[Bug 1563025] Re: 'last' command output is wrong

[Richard Hickling]

Hey, I'm not sure if this is a general fix, but it fixes for me locally:

--- a/login-utils/last.c	(revision before change)
+++ b/login-utils/last.c	(revision with change)
@@ process_wtmp_file(...) switch statement:
-		case BOOT_TIME:
-			strcpy(ut.ut_line, "system boot");
-			quit = list(ctl, &ut, lastdown, R_REBOOT);
-			lastboot = ut.ut_tv.tv_sec;
-			down = 1;
-			break;
+		case BOOT_TIME:
+			strcpy(ut.ut_line, "system boot");
+			/* If this boot record is older than a later boot event and no shutdown time has yet been recorded,
+			   skip printing it so that it doesn't erroneously show "still running". */
+			if (lastboot != 0 && ut.ut_tv.tv_sec < lastboot && lastdown == currentdate)
+				break;
+			quit = list(ctl, &ut, lastdown, R_REBOOT);
+			lastboot = ut.ut_tv.tv_sec;
+			down = 1;
+			break;

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https://bugs.launchpad.net/bugs/1563025

Title:
  'last' command output is wrong

Status in util-linux package in Ubuntu:
  Confirmed

Bug description:
  Xubuntu 15.10
  util-linux 2.26.2-6ubuntu3

  The output of 'last reboot' is wrong. It says 'reboot' is 'still
  running' when it shouldn't be, and then arbitrarily 'reboot' stops
  running, causing strange lines such as:

  reboot   system boot  4.2.0-30-generic Tue Mar 22 21:25 - 22:59
  (2+01:33)

  This line shows that 'reboot' was logged in from 9:25pm to 10:59pm on
  the same day, but the total login time was 2 days, 1 hour and 33
  minutes.

  'reboot' can be 'still running' multiple times simultaneously.

  I've attached the results of these commands:

  last reboot
  last -f /var/log/wtmp.1 reboot
  last
  last -f /var/log/wtmp.1

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