16.04 - How do I get rid of /sys/kernel/debug/tracing? - Ask Ubuntu


i have 2 ubuntu 16.04.1 servers providing dhcp , dns services on network. today, on 1 of servers, discovered new filesystem mounted @ /sys/kernel/debug/tracing. other server, configured identically, not have filesystem mounted.

why did filesystem mounted? how 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 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

at first thought problem had linux net-services revealed uname -a command. i'm on ubuntu 16.04 desktop had little hope solve these 2 questions. read on situation link: (redhat.com - realtime tuning guide) discusses /sys/kernel/debug/tracing/

question 1: how did "debugfs on /sys/kernel/debug" mounted?

imagine surprise learning on system kernel tracing enabled:

# cat /proc/sys/kernel/ftrace_enabled 1

also when type mount, 1 of lines appears:

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

i rebooted kernel 4.4.0-47 4.4.0-45 4.8.5 , 3.13.0-92. all these versions have /sys/kernel/debug mounted.

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

question 2: how rid of it?

to answer question "how rid of it?", use:

sudo umount debugfs

note works current session.

summary thoughts

even though trace enabled on ubuntu kernel versions i've tested, not activated until tell start monitoring specific event. after event activated slow down cpu.

basically not worry this...


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