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I have a statically linked busybox and want to be able to write busybox telnet foo. How do I specify the address of "foo"?

Do I really need /etc/nsswitch.conf and the corresponding dynamic libraries, or does busybox contain some own simple mechanism to consult /etc/hosts?

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    As Rui writes, this depends on the libc. What libc was this busybox compiled against? And with what configuration was busybox compiled? Also, how are you getting DNS? For example *wrt systems typically run dnsmasq and have a static host list that dnsmasq reads and serves via DNS. – Gilles Apr 25 '16 at 22:10
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Looking into my openWRT, I do not have any libnss* libraries installed. It seems that only libuClibc is used for that. libc.so.0 is a symlink to it.

root@RuiWifi:/lib# grep -ri hosts *
libc.so.0:/etc/hosts
libuClibc-0.9.33.2.so:/etc/hosts

uClibc is an implementation of the standard C library that is much smaller than glibc, which makes it useful for embedded systems.

If you are trying to put together a minimal environment, I would advise you to compile busybox against UClibc instead of glibc, and snooping around openWRT to see how they managed to put together such a distribution with such a small footprint.

Compiling BusyBox with uClibc

  • In your case busybox seems to be dynamically linked. If I understand correctly uClibc looks directly at /etc/hosts, but my busybox seems not to care about the content of that file. – michas Apr 25 '16 at 7:48
  • I assumed initially you were into one of the ...wrt systems, and then it just clicked me you only mentioned a compiled busybox, hence my last paragraph and edit. – Rui F Ribeiro Apr 25 '16 at 7:49
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See dnsd which can be built into Busybox:

root@alpine-linux [~]# ls -l $(which dnsd)
lrwxrwxrwx    1 root  root  12 Mar 17 23:12 /usr/sbin/dnsd -> /bin/busybox

configuring dnsd

I was also able configure unbound to provide name resolution for .local domains in Alpine Linux (which also uses Busybox).

See local-data in the unbound.conf man page. By default it is commented out of the config file.

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