26

I tried to change the tcp timestamps in Ec2 instance (which is Ubuntu 12.04). I opened up the editor and changed the value 1 from 0. And when I tried to save the file I get this error:

/proc/sys/net/ipv4/tcp_timestamps" E667: Fsync failed

I'm very new to Ubuntu. Can anyone help me in this out?

Jeremy Kerr
  • 27,879
batman
  • 8,101

4 Answers4

35

Your editor is probably doing funny things to that file (files in /proc are not actual files, they're an interface to lower-levels of the operating system). While the change is probably working okay, the usual way of updating things in proc is directly with a shell command, like:

echo 1 | sudo dd of=/proc/sys/net/ipv4/tcp_timestamps

If you want this setting to be applied every time you boot, create a file called /etc/sysctl.d/tcp-timestamps.conf, containing the following:

net.ipv4.tcp_timestamps = 1
Jeremy Kerr
  • 27,879
  • 3
    This pattern (echo VALUE | sudo dd of=/path/to/file) is very useful. Thank you very much! – Malcolm Sep 10 '13 at 00:23
  • 1
    Worked for me too for this and to set other kernel parameters. This helped for setting another kernel parameter called allow_tpm. echo 1 | sudo dd of=/sys/module/libata/parameters/allow_tpm –  Nov 17 '14 at 22:47
  • 1
    What is the purpose of dd of? All I understand is the echo and the pipe, but I don't understand why dd was needed. Why not > instead? – Adelin Dec 27 '18 at 10:21
  • 1
    @Adelin The dd is there to perform the write as root. The rest of the command pipeline does not need to be privileged, so dd is the only part that we run under sudo.

    If we were to run the entire shell as root, the > redirection would be fine. But I like to minimise what is run with root privs.

     – Jeremy Kerr Jan 08 '19 at 01:55
21

Sometime back we were getting exact same error. After wasting several minutes in investigation found there was no space left on the device. You can check if it is the case for you. Try freeing up some storage to quickly fix the issue.

Note: This could not be the best technical description of the problem but it might help in quickly fixing the issue. The verified answer explain this in more detail. My answer was just to share how I fixed this issue.

NIVESH SENGAR
  • 311
4

I see this was correctly answered a long time ago, but there is simpler command:

sudo sysctl net.ipv4.tcp_timestamps=1

Also you can do the same with other settings like:

sudo sysctl vm.admin_reserve_kbytes=16384

As you can see, you can modify any file in /proc/sys/ by specifying the rest of its location, while changing delimiter from "/" to "."

Example: "/proc/sys/net/ipv4/tcp_timestamps" is specified as "net.ipv4.tcp_timestamps"

user8542574
  • 41
3

Fsync failed WARNING: Original file may be lost or damaged don't quit the editor until the file is successfully written!

Could be a space issue as clearing a couple of files worked for me

Bandana D
  • 31