There are several reasons why it's actually really unlikely to lose important data when you lose power on modern systems. Firstly, modern filesystems are desig

There are several reasons why it's actually really unlikely to lose important data when you lose power on modern systems. Firstly, modern filesystems are designed to be robust to random power loss, so it's unlikely that you will corrupt your filesystem in a way that cannot be recovered from. It does mean that some unflushed data would not be written, but it will only affect files that were opened for writing at or shortly before your system lost power. Some filesystems (including ext4) can offer quite strong consistency guarantees if you configure them correctly, though usually stronger consistency means lower performance in some scenarios. Secondly, the Linux regularly flushes dirty pages to disk anyway (15 seconds on my system, see `cat /proc/sys/vm/dirty_expire_centisecs` for yours) so you cannot lose more than a few seconds of data in the worst case. This is particularly important for the case of "oh, I forgot to unmount the USB stick before pulling it out of my laptop". Thirdly, most applications guard against data loss by using some form of write-ahead logging and explicit syncing. For example, if you edit a file in vim and then exit with `wq!` it will call fsync() before exiting, which causes the contents of the file to be flushed to disk immediately. In theory it's possibly that you lose power in the middle of the fsync() call, but it's extremely unlikely. (Of course it would be just as likely that you lose power right before issuing the write-and-quit command.) The sort of data that is not explicitly synced is where it's not really important to keep the latest information. Think about log files that are appended to continuously, or for example downloads in browsers. Do you really care if you have to restart an incomplete download after a sudden power loss? Probably not.