USB key falls into read-only file system

[GreyGeek]

....
What the hell kind of file system can be read-only to root?

FYI - https://www.tecmint.com/chattr-command-examples/

[vinnywright]

Read-only file system

may also mean that the sticks were mounted read-only !

what file system is on them and (with them mounted and accessible) what dose

findmnt

show ?

VINNY

[Snowhog]

How are you creating the backups on the device? A program or manually? If a program, which one? If manually, what command(s) are you using?

[joneall]

Your file has either an i and/or an a attribute attached (immutable or append).

What in the world are those? I know about unix (so, linux) file and directory permissions (drwxrwxrwx...), but never heard of i or a attributes. Does Linux/Ubuntu support those?

And why would they have been applied to my file system just shortly after I wrote to it?

I really would like to query such attributes before deleting the files. I tried lsattr, to no avail.

$ lsattr -d T321
lsattr: Inappropriate ioctl for device While reading flags on T321

[GreyGeek]

Your file has either an i and/or an a attribute attached (immutable or append).
chattr -i xx
chattr -a xx

Then delete it.

PS - If that doesn't work then the directory it is in has one or both of those attributes.
Use
lsattr -d T321
to check the attributes.
chattr -d -suSiadAc T321
will remove all of them.

[joneall]

Sorry if the subject is not clear. The point is, I have USB keys to which I can write, but when I want to erase the same file later, they have become read-only file systems. The one in question is /media/jon/T321:

$ pwd; ll
/media/jon
total 36
drwxr-x---+ 6 root root    4096 avril 27 10:01 ./
drwxr-xr-x  3 root root    4096 févr. 21  2017 ../
drwxr-xr-x  8 jon  sjuser 16384 janv. 1  1970 T321/

$cd T321
ls -ld backups/
drwxr-xr-x 7 jon sjuser 16384 avril 27 10:01 backups/

$ cd backups/
l$ ll
total 112
drwxr-xr-x 7 jon sjuser 16384 avril 27 10:01 ./
drwxr-xr-x 8 jon sjuser 16384 janv. 1  1970 ../
drwxr-xr-x 3 jon sjuser 16384 avril 15 21:15 180415/
drwxr-xr-x 3 jon sjuser 16384 avril 27 10:02 180419/
drwxr-xr-x 3 jon sjuser 16384 avril 22 18:04 180422/
drwxr-xr-x 4 jon sjuser 16384 avril 23 18:26 180423/
drwxr-xr-x 2 jon sjuser 16384 avril 27 10:00 180426/

-rw-r--r-- 1 jon sjuser     0 avril 27 10:01 xx
jon@jon-neon:/media/jon/T321/backups$

As you can see, I just created file xx today, but I can not erase it or modify it, not even as root.

$ sudo chmod 755 xx 
chmod: changing permissions of 'xx': Read-only file system

What the hell kind of file system can be read-only to root?