systemd-fsckd : useless CR displayed on console

[Laurent]

Hello,

My system is "Ubuntu 16.04.2 LTS" (grep DISTRIB_DESCRIPTION /etc/lsb-release).

The systemd package is installed:
  $ dpkg -l | grep systemd
  > systemd 229-4ubuntu17

I noticed that approximately 15 seconds after the boot, a useless
Carriage Return ('\r') is displayed on the console (/dev/console).
This character interacts with the display of the user currently logued in
on the console. This screws the current line, when users is pressing keys.

After monitoring system activity, I found the culprit:
  /lib/systemd/system/systemd-fsckd.service

To test, run:
  service systemd-fsckd stop # In case, it is still running.
  service systemd-fsckd start
Go to the console, wait for approximately 15 seconds, and you see the cursor
jumping from its current position to the beginning of the line. This is the BUG.
Note: the console is not the X11 terminal (xterm, lxterminal, etc.) ; the
console is the text tty reached with Control-Alt-F1.

The systemd-fsckd.service starts the following daemon:
  /lib/systemd/systemd-fsckd
This is the daemon which displays two useless '\r' characters.

I went to:
  http://packages.ubuntu.com/xenial/systemd

I downloaded:
  http://archive.ubuntu.com/ubuntu/pool/main/s/systemd/systemd_229-4ubuntu10.debian.tar.xz

The file debian/patches/fsckd-daemon-for-inter-fsckd-communication.patch
contains:
+static int manager_write_console(Manager *m, const char *message) {
[...]
+ if (message) {
+ fprintf(console, "\r%s\r%n", message, &l);
+ if (m->clear < (size_t)l)
+ m->clear = (size_t)l;
+ } else {
+ fputc('\r', console);
+ for (j = 0; j < m->clear; j++)
+ fputc(' ', console);
+ fputc('\r', console);
+ }

So, when no message was previously displayed, "m->clear" is still set to 0.

Then, when the program ends it calls:
+ /* clear last line */
+ manager_write_console(m, NULL);

However, in the "else" above, two '\r' characters are displayed, surrounding
no space characters.

So, when no message was previously displayed, there is nothing to clear, so
no '\r' character to display.

A trivial patch is attached. It is untested.

[Ubuntu Foundations Team Bug Bot (crichton)]

The attachment "patch_to_remove_useless_cr.patch" seems to be a patch. If it isn't, please remove the "patch" flag from the attachment, remove the "patch" tag, and if you are a member of the ~ubuntu-reviewers, unsubscribe the team.

[This is an automated message performed by a Launchpad user owned by ~brian-murray, for any issues please contact him.]

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Dimitri John Ledkov (xnox)]

Interesting.

[Dimitri John Ledkov (xnox)]

Didrocks, would you be able to review this patch?

[Didier Roche (didrocks)]

Thanks for submitting this patch and sorry for the time to review it!

The patch looks good to me, I would love though to get that directly upstream rather than us carrying a distro-patch for a small issue like this, do you mind doing a PR there? https://github.com/systemd/systemd/

[Laurent (laurent35263)]

Hello,

Thank you for your reply.

Unfortunately, the bug is NOT in upstream systemd, but in a Ubuntu specific patch.

A few things changed since last year:

Systemd version is now 229-4ubuntu21.2.

Its source is now at:
  http://archive.ubuntu.com/ubuntu/pool/main/s/systemd/systemd_229-4ubuntu21.2.debian.tar.xz

The bugged function manager_write_console() is still there inside:
  debian/patches/fsckd-daemon-for-inter-fsckd-communication.patch

The new patch is attached. This patch can be used to patch the Ubuntu specific patch.

Thank you.

[Didier Roche (didrocks)]

Interesting, I was sure we upstreamed completely systemd-fsckd. Anyway, +1 for me, let me assign to xnox who is doing most of systemd uploads nowdays so that he attaches it to next upload.

Many thanks!

[Zhang Youfu (zhangyoufu)]

This bug still exists in 19.04 Disco. Please fix it.