How long has my Linux system been running?

Is there a command I can type in a terminal that will tell me the last time a machine was rebooted?

Answers:

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Method 1

uptime

If you want it in numerical form, it’s the first number in /proc/uptime (in seconds), so the time of the last reboot is

date -d "$(</proc/uptime awk '{print $1}') seconds ago"

The uptime includes the time spent in a low-power state (standby, suspension or hibernation).

Method 2

You can use uptime or last

To see only the last time

last reboot -F | head -1 | awk '{print $5,$6,$7,$8,$9}'

more generically

last reboot

Note and warning

The pseudo user reboot logs in each time the system is rebooted.  
Thus last reboot will show a log of all  reboots since the log file was created.

Method 3

I usually use who -b, which produces output such as:

$ who -b
         system boot  2014-05-06 22:47
$

It tells me the date and time when the machine was last booted, rather than the time that has elapsed since it was last booted.

This command works on many other Unix systems too (Solaris, …).

Method 4

With the uptime implementation from procps 3.3.6 or newer, this will perfectly do what you want:

$ uptime --since
2018-07-24 09:22:50

Method 5

Use tuptime, you get all the information that you need, for example:

$ tuptime -e
Startup:  1  at  08:03:58 10/08/15
Uptime:   6 hours, 56 minutes and 7 seconds
Shutdown: OK  at  15:00:05 10/08/15

Downtime: 17 hours, 8 minutes and 14 seconds

Startup:  2  at  08:08:20 11/08/15
Uptime:   6 hours, 51 minutes and 38 seconds
Shutdown: OK  at  14:59:58 11/08/15

Downtime: 17 hours, 7 minutes and 46 seconds

Startup:  3  at  08:07:45 12/08/15
Uptime:   6 hours, 50 minutes and 47 seconds
Shutdown: OK  at  14:58:32 12/08/15

Downtime: 17 hours, 5 minutes and 18 seconds

Startup:  4  at  08:03:51 13/08/15
Uptime:   6 hours, 55 minutes and 12 seconds
Shutdown: OK  at  14:59:03 13/08/15

Downtime: 17 hours, 14 minutes and 20 seconds

Startup:  5  at  08:13:24 14/08/15
Uptime:   1 hours, 28 minutes and 14 seconds

System startups:    5   since   08:03:58 10/08/15
System shutdowns:   4 ok   -   0 bad
Average uptime:     5 hours, 48 minutes and 24 seconds
Average downtime:   13 hours, 43 minutes and 7 seconds
Current uptime:     1 hours, 28 minutes and 14 seconds   since   08:13:24 14/08/15
Uptime rate:        29.74 %
Downtime rate:      70.26 %
System uptime:      1 days, 5 hours, 2 minutes and 1 seconds
System downtime:    2 days, 20 hours, 35 minutes and 39 seconds
System life:        4 days, 1 hours, 37 minutes and 40 seconds

Method 6

Just open a terminal and type “top” : read at the top of the screen for the uptime.

Method 7

If procinfo is installed, you can also use:

$ procinfo | grep Bootup
Bootup: Mon Sep 26 09:27:26 2016   Load average: 0.68 1.10 1.67 2/2783 4828

You can install it with sudo apt-get install procinfo

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0