Kiwi NG hangs on RPM installation that is using /dev/urandom

[sebastiaan...@gmail.com]

Hi,

I'm facing a weird issue with building a SLES 15 SP5 VMX flavour. The build process just hangs on installing my own compiled freeradius RPM:

[ DEBUG   ]: 10:42:09 | system: (492/530) Installing: freeradius-server-3.2.6-150500.155.199.1.NIVO.SLES15.x86_64

The same RPM installs fine when the VM is build without this RPM and installing it after first boot. Further investigation shows me that Kiwi hangs on my %post section inside the RPM. The Kiwi process causes high load on running:

root     26287 96.3  0.0   2564   712 pts/0    R    10:42   4:33          \_ tr -cd [:alnum:]

My relevant part of the RPM %post section:

PASSWD=$(tr -cd '[:alnum:]' < /dev/urandom | fold -w16 | head -n1)

Are there any known problem with using urandom inside the chroot? Or has this something to do with the subshell? I'm using KIWI (next generation) version 9.25.22.

Thanks!

Sebastiaan

[Marcus Schäfer]

Hi,

> PASSWD=$(tr -cd '[:alnum:]' < /dev/urandom | fold -w16 | head -n1)
>
> Are there any known problem with using urandom inside the chroot? Or
> has this something to do with the subshell? I'm using KIWI (next
> generation) version 9.25.22.

Hmm, not to my knowledge

Does it behave differently if you put the package into the bootstrap
section of your image description ?

<packages type="bootstrap">
<package name="freeradius-server"/>
<... the other bootstrap stuff ...
</packages>

The bootstrap installaton process is no chroot process,
just to double check if that makes any difference

Regards,
Marcus
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[Sebastiaan Veldhuisen]

Hi Marcus,

Let me check whether I see the same behaviour when specifying the RPM inside the bootstrap section. It is really strange: the bash line generating a random password eats up a single CPU. Kiwi waits on the process to be finished. When doing a hard kill (-9) on the "tr" process, Kiwi continues and the build succeeds (except for the freeradius-server RPM installation ofcourse).

Thanks!

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[Sebastiaan Veldhuisen]

We did a test by placing "freeradius-server" inside the bootstrap section: the result is the same.

[Marcus Schäfer]

Hi,

> We did a test by placing "freeradius-server" inside the bootstrap
> section: the result is the same.

ok, so no chroot issue. In this case I think you run out of entropy
and that makes the read to block.

I did a very quick search on hanging shells when reading from
urandom. Maybe the information from here helps:

https://stackoverflow.com/questions/29493229/why-cat-dev-urandom-hung-my-bash-script

Other than that there is really little from the kiwi side
that we can do here

[Sebastiaan Veldhuisen]

Hi Marcus,

Thanks. I did not known about the bad practice to cat /dev/urandom. I guess I have learned something new today. If somebody else has the same problem:

dd bs=16 count=1 if=/dev/urandom | base64 | tr +/ _.

Works fine!

Thanks for your expertise!

kind regards,

Sebastiaan

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