Ubuntu – Is using the shutdown command to turn off the system safe

command linepower-managementshutdown

I have seen many articles and posts stating that a way to turn off the system via the terminal is issuing the shutdown -h now command. It obviously works on my system, but it shuts down everything extremely fast. If I power off the system using Ubuntu's GUI, the Ubuntu splash screen comes up, and it takes much more time before it actually powers down. By safe I am referring to a shutdown that makes sure all read/write operations are completed before powering down and avoiding data corruption.

So is using the shutdown command in the terminal actually a safe way to power off the system? If so, why does Ubuntu's shutdown menu take much longer to accomplish the same goal?

Best Answer

YES it is safe but...

Shutdown does more than simply flush unwritten data from RAM to disk. In some installations it can be setup to run custom jobs:

But as an answer here points out:

The shutdown halt option (designated by shutdown -h in your question) does flush all the buffers and safely unmount the disks but it doesn't actually turn off the machine. To do that use:

poweroff

halt means flush buffers, unmount drives, close all processes in a graceful way. But not power off (though some systems may power off anyway). So the hardware is still provided with power.

After halt a hard power off (pressing the power button or unplugging the power supply) will not damage the system, because it is already halted in a graceful way.

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