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List:       coreutils-bug
Subject:    bug#21349: who shows no users (looking in wrong place)
From:       "L. A. Walsh" <coreutils () tlinx ! org>
Date:       2015-12-29 23:21:18
Message-ID: 5683156E.7060907 () tlinx ! org
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L. A. Walsh wrote:
> Erik Auerswald wrote:
>>
>> Linda A. Walsh noticed a similar thing:
>>  
>>> The same thing happens on openSuSE
>>>     
> ----
>
> Looked into this a bit more and found that while
> 'w' and 'who' didn't work, "last" did.
>
> Tracked it down to this...
> from the linux programmer's manual UTMP(5)
>
> it says conforming implementations should look in:
> FILES
>       /var/run/utmp
>       /var/log/wtmp
> --------------
>
> tracing who (I assume 'w' uses similar code):
> # strace who|& grep /var
> access("/var/run/utmpx", F_OK)          = -1 ENOENT (No such file or 
> directory)
> open("/var/run/utmp", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or 
> directory)
> access("/var/run/utmpx", F_OK)          = -1 ENOENT (No such file or 
> directory)
> open("/var/run/utmp", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or 
> directory)
> ----
>
> I.e. it isn't checking the 2nd location.
>
> Adding a link in the *ephemeral* (tmpfs/ramdisk) /var/run allows
> it to temporarily work:
>
> # ln -s ../log/wtmp utmp
>
>>  who
> law      pts/0        2015-11-29 09:49 (athenae)
> root     tty1         2015-12-22 09:26
> law      pts/1        2015-12-23 16:57 (athenae)
> law      pts/0        2015-12-25 17:46 (athenae)
> law      pts/2        2015-12-25 21:42 (athenae)
> law      pts/4        2015-12-25 22:23 (athenae)
> law      pts/5        2015-12-27 08:46 (athenae)
> law      pts/6        2015-12-27 12:54 (athenae)
> law      pts/7        2015-12-27 12:59 (athenae)
>>  w
> 13:18:22 up 108 days, 21:03, 459 users,  load average: 1.33, 1.25, 0.99
> USER     TTY      FROM             LOGIN@   IDLE   JCPU   PCPU WHAT
> law      pts/0    athenae          29Nov15 39:52m  6:38   1.18s 
> dovecot/imap [l
> root     tty1                      Tue09    3days  0.28s  0.28s -bash
> law      pts/1    athenae          Wed16    2days  0.30s  0.30s -bash
> law      pts/0    athenae          Fri17   39:52m  6:38   1.11s -bash
> law      pts/2    athenae          Fri21   37:18m  0.42s  0.42s -bash
> law      pts/4    athenae          Fri22   38:52m  0.25s  0.25s -bash
> law      pts/5    athenae          08:46    1:39m  0.57s  0.57s -bash
> law      pts/6    athenae          12:54   12:44   0.37s  0.37s -bash
> law      pts/7    athenae          12:59    0.00s  0.29s  0.01s w
>>  last|grep 'still log'
> law      pts/7        athenae          Sun Dec 27 12:59   still logged 
> in  law      pts/6        athenae          Sun Dec 27 12:54   still 
> logged in  law      pts/5        athenae          Sun Dec 27 08:46   
> still logged in  law      pts/4        athenae          Fri Dec 25 
> 22:23   still logged in  law      pts/2        athenae          Fri 
> Dec 25 21:42   still logged in  law      pts/0        athenae          
> Fri Dec 25 17:46   still logged in  law      pts/1        
> athenae          Wed Dec 23 16:57   still logged in  root     
> tty1                          Tue Dec 22 09:26   still logged in
>
> ----------------------------------------------
>
> While creating a symlink in /var/run/utmp => /var/log/wtmp
> is a per-boot, workaround to get this to work until 'w/who' are fixed,
> both of them should check the linux-standard locations documented
> in the manpage.
>
> Likely /var/log is a new location (as /var/run was made ephemeral
> as part of the transition to systemd).  Note, there was some
> pressure by the systemd folks to also make /var/log ephemeral
> as well as /tmp and /var/tmp, but those were resisted, at least
> in "SUSE"...(at least for now...), since the default for systemd
> is to not store or save logfiles (or coredumps) over boots.
>
> One can tell from design choices like that systemd is designed for
> end-consumer systems, where logs that document things might
> be inconvenient (vs. any publicly owned corporation, law group
> bank or medical office where retaining logs for some period
> of time is required by US law).
>
>
>



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