From a UPS Move to Linux Uptime: Understanding the uptime Command and Load Average

Uptime command overview

The Linux uptime utility reports how long the system has been running, the number of users currently logged in, and the system load averages for the past 1, 5, and 15 minutes. It is part of the procps-ng package.

Common options

-V

: Display version information and exit.

Example usage

# uptime -V
uptime from procps-ng version 3.3.17
# uptime
15:31:30 up 127 days,  3:00,  1 user,  load average: 0.00, 0.00, 0.00

Explanation of output fields

15:31:30               # current system time (HH:MM:SS)
up 127 days, 3:00    # total time the kernel has been running since the last boot
1 user                # number of active login sessions (not distinct users)
load average: 0.00, 0.00, 0.00  # average number of processes in the run queue over the last 1, 5, and 15 minutes

Understanding load average

The load average represents the average number of processes that are either running on the CPU or waiting for CPU time. It is a useful indicator of overall system demand.

Interpretation guidelines:

On a single‑core system, a load average of 1.0 means the CPU is fully utilized. Values below 1.0 indicate idle capacity; values above 1.0 indicate queuing.

On multi‑core systems, divide the load average by the number of CPU cores to obtain a per‑core load. For example, on a dual‑core machine, a load average of 2.0 corresponds to full utilization (2 / 2 = 1 per core).

As a rule of thumb, a per‑core load ≤ 3 is considered acceptable for most workloads. Persistent per‑core loads > 5 suggest the system is overloaded and may require performance tuning or additional resources.

Example: a dual‑core server reporting load average: 6.00, 6.00, 6.00 indicates each core is handling an average of three processes (6 / 2 = 3), which is near the upper bound of comfortable operation.

Author: 行动的大雄 Reference: https://www.theregister.com/2025/11/21/on_call/?td=rt-3a