preventing deletion of an opened file
Is it possible to prevent a file from deletion, if that file is opened by a process ?
All operations are performed by "root".
processA opened "foo.bin"
I want "rm foo.bin" can not delete this file.
The only way mandatory locking ?
If you're worried about the program failing because the blocks on disk might get removed while it's running, don't. On unix-like systems file data is only purged from disk when the link count reaches 0. Having a file in a directory raises the link count by one. So does having an open file handle for that file. While the program is running, even if the file is removed from the directory where it exists, the link count will still not drop to 0 because there is an open file handle for that file. Only when the program finishes and the file handle to the file is closed will the data be removed from the disk.
If you simply want to stop people removing the file from the directory, just change the permissions:
In fact, the problem is
processA continuously writes some kind of log to "foo.bin". If you remove file, processA does'nt know it. And write system call does'nt give any error although when you look at /proc/<pid>/fd, the file has (deleted) info near its name. You can use inotify maybe to close/re-open again that file to continue to logging. Or prevent totally the deletion of this log file. Since flock is an advisory lock, it does'nt work.
chattr -i file
Also, if you get the file creator ie logging prog to immediately unlink (delete) the file after opening it, it will be invisible to other cmds (I think).
This is often used to create temp files that can't be interfered with by other processes.
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