uptime¶
uptime
21:20:01 up 8 days, 18:26, 4 users, load average: 1.62, 1.62, 1.59
The three numbers are the load averages over 1, 5, and 15 minutes. w shows the same header plus who is logged in and what they are running. uptime -p prints "up 1 week, 1 day" and uptime -s prints the boot time.
How to read load¶
Load is the average number of tasks that wanted to run or were in uninterruptible sleep (usually disk I/O). Compare it with the number of CPU cores (nproc):
- Load around the core count means the CPUs are fully used with little queueing.
- Load well above the core count means tasks are waiting.
- On a single-CPU system the "full" value is 1.00. On an 8-core system it is 8.00.
- Compare the three values:
1.9, 1.2, 0.6is rising,0.6, 1.2, 1.9is recovering. - High load with idle CPU usually means storage or NFS stalls. Check iostat and
topforDstate processes.
See Linux load averages: solving the mystery.
Availability targets¶
Percentages translate to allowed downtime per year:
| Availability | Downtime per year | Per month (30 d) |
|---|---|---|
| 99% | 3.65 days | 7.2 hours |
| 99.9% | 8.76 hours | 43.2 minutes |
| 99.95% | 4.38 hours | 21.6 minutes |
| 99.99% | 52.6 minutes | 4.3 minutes |
| 99.999% ("five nines") | 5.26 minutes | 26 seconds |
An online calculator for other targets: uptime.is.