However, there are two exceptions:ĭuring the period you run sudo mv test_file /dev/null and cp /dev/null our_test_file, if any root script in the system overwrites it by running echo "Whatever text the root script wants to send to /dev/null" > /dev/null (or other similar commands). So, it is impossible to move a directory to /dev/null and hence there is no question of recovering the directory from there.Īs far as files are concerned, if you directly move files to /dev/null, you can still recover it as demonstrated above. If you didn't create /tmp/null and tried those commands directly using /dev/null make sure you recover the file (if you need to) by running cp /dev/null our_test_file and restore /dev/null for the purposes it exists on our system by running the following commands as given in the linked question as soon as possible: $ sudo rm /dev/null We can recover our file by copying /tmp/null just like any other file: $ cp /tmp/null our_test_file So, it is still there and /tmp/null which was a special file has been overwritten and it has become like any other normal file. Let us test if we can recover our test_file. Now, let us figure if we can recover our test_file from /tmp/null: $ cat /tmp/null Test_dir is still present inside ask_ubuntu: $ ls -la Mv: cannot overwrite non-directory ‘/tmp/null’ with directory ‘test_dir/’ Now try to move test_dir to /tmp/null which doesn't succeed: $ sudo mv test_dir/ /tmp/null The command succeeds and test_file is no longer available. Now try to move our test_file to /tmp/null and see the contents of ask_ubuntu: $ sudo mv test_file /tmp/null # This succeedsĭrwxr-xr-x 3 aditya aditya 4096 Mar 18 17:12. rw-r-r- 1 aditya aditya 0 Mar 18 17:10 test_file ĭrwxr-xr-x 2 aditya aditya 4096 Mar 18 17:10 test_dir
The following shows the contents of ask_ubuntu directory: $ ls -laĭrwxr-xr-x 3 aditya aditya 4096 Mar 18 17:10. $ echo "Let us test if we can recover our test_file." > test_file Let us create a test_file and a test_dir inside a directory called ask_ubuntu. Now onwards, /tmp/null is our /dev/null for all purposes: So, let's create /tmp/null and use it for our experimentation purposes: sudo mknod -m 0666 /tmp/null c 1 3
#Blackhole devnull facebook email how to#
I can read from /dev/null how to fix it?Īs suggested by in this answer to that question, in order to experiment with /dev/null we should rather create a copy of it and then do our experimentation.However, since you want to experiment with /dev/null, you are first suggested to know the consequences to moving a file to overwrite /dev/null and how to recover from that situation: If you try moving a directory to /dev/null it would report an error since /dev/null is not a directory but a file. You can write files or other input streams to /dev/null but not directories. Having this assumption broken can lead to random data (well, the data the last process wrote to `/dev/null') inserted in system files all around the system - which could lead to an utterly broken and unrecoverable system. The most dangerous effect of this change is that /dev/null is supposed to never output any data, so a number of shell script will assume that `.
$ mv /path/to/afile /dev/nullĪfter this command, /dev/null is a regular file. $ cp ~/bzip2_1.0.6-4_b /dev/nullĬrw-rw-rw- 1 root root 1, 3 Mar 16 14:25 nullĪbout the only thing you can do to this file is copy mv over it another file or delete it. You can't copy onto /dev/null either, given it's a character file, if you try to copy a regular file onto it. Mv: cannot overwrite non-directory ‘afile’ with directory ‘dir’ The mv command won't allow this since you're moving a directory to a file, that just doesn't make sense contextually and mv knows this. That being said you could never run this command: $ mv ~ /dev/null dev/null is just a file, it's a "special character" file but it's non the less still bound by the rules that files must follow.
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