Making a directory protected from 'rm -rf'

Question

I just lost some data in folder A which was inside folder B after doing rm -rf B. Before I could realize what have I done, it was all over. Now a lesson is learnt, I wish to make some of my folder idiot-proof to avoid a next time when I do something similar and want to kill myself.

One way I can think of is to write a bash function and alias it to rm. This function will look into each sub-folder for a hidden file such as .dontdelete. When found, it would ask if I really want to continue. I can not make is write-protected since there is a process which constantly write to this folder. Is there any better way to do it?

Answer 1

In researching your question I came across this technique which might help you in the future.

You can apparently touch a file in the directory like so:

touch -- -i

Now when you run the command rm -fr * in a directory where the -i is present you'll be presented with the interactive prompt from rm.

$ ls
file1  file2  file3  file4  file5  -i

$ rm -fr *
rm: remove regular empty file `file1'? n
rm: remove regular empty file `file2'? n
rm: remove regular empty file `file3'? n
rm: remove regular empty file `file4'? n
rm: remove regular empty file `file5'? n

The same thing can be achieved by just leaving an alias in place for rm to always do rm -i. This can get annoying. So often what I've seen done is to have this alias in place, and then to disable it when you really want to delete without being prompted.

alias rm='rm -i'

Now in directories you'll be greeted like this:

$ ls
file1  file2  file3  file4  file5

$ rm -r *
rm: remove regular empty file `file1'?

To override the alias:

$ \rm -r *

This still doesn't stop a rm -fr however. But it does provide you with some protection.

References

• How to prevent yourself from accidentally deleting files in Unix/Linux

Answer 2

Many possibilities:

• alias rm='rm -i' - rm will ask - unless you specify -f...
• chmod -w dir - protects files directly in that directory.
• chattr +i if you really mean it
• write your own wrapper around rm
• etc...

But a better way is probably to have a good backup and keep important data in some kind of version control (like git), which brings a lot of other advantages, too.

Answer 3

Use a version control software like git to encapsulate your projects.

As long as you don't delete a whole project, you would have to purposefully type rm -rf .* to remove the .git directory and lose all the data needed for a rollback.

This has the added benefit that you can push backups of your stuff to a remote server like github or bitbucket.

Answer 4

Here's how rm -rf dir works:

1. It opens dir, and list its content.
2. For each entry, if it's a directory, repeat the same process for it, if it's not, call unlink on it.

If you could, for the directory listing, return a special filename first, and if you could cause a process doing an unlink on that file to die, that would solve the problem. That could be done using a fuse filesystem.

For instance, you could adapt the loopback.pl example from the perl Fuse module which just implements a dummy filesystem that is just a pass-through to a real file system underneath like so (see also patch below):

• when listing a directory, if it contains an entry named .{{do-not-delete}}., prepend the list of entries with two files: .{{do-not-delete}}!error and .{{do-not-delete}}!kill
• when trying to unlink the first one, return the EPERM code so that rm displays an error message
• when trying to unlink the second one, the process gets killed.

$ ls -Ff dir/test
./  .{{do-not-delete}}.  foo/  ../  bar
$ ./rm-rf-killer dir
$ ls -Ff dir/test
.{{do-not-delete}}!error  .{{do-not-delete}}!kill  ./  .{{do-not-delete}}.   foo/  ../  bar
$ rm -rf dir/test
rm: cannot remove `dir/test/.{{do-not-delete}}!error': Operation not permitted
zsh: terminated  rm -rf dir/test
$ ls -Ff dir/test
.{{do-not-delete}}!error  .{{do-not-delete}}!kill  ./  .{{do-not-delete}}.   foo/  ../  bar

Here a patch to apply on top of that loopback.pl example as a proof of concept:

--- loopback.pl 2013-06-03 22:35:00.577316063 +0100
+++ rm-rf-killer    2013-06-03 22:33:41.523328427 +0100
@@ -7,2 +7,4 @@
 my $has_threads = 0;
+my $flag = ".{{do-not-delete}}";
+
 eval {
@@ -42,3 +44,4 @@

-use blib;
+#use blib;
+use File::Basename;
 use Fuse;
@@ -49,3 +52,3 @@

-my %extraopts = ( 'threaded' => 0, 'debug' => 0 );
+my %extraopts = ( 'threaded' => 0, 'debug' => 0, 'mountopts' => 'nonempty' );
 my($use_real_statfs, $pidfile);
@@ -64,3 +67,7 @@

-sub fixup { return "/tmp/fusetest-" . $ENV{LOGNAME} . shift }
+sub fixup {
+    my $f = shift;
+    $f =~ s#(/\Q$flag\E)!(error|kill)$#$1.#s;
+    return ".$f";
+}

@@ -78,3 +85,9 @@
 }
-    my (@files) = readdir(DIRHANDLE);
+    my @files;
+    
+    while (my $f = readdir(DIRHANDLE)) {
+        unshift @files, "$flag!error", "$flag!kill"
+            if ($f eq "$flag.");
+        push @files, $f;
+    }
 closedir(DIRHANDLE);
@@ -121,3 +134,12 @@
 sub x_readlink { return readlink(fixup(shift));         }
-sub x_unlink   { return unlink(fixup(shift)) ? 0 : -$!; }
+sub x_unlink   {
+    my $f = shift;
+    if (basename($f) eq "$flag!error") {return -EPERM()}
+    if (basename($f) eq "$flag!kill") {
+        my $caller_pid = Fuse::fuse_get_context()->{"pid"};
+        kill("TERM", $caller_pid);
+        return -EPERM();
+    }
+    return unlink(".$f") ? 0 : -$!;
+}

@@ -203,3 +225,2 @@
 sub daemonize {
-    chdir("/") || die "can't chdir to /: $!";
 open(STDIN, "< /dev/null") || die "can't read /dev/null: $!";
@@ -236,2 +257,3 @@

+chdir($mountpoint) or die("chdir: $!");
 daemonize();
@@ -239,3 +261,3 @@
 Fuse::main(
-    'mountpoint'    => $mountpoint,
+    'mountpoint'    => '.',
 'getattr'       => 'main::x_getattr',

Answer 5

I have created a script to make this task easier. The shell script modifies the read/write permission and chattr flag of a given list of folders interactively, without asking root password. You can download the zip file from the link given below.

https://drive.google.com/file/d/0B_3UYBZy2FVsMVpBSWdSWnFBYk0/edit?usp=sharing

I have also included installation script to make the setup easier. Instructions are enclosed in the zip file.