Most modern Linux file systems support extended attributes. +s is secure deletion which ensures (at least intends) that the data in a file is overwritten with zeros when the file is deleted. Some file systems, NFS for example, do not yet support this feature, but they produce errors if you try to apply the attribute to their files or directories.
It has just come to my attention that certain underlying mechanisms, such as RAID controllers, SAN appliances or mechanical drives with SSD caches, might give a false sense of security by caching writes and possibly writing to different sectors without the logical file system having any visibility into the relocation.
- Is this concern real? Are there real world devices that create this vulnerability?
- Assuming such devices exist, do they perform in this manner all the time, or is it a statistical event that occurs occasionally, or is it a fluke that is only seen under special circumstances?