Questions about last command output

linuxfia · 10-14-2008, 01:43 PM

hello

When I do a last grep on user jdoe, I get:
jdoe pts/1 localhost Mon Aug 2 10:20 - 10:20 (00:00)
jdoe sshd localhost Mon Aug 2 10:20 - 10:20 (00:00)
jdoe pts/6 67.16.1.10.trm0 Mon Aug 2 10:14 - 10:20 (00:05)
jdoe sshd 67.16.1.10.trm0 Mon Aug 2 10:14 - 10:20 (00:05)

It seems the bottom 2 lines show the IP address where the connection was made from.

The top 2 lines says "localhost". What does that mean? It's not saying it logged on locally to the console right?

indienick · 10-14-2008, 01:47 PM

It most certainly is saying that the user, "jdoe", had logged on locally.

linuxfia · 10-14-2008, 04:38 PM

It doesn't mean the user logged on from the physical console right?
Would ssh'ing into the server remotely produce the same log?

This is the other part of the log:

Accepted keyboard-interactive for jdoe from 67.16.1.10 port 50752 ssh2
messages.005:Aug 2 10:20:20 server.domain.com sshd[29202]: [ID 900126 auth.info] Accepted keyboard-interactive for jdoe from 127.0.0.1 port 57521 ssh2

indienick · 10-14-2008, 09:10 PM

To be honest, I do not know.

gilead · 10-14-2008, 09:32 PM

When I log in locally to my boxes (Slackware) I get tty1 (or whatever tty it was) and the host field is empty. If I use last -a -d I get 0.0.0.0 for the host.

The only time I see values like 127.0.0.1 for the connecting host when I'm not actually locally signing in is when I use NX over an SSH tunnel. In that case, I get an entry for last showing my remote IP addres as I'd expect, but in /var/log/messages I get something like this:

Code:

Oct 13 08:36:36 zaphod sshd[24561]: Accepted publickey for nx from 127.0.0.1 port 42308 ssh2

Were you running any programs over an SSH tunnel when those entries occurred?

linuxfia · 10-15-2008, 11:28 AM

I'm not sure since that wasn't me but another user...
When I do last, other users don't have an entry of localhost but only that particular user does.
When you do NX over ssh, does it log as "localhost" when using last command and in var/log/messages as 127.0.0.1?

gilead · 10-15-2008, 08:01 PM

I went back and matched up time stamps from remotely connecting via SSH and using NX with the output from last. There are no localhost messages as you describe. I also haven't been able to force a hostname of localhost by connecting locally.

It could be differences in the versions of utilities between Ubuntu and Slackware unless someone else has jdoe's credentials and may have used them locally. That doesn't seem likely given that the timestamps follow on from each other.

linuxfia · 10-17-2008, 04:33 PM

Ok, thanks for your help!

linuxfia · 10-23-2008, 06:35 PM

So how do I delete the lastlog?

gilead · 10-23-2008, 10:37 PM

Do you mean truncate it or remove it entirely? To truncate it, you can use the following - I'd use lsof first to see if anything is using the file:

Code:

lsof /var/log/lastlog
:>/var/log/lastlog

linuxfia · 10-24-2008, 11:16 AM

I meant to clear all of it so when I run "last", nothing shows up.
Thanks.

linuxfia · 10-30-2008, 12:03 PM

Anyone know the command to to clear all of it so when I run the "last" command, nothing shows up?

gilead · 10-30-2008, 01:20 PM

Sorry, I listed the wrong filename before. last uses /var/log/wtmp, so to truncate it:

Code:

:>/var/log/wtmp

You should also be able to move it to another file (e.g. /var/log/wtmp.1 like logrotate does) and create a new, empty file with touch.

linuxfia · 10-31-2008, 02:53 PM

Cool, thanks!