2023-06-05 - By Robert Elder
I use the 'sync' command to ensure that any cached writes are committed to persistent storage:
Here, I have an important piece of data that I want to back up to an external hard drive:
I use the 'cp' command to copy this data onto the external hard drive:
cp my-important-data.zip /external-drive/my-important-data.zip
As the 'cp' command runs, I no longer have control over the command prompt, but I can see that the destination file size is growing larger:
Eventually, the command prompt comes back and the destination file size stops increasing. 13 seconds later, I decide to unplug my external hard drive believing that the data has finished copying:
When I plug the drive back in, the file size is now smaller and the checksum doesn't match, indicating that the backup is corrupt:
That's why I always use the 'sync' command even if the drive activity light has stopped flashing:
After using the 'sync' command, the data will finish copying for a few seconds, and then return control to the prompt. Now, the file sizes are correct and the checksums match!
And that's why the 'sync' command is my favourite Linux command.
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