sync:tldr:63ad9

The "sync" command, short for "synchronize," is a utility that ensures all data in memory is written to the storage device, such as a hard drive or SSD. It is commonly used in Linux/Unix-based systems.

When you perform a write operation on a file or make changes to the file system, the changes are initially stored in memory buffers called caches. These buffers improve performance by reducing the number of disk writes.

However, for durability and data integrity, these changes need to be saved to the storage device. This is where the "sync" command comes into play. By executing "sync," you ensure that all modified data in the cache is written back to the disk immediately.

The "sync" command works by issuing a "flush" command to the operating system, which asynchronously writes the cached data to the storage device. Once the cache is safely written to disk, the command returns control to the user.

Using the "sync" command is particularly important before performing important system operations like shutting down or rebooting a system. It minimizes the risk of data loss, ensures that the filesystem is in a consistent state, and prevents any data corruption that may occur due to power failures or sudden system shutdowns.

In summary, the "sync" command acts as a safeguard to ensure that any modifications made in memory are properly saved to the storage device, thereby promoting data consistency and durability.