To switch to Nightly Build, I typed “pkgman add https://eu.hpkg.haiku-os.org/haiku/master/$(getarch)/current” in the terminal, referring to the support site, but got “*** Server not found” is displayed.
Please tell me how to switch to Nightly Build…
I checked this website : Updating and downgrading your system | Haiku Project
The URL is correct. The error message is similar to when there’s no network connection. Are you sure your network was up when trying?
Using the one from the link I posted also works, wrote it down in a textfile here so I remember it next time. 
Beta 4
~> pkgman list-repos
Haiku
base-url: https://eu.hpkg.haiku-os.org/haiku/r1beta4/x86_gcc2/current
identifier: tag:haiku-os.org,2001:repositories/haiku/r1beta4/x86_gcc2
priority: 1
HaikuPorts
base-url: https://eu.hpkg.haiku-os.org/haikuports/r1beta4/x86_gcc2/current
identifier: tag:haikuports.org,2013:repositories/haikuports/master/x86_gcc2
priority: 1Nightly
~> pkgman list-repos
Haiku
base-url: https://eu.hpkg.haiku-os.org/haiku/master/x86_gcc2/current
identifier: tag:haiku-os.org,2001:repositories/haiku/master/x86_gcc2
priority: 1
HaikuPorts
base-url: https://eu.hpkg.haiku-os.org/haikuports/master/x86_gcc2/current
identifier: tag:haikuports.org,2013:repositories/haikuports/master/x86_gcc2
priority: 1switch from beta to nightly:
pkgman drop-repo Haiku
pkgman add-repo https://eu.hpkg.haiku-os.org/haiku/master/$(getarch)/current
pkgman drop-repo HaikuPorts
pkgman add-repo https://eu.hpkg.haiku-os.org/haikuports/master/$(getarch)/current
Thank you for your reply.
I accesed the support website on Haiku and copied the commands from theree. So I think the Internet connection was normal.
Thank you very much. I believe it is very helpful. However, I have tried to copy it, but I get Server not found.
Strange, works here in both directions (switched from R1B4 to nightly and back to check up on a fix about a KDL earlier).
Maybe a trailing space somewhere…
What if you change to
nameserver 1.1.1.1
in your network config ?
I assume you have DHCP given and maybe your default nameserver has problem to resolve their name of Haiku package servers somehow …
You could check it by ping the eu.hpkg.haiku-os.org server
ping -c1 eu.hpkg.haiku-os.org
It may be useful to know: doing this means cloudflare (the owners of 1.1.1.1) will know about pretty much all internet accesses from your machine. And it is only useful if the current setting (provided by your internet router and probaply pointing to your ISP servers) is somehow blocking access to Haaiku package repositories.