tags 42440 + notabug
thanks
wrote:
> sometimes,rm can't delete the file.
> but when using rm -rf + file .
> the file can be deleted.
This does not sound like a bug in the rm command. Therefore I am
tagging this as such. If you have follow up information and this
turns out to be an actual bug then we can reopen the bug report.
Unfortunately there is not enough information in the report to know
exactly the case that you are talking about. For example I don't know
if you are talking about a literal "+" in that line or not. I will
assume that you are since it is there.
There are several FAQs listed for rm. Any of these might be a
problem.
https://www.gnu.org/software/coreutils/faq/coreutils-faq.html#How-do-I-remove-files-that-start-with-a-dash_003f
https://www.gnu.org/software/coreutils/faq/coreutils-faq.html#Why-doesn_0027t-rm-_002dr-_002a_002epattern-recurse-like-it-should_003f
You might have experienced either of those problems. Or a different
problem. We can't tell.
> sometimes,rm can't delete the file.
There are two main cases. One is that if the file is not writable by
the user then 'rm' will check for this and ask the user for
confirmation.
rwp@angst:/tmp/junk$ touch file1
rwp@angst:/tmp/junk$ chmod a-w file1
rwp@angst:/tmp/junk$ rm file1
rm: remove write-protected regular empty file 'file1'? n
rwp@angst:/tmp/junk$ ls -l file1
-r--r--r-- 1 bob bob 0 Jul 21 23:52 file1
The -f option will force it without prompting.
rwp@angst:/tmp/junk$ rm -f file1
rwp@angst:/tmp/junk$ ls -l file1
ls: cannot access 'file1': No such file or directory
This is a courtesy confirmation. Because the permissions on the file
is not important when it comes to removing a directory entry. A file
is really just an entry in the directory containing it. Removing a
file simply removes the entry from the directory. When the last link
to the file reaches zero then the file system reclaims the storage.
The file system is a "garbage collection" system using reference
counting.
https://en.wikipedia.org/wiki/Garbage_collection_(computer_science)
Therefore the only permission needed to remove a file is write
permission to the directory containing it.
rwp@angst:/tmp/junk$ touch file2
rwp@angst:/tmp/junk$ ls -ld . file2
drwxrwxr-x 3 rwp rwp 100 Jul 21 23:56 ./
-rw-rw-r-- 1 rwp rwp 0 Jul 21 23:56 file2
rwp@angst:/tmp/junk$ chmod a-w .
rwp@angst:/tmp/junk$ ls -ld . file2
dr-xr-xr-x 3 rwp rwp 100 Jul 21 23:56 ./
-rw-rw-r-- 1 rwp rwp 0 Jul 21 23:56 file2
This creates a file. The file is writable. But I have changed the
directory containing it not to be writable. This prevents the ability
to remove the file. Can't remove it because the directory is not wriable.
rwp@angst:/tmp/junk$ rm file2
rm: cannot remove 'file2': Permission denied
rwp@angst:/tmp/junk$ rm -f file2
rm: cannot remove 'file2': Permission denied
rwp@angst:/tmp/junk$ rm -rf file2
rm: cannot remove 'file2': Permission denied
rwp@angst:/tmp/junk$ ls -ld . file2
dr-xr-xr-x 3 rwp rwp 100 Jul 21 23:56 ./
-rw-rw-r-- 1 rwp rwp 0 Jul 21 23:56 file2
In order to remove the file we must have write permission to the
directory. Adding write permission to the directory allows removing
the file.
rwp@angst:/tmp/junk$ chmod ug+w .
rwp@angst:/tmp/junk$ rm file2
rwp@angst:/tmp/junk$ ls -ld file2
ls: cannot access 'file2': No such file or directory
Expanding upon this problem is if there are many directories deep and
the directories are not writable.
rwp@angst:/tmp/junk$ mkdir -p dir1 dir1/dir2 dir1/dir2/dir3
rwp@angst:/tmp/junk$ touch dir1/dir2/dir3/file3
rwp@angst:/tmp/junk$ chmod -R a-w dir1
rwp@angst:/tmp/junk$ find dir1 -ls
69649132 0 dr-xr-xr-x 3 rwp rwp60 Jul 22 00:00 dir1
69649133 0 dr-xr-xr-x 3 rwp rwp60 Jul 22 00:00
dir1/dir2
69649134 0 dr-xr-xr-x 2 rwp rwp60 Jul 22 00:00
dir1/dir2/dir3
69650655 0 -r--r--r-- 1 rwp rwp 0 Jul 22 00:00
dir1/dir2/dir3/file3
That sets up the test case. None of the directories are wriable.
Therefore we cannot remove any of them. The directory holding the
entries must be writable.
rwp@angst:/tmp/junk$ rm -rf dir1
rm: cannot remove 'dir1/dir2/dir3/file3': Permission denied
Even using 'rm -rf' does not work. And should not work. Because the
directories are not writable.
In order to remove these files the directories must be made writable.
rwp@angst:/tmp/junk$ chmod -R u+w dir1
rwp@angst:/tmp/junk$ rm -rf dir1
rwp@angst:/tmp/junk$ ls -ld dir1
ls: cannot access 'dir1': No such file or directory
Hopefully this helps you understand how directory entries work, that
the directory holding an entry (either file or another directory) must
be writable. How to add write permission. How to remove a single
file. How to remove a directory
