Re: Container Uptime Discussion

--000000000000d53dc70610d86781
Content-Type: text/plain; charset="UTF-8"

On Tue, 30 Jan 2024 at 21:36, Dr. Werner Fink <[email protected]> wrote:

>   ps o etimes= 1
>
> to get the uptime of the container in seconds.

 I have effectively written procps_container_uptime() to do that.

Interesting would be if
>
the uptime command would accept an further option to specify the namespace
> pid of the container to do this from outside aka the host system.  This
>
Strangely enough its not the pid namespace that matters. You (and I
originally) would think ok this
is a program about PIDS, pids namespace is what I need. But actually what
you want is the mount
namespace to get to "their" /proc.

"nsenter -t <docker_bash_pid>  -p ps ax" shows all the host processes,
because that's what is in /proc

Anyway, it seems to work.
Starting in the top directory of procps and making sure the container glibc
is the same, or close enough to the host's glibc version.
$ docker run -it --mount type=bind,source="$(pwd)",target=/mnt debian:latest
root@c00eb009173d:/# LD_PRELOAD=/mnt/library/.libs/libproc2.so
/mnt/src/.libs/uptime
 22:19:37 up 5 days, 17:04,  0 users,  load average: 0.30, 0.28, 0.21
root@c00eb009173d:/# LD_PRELOAD=/mnt/library/.libs/libproc2.so
/mnt/src/.libs/uptime --container
 22:19:41 up 0 min,  0 users,  load average: 0.28, 0.27, 0.21
(wait 2 minutes)
root@c00eb009173d:/# LD_PRELOAD=/mnt/library/.libs/libproc2.so
/mnt/src/.libs/uptime --container
 22:21:29 up 2 min,  0 users,  load average: 0.54, 0.38, 0.26

Both w and uptime have this change. I haven't attempted to do any
comparison between variables and uptime
(e.g. vmstat's initial set of numbers) because there doesn't seem to be a
clear way of doing it.

But at least now you can work out from inside the container how long its
been running.
 - Craig

--000000000000d53dc70610d86781
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr"><div dir=3D"ltr">On Tue, 30 Jan 2024 at 21:36, Dr. Werner =
Fink &lt;<a href=3D"mailto:[email protected]" target=3D"_blank">[email protected]=
</a>&gt; wrote:</div><div class=3D"gmail_quote"><blockquote class=3D"gmail_=
quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,=
204);padding-left:1ex">=C2=A0 ps o etimes=3D 1<br>
<br>
to get the uptime of the container in seconds.=C2=A0 </blockquote><div>=C2=
=A0I have effectively written procps_container_uptime() to do that.</div><d=
iv><br></div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px =
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Interesting =
would be if <br></blockquote><blockquote class=3D"gmail_quote" style=3D"mar=
gin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1=
ex">
the uptime command would accept an further option to specify the namespace<=
br>
pid of the container to do this from outside aka the host system.=C2=A0 Thi=
s<br></blockquote><div>Strangely enough its not the pid namespace that matt=
ers. You (and I originally) would think ok this</div><div>is a program abou=
t PIDS, pids namespace is what I need. But actually what you want is the mo=
unt</div><div>namespace to get to &quot;their&quot; /proc.</div><div><br></=
div><div>&quot;nsenter -t &lt;docker_bash_pid&gt;=C2=A0 -p ps ax&quot; show=
s all the host processes, because that&#39;s what is in /proc</div><div><br=
></div><div>Anyway, it seems to work.</div><div>Starting in the top directo=
ry of procps and making sure the container glibc is the same, or close enou=
gh to the host&#39;s glibc version.<br></div><div>$ docker run -it --mount =
type=3Dbind,source=3D&quot;$(pwd)&quot;,target=3D/mnt debian:latest<br>root=
@c00eb009173d:/# LD_PRELOAD=3D/mnt/library/.libs/libproc2.so /mnt/src/.libs=
/uptime<br>=C2=A022:19:37 up 5 days, 17:04, =C2=A00 users, =C2=A0load avera=
ge: 0.30, 0.28, 0.21<br>root@c00eb009173d:/# LD_PRELOAD=3D/mnt/library/.lib=
s/libproc2.so /mnt/src/.libs/uptime --container<br>=C2=A022:19:41 up 0 min,=
 =C2=A00 users, =C2=A0load average: 0.28, 0.27, 0.21</div><div>(wait 2 minu=
tes)</div><div>root@c00eb009173d:/# LD_PRELOAD=3D/mnt/library/.libs/libproc=
2.so /mnt/src/.libs/uptime --container<br>=C2=A022:21:29 up 2 min, =C2=A00 =
users, =C2=A0load average: 0.54, 0.38, 0.26</div><div><br></div><div>Both w=
 and uptime have this change. I haven&#39;t attempted to do any comparison =
between variables and uptime</div><div>(e.g. vmstat&#39;s initial set of nu=
mbers) because there doesn&#39;t seem to be a clear way of doing it.</div><=
div><br></div><div>But at least now you can work out from inside the contai=
ner how long its been running.<br></div><div>=C2=A0- Craig</div><div><br></=
div></div></div>

--000000000000d53dc70610d86781--