How Do I Get Rid of /Sys/Kernel/Debug/Tracing?

Question

I have two Ubuntu 16.04.1 servers providing DHCP and DNS services on my network. Today, on one of my servers, I discovered a new filesystem mounted at /sys/kernel/debug/tracing. The other server, which is configured almost identically, does not have this filesystem mounted.

Why did this filesystem get mounted? How do I get rid of it?

> uname -a
Linux net-services-02 4.4.0-47-generic #68-Ubuntu SMP Wed Oct 26 19:39:52 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

> cat /proc/cmdline
BOOT_IMAGE=/vmlinuz-4.4.0-47-generic root=/dev/mapper/net--services--02--vg-root ro

> cat /etc/fstab
# /etc/fstab: static file system information.
# [... more comments ...]
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
/dev/mapper/net--services--02--vg-root /               ext4    errors=remount-ro 0       1
# /boot was on /dev/sda1 during installation
UUID=363b849e-4574-410a-acf9-e84c95d7d879 /boot           ext2    defaults        0       2
/dev/mapper/net--services--02--vg-swap_1 none            swap    sw              0       0

Accepted Answer

At first I thought the problem had something to do with your Linux net-services revealed by uname -a command. I'm on Ubuntu 16.04 desktop so had little hope I could solve these two questions. I read up on the situation from this link: (redhat.com - Realtime Tuning Guide) that discusses /sys/kernel/debug/tracing/

Must Read

Question 1: How did "debugfs on /sys/kernel/debug" get mounted?

Imagine my surprise learning on my system kernel tracing was also enabled:

# cat /proc/sys/kernel/ftrace_enabled
1

Also when I type mount, this is one of the lines that appears:

debugfs on /sys/kernel/debug type debugfs (rw,relatime)

I rebooted my kernel 4.4.0-47 to 4.4.0-45 then to 4.8.5 and finally to 3.13.0-92. ALL these versions have /sys/kernel/debug mounted.

To answer your question (paraphrased) "how did this happen?" -> it happens to everyone.

How Do I Get Rid of /Sys/Kernel/Debug/Tracing?

1 Answer

Must Read

Question 1: How did "debugfs on /sys/kernel/debug" get mounted?

Elena Rostova