How to remove "dead.letter" File which left no free space in root directory

Question

1. Today I noticed that dead.letter file is created in my root directory on one of the EC2 instances.
2. After some look up I came to know that this is created because of some incomplete or terminated email functionality.
3. It has size of 6 GiB and it left no free space in root directory.
4. I have deleted the file still my root directory shows no free space available.

Any idea how to remove this file and free up the root space?

Answer 1

If you have removed it and the space still isn't freed, then it means a process has a file handle opened on it.

Try and find the PID of the process using, for instance:

for process in /proc/[0-9]*; do
    for fd in $process/fd/*; do
        file=$(readlink -f $fd)
        if [ "$file" = "/root/dead.letter" ]; then
            echo $process
        fi
    done
done

Then kill it/them.