Command Linux

How to use sync command in Linux

There are two types of storage memories of the system; one is permanent memory and the other one is temporary memory which is RAM. The “sync” command is used to synchronize the data of the temporary memory to the permanent storage memory. The speed of RAM is faster than the permanent storage devices, therefore the system utilizes RAM instead of a hard disk to process the data, and in RAM the system stores the data in the form of cache.

Though storing the data on the RAM improves the speed of the system, in case of a sudden crash of the system there is a risk of losing the important data stored in the form of cache. It is better to synchronize the data on the permanent memory so, in case of any crash, there is no loss of data.

In this write-up, we will discuss the sync command used in Linux to synchronize the data of the RAM in the permanent storage.

How to use the sync command in Linux

The sync command is used for synchronizing the cache data to the hard disk, the general syntax of using the sync command:

$ sync [option] [file]

The sync command is used with options and then the file name of which the data has to be stored, the options used with the sync command are:

Options Explanation
-d, –data It is used to synchronize the file data of the file
-f, –file-system It is used to synchronize all the files which are linked to a given file
–help It displays the help options
–version It displays the version details of the command

To understand the usage of the sync command, we will perform some practical examples. First, we will sync all the data of the current user using the command:

$ sudo sync

It has synced all the cached files to the permanent memory which belongs to the current user, likewise, we have a text file in /home/hammad/mytestfile1.txt, we can sync its cache data using the command:

$ sync -d /home/hammad/mytestfile1.txt

To sync the files systems, we use the “-f” option in the command:

$ sync -f /home/hammad/Downloads

In the above command, we have synced all the files related to the /home/hammad/Downloads, we can also sync the cache data of the mounted partition (in our case it is sda1) using the command:

$ sudo sync /dev/sda1

The data of the mounted partition has been synced, likewise, we can also sync the log data of the /var/log/syslog using the command:

$ sudo sync /var/log/syslog

To check more details of the sync command we can use the “–help” option:

$ sync –help

Similarly, the “version” option is used to check the version of the sync command:

$ sync –version

Conclusion

The sync command is used in Linux to copy the data from the volatile memory which is in the form of cache to the permanent storage memory. The system saves all the data on the temporary memory because of its better speed as compared to the permanent storage devices, it is helpful but sometimes in case of unexpected shutdown of the system, a great risk is present of losing the data. To avoid this risk, it is recommended to sync the useful data from the temporary memory to the permanent memory. In this write-up, we have discussed the usage of the sync command in Linux with the help of examples for better understanding.

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