Linux Files – Files Disappearing on Linux Server

auditdfileslinux

I've got 4 specific files that seem to keep disappearing from a user's home directory. As far as we know, there are no cronjobs or other automated tasks that would be removing them. I've setup auditd on them but the logs aren't really showing anything of interest. I can see our backup utility accessing them every night until the point they aren't there anymore, but nothing else. Is there anything that would be causing those files to be removed that would get around auditd?

The files in question are these:

/home/username/.bashrc
/home/username/.bash_profile

as well as a couple of files in that user's .ssh directory. Copies of these files placed into a subfolder called "keepers" get deleted at the same time as well. Changing the permissions on them to 000 and having them owned by root hasn't helped.

I've currently got inotifywait setup to log create,delete,move on that subfolder, so hopefully that will turn up something, although it doesn't log much aside from when it happened, not what caused it.

Best Answer

Solution 1: systemtap
You can use systemtap to show all PIDs that are trying to use unlink() on the inode of .bashrc and .bash_profile files.

Install systemtap and the debug symbols for your kernel.

Create a file with name unlink.stap with the following content:

probe syscall.unlink
{
    printf ("%s(%d) unlink (%s) userID(%d)\n", execname(), pid(), argstr, uid())
}

Then run it with sudo stap unlink.stap

Solution 2: inotify
You can also use inotify to see when the file is deleted.

Solution 3: ftrace
Another solution is to use ftrace:

trace-cmd record -e \*unlink\*

Wait for the file to be deleted, press CTRL+C to stop trace-cmd record ..., then run:

trace-cmd report

Solution 4: bpftrace
Install bpftrace, then run:

bpftrace -e 'tracepoint:syscalls:sys_enter_unlink* { printf("%s %s\n", comm, str(args->pathname)); }'
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