sync Command Cheat Sheet

sync synchronizes cached writes to persistent storage. It forces the kernel to write data buffered in memory out to disk.

Synopsis

sync [OPTION] [FILE]...

Flushes all file system buffers.

sync

Run this before pulling out a USB drive if you can't unmount it properly.

Only sync data related to specific files.

sync big_database.db

Sync the file system containing the file.

sync -f /mnt/usb/

Shutdown: valid shutdown, reboot, and halt commands automatically run sync.
Time: If you copy a massive file and run sync, the command prompt will hang until the write is physically complete.