How to Quickly Check the System Uptime on Linux

Keeping an eye on how long your Linux system has been running is a staple of routine maintenance. Uptime tells you when the machine last rebooted—critical for troubleshooting, performance tuning, or simply confirming that scheduled reboots actually happened. In this post, you’ll learn four lightning-fast ways to check uptime without digging through logs.

1. Use the uptime Command

The simplest, most universal approach is the built-in uptime utility. Open your terminal and type:

$ uptime
 14:23:07 up 12 days,  5:17,  3 users,  load average: 0.05, 0.11, 0.09

Here’s what you’re seeing:

• Current time (14:23:07)
• How long the system’s been up (12 days, 5:17)
• Number of logged-in users (3 users)
• Load averages over the past 1, 5, and 15 minutes

No flags needed—uptime ships on all Linux distros and gives a quick glance at system health.

2. Check /proc/uptime Directly

Every running Linux kernel exposes uptime in /proc/uptime. To view it:

$ cat /proc/uptime
1046174.52 234567.89

• The first number is the total seconds since boot (e.g. 1,046,174.52s, or about 12 days).
• The second number is idle time in seconds.

If you want a human-friendly version, you can convert seconds into days, hours, and minutes with this one-liner:

$ awk '{printf("Uptime: %d days, %02d:%02d:%02d\n", $1/86400, ($1%86400)/3600, ($1%3600)/60, $1%60)}' /proc/uptime

3. Leverage the w Command

The w command shows who’s logged in and what they’re doing—but it also repeats uptime at the top. Just run:

$ w
 14:25:10 up 12 days,  5:19,  3 users,  load average: 0.05, 0.11, 0.09
USER     TTY      FROM             LOGIN@   IDLE   JCPU   PCPU WHAT
alice    pts/0    192.168.1.10     10:17    2:05m  0.03s  0.03s -bash

You get uptime plus user activity in one go—handy when you’re already checking who’s on the box.

4. Query Systemd’s Boot Time (For Systemd-based Distros)

If your distro uses systemd (most modern ones do), you can ask it directly when the system last booted:

$ systemd-analyze
Startup finished in 1.234s (kernel) + 2.345s (userspace) = 3.579s
$ systemd-analyze time
       Startup finished in 1.234s (kernel) + 2.345s (userspace) = 3.579s

To find the exact boot timestamp:

$ systemd-analyze show -p BootTimestamp
BootTimestamp=Thu 2025-06-07 08:15:30 +08

Subtract that from the current date to compute uptime, or simply note the timestamp if you need record keeping.

Bonus Tip: Use who -b for Last Reboot

Another quick check is the who command with the -b flag:

$ who -b
         system boot  2025-06-07 08:15

This tells you the exact date and time of the last system boot—perfect when precision matters.

Putting It All Together

• Fastest: uptime
• Raw data: cat /proc/uptime
• User overview: w
• Systemd details: systemd-analyze
• Reboot timestamp: who -b

Pick your tool based on need. For a quick health check, uptime wins every time. For scripting or parsing, /proc/uptime is unbeatable. And if you’re fully embracing systemd, systemd-analyze gives you rich timing info straight from the init system.

Ready to automate these checks? Drop a cron job that logs uptime every hour, or build a tiny monitoring script that emails you if your server uptime drops below a threshold. Whatever path you choose, now you know exactly how to get uptime in a pinch—no fuss, no fluff.

Mark Vincent

Tech enthusiast and content creator passionate about making technology simple for everyone. I share practical tips, guides, and reviews on the latest in computers, software, and gadgets. Let’s explore the digital world together!