
"so when a system shutdown its also work" -- what's that suppose to mean???
– vipin kumar
Mar 13 '15 at 7:34
1
1
I guess that by 'so when a system shutdown its also work' you mean, hwclock still work when host is powered off (and battery still has power).
– Archemar
Mar 13 '15 at 9:06
I guess that by 'so when a system shutdown its also work' you mean, hwclock still work when host is powered off (and battery still has power).
– Archemar
Mar 13 '15 at 9:06
add a comment |
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It would be helpful if you refined your question. There are so many relations between the two times, yet there are also so many differences. "Which time does the computer use?" It uses both for different purposes. "What is the difference?" Here you need to clarify the perspective. Do you mean, from the point of view of a process? Or from the system administrator's perspective? Or something else?
– Run CMD
Mar 13 '15 at 8:23
From the point of view of a process..
– vipin kumar
Mar 13 '15 at 9:45