Why must a 'user.' be prepended to the name when setting a file's xattr with os.setxattr()?
Question:
I am saving data that I guess could be deemed metadata on a JSON serialized file:
os.setxattr('/var/tmp/test.json', 'user.keyname', b'value')
and I can get the bytes value back via:
os.getxattr('/var/tmp/test.json', 'user.keyname')
The only way I can get this to work is by putting user. in front of the key/name that I want to use. Why is this?
Answers:
https://jp-andre.pagesperso-orange.fr/extend-attr.html
On Linux, specifically, four categories of extended attributes have been defined :
- trusted: to record properties which should only be accessed by the kernel,
- security: to record security properties of a file,
- system: to record other system related properties on which the file owner has some control,
- user: to record properties defined by applications.
The names of the extended attributes must be prefixed by the name of the category and a dot, hence these categories are generally qualified as name spaces.
I am saving data that I guess could be deemed metadata on a JSON serialized file:
os.setxattr('/var/tmp/test.json', 'user.keyname', b'value')
and I can get the bytes value back via:
os.getxattr('/var/tmp/test.json', 'user.keyname')
The only way I can get this to work is by putting user. in front of the key/name that I want to use. Why is this?
https://jp-andre.pagesperso-orange.fr/extend-attr.html
On Linux, specifically, four categories of extended attributes have been defined :
- trusted: to record properties which should only be accessed by the kernel,
- security: to record security properties of a file,
- system: to record other system related properties on which the file owner has some control,
- user: to record properties defined by applications.
The names of the extended attributes must be prefixed by the name of the category and a dot, hence these categories are generally qualified as name spaces.