Calibrating a display has to be done on a regular basis to account for display aging.
Calibration has to be done if the ambient light falling on the display has changed.
Ouch! Color management on a Linux system -- ouch! Ultimately there's not a fully functional option (unless you can write your own software).
Monitor calibration requires an external hardware device (colorimeter or spectrophotometer) and software to operate that device.
Caution: Anyone who tells you the external hardware isn't required is clueless.
To my knowledge no company that makes the hardware supports (software) Linux. That leaves you with purchasing the hardware and then solving the software support option:
1. You're using Linux so write your own software. (Share what you come up with.)
2. Find some other geek who already did #1: ArgyllCMS
3. Figure out an inventive kludge.
I maintain a Linux system to run specific software I can't get on Windows and I had the same problem. I went with option #3. The key for me was that I'm running Linux on the same hardware I use for Windows -- same computer, same video, same monitor. So my Windows system is color managed and my monitor is calibrated and profiled running Windows. That allowed me to copy the monitor ICC profile from my Windows system and install it on the Linux system including targeting it in the Linux photo software I'm using -- worked.