This guide will assist in setting up a Valheim Dedicated Server (VHDS)
on Slackware64-current. This procedure should also work on Slackware6-14.2,
although additional prerequisites may be required. The process is similar
to setting up a Half-Life Dedicated Server (HLDS) with one important
simplification. We will be using LinuxGSM: the Linux Game Server Manager.

LinuxGSM is a command line tools written in BASH to greatly simplify and
streamline the installation of Linux dedicated game servers. The
instructions are easy and straightforward.

Prerequisites
---------------

    Slackware64 multilib
    steamCMD (32-bit only)
    LinuxGSM (bash) [NOTE: LinuxGSM will install steamCMD.]


The VHDS is x86_64 while SteamCMD is 32-bit. Thus, we need to convert
Slackware64 to Slackware64-multilib. Instructions for doing so are
described in "Adding Multilib Capability to Slackware on x86_64
Architecture". If you've set up the Steam Client on Slackware64, then
you are familiar with this process.

As the 'root' user, you first create a dedicated user account under which SteamCMD ann VHDS will run.

# groupadd steam
# useradd -g steam -m -d /home/steam -c "Steam server account" -s /bin/bash steam

Then set a password for the new âsteamâ account:

# passwd steam

For convenience, symlink 'ip' and 'ethtool' so that the steam user can
access these tools, since we are not going to use 'sudo', and to squash
the resulting errors and warnings. For some reason the LinuxGSM scripts
to not use the full file path which would make this step necessary. I
might submit a bug/feature request about this.

# ln -s /sbin/ip /bin/ip
# ln -s /usr/sbin/ethtool /usr/bin/ethtool

Valheim server uses anonymous login. Other servers will prompt for a Steam
login. You can create a new Steam user dedicated to running servers.
Recommended. Do not use your current Steam Client login. You can place
the Steam login credentials into
$HOME/lgsm/config-lgsm/<servername>/secrets-{common|<servername>}.cfg
but note that these credentials are stored in plain text.

## SteamCMD Login
steamuser="username"
steampass="password"

Now we are ready to Install LinuxGSM. This will install SteamCMD
automatically as needed. Login as our 'steam' user, and download LinuxGSM,
and install:

$ cd $HOME
$ wget -O linuxgsm.sh https://linuxgsm.sh
$ chmod +x linuxgsm.sh

You can get a list of all available servers with:

$ ./linuxgsm.sh list

Now to install out Valheim server:

$ ./linuxgsm.sh vhserver
$ ./vhserver install

Now you have the file tree in your 'steam' user home directory, as well
as a '.steam' for the SteamCMD files.

Next, You'll want to adjust the default configuration to set up the server
parameters. '~/lgsm/config-default/config-lgsm/' contains the default and
example configurations. Leave the _default.cfg alone as they will be
overwritten on updates. Each lower layer overrides the previous one. This
is so that you can set up multiple independent servers.

In the '~/lgsm/config/lgsm/vhserver' directory, copy _default.cfg to
common.cfg and customize as needed. Since we are running just one Valheim
server, we can stuff everyting into common.cfg. Whan runnign multiple
servers, the common parameters are here, and parameters specific to each
server is on secrets-<server name>.cfg and <server name>.cfg. Set up the
server parameters (customize as needed):

#### Game Server Settings ####

## Predefined Parameters | https://docs.linuxgsm.com/configuration/start-parameters
servername="<Server name>"
serverpassword="<server password>"
port="2456"
gameworld="${selfname}"
public="1"
ip=<server local LAN IP>

The rest you can leave at the defaults, or customize as needed.

I recommend setting the PC running the server to a fixed IP on your home
network. Port=2456 (UDP) is the default; change as needed. Next, open
your router's firewall or use port forwarding for port range 2456-2458 (UDP).
Note that the port specified in the configuration is the start of a port
triplet. When connecting via the Steam client, the Valheim in game community
browser can be a bit finicky. You can explicitly set the server IP via the
Steam Client View -> Servers -> Favorites -> Add a Server and enter the
<server IP>:<port+1>

NOTE: This is the external, or direct, IP from your internet service
provider. This will not necessarily be the IP in config.cfg if you are
behind a router/cable modem etc.

[Update: The in-game server browser has improved a bit, but can still
take some time to find your server. There is now a button for direct IP
entry.]

Now run the server:

$ ./vhserver start

Just running 'vhserver' will provide a list of commands. View server
information with:

$ ./vhserver details

This will provide your external IP. A number of server commands are
available (see References). Valheim specific information is located:
~/serverfiles/Valheim Dedicated Server Manual.pdf

References:
---------------
https://linuxgsm.com
https://docs.linuxgsm.com/
https://docs.linuxgsm.com/steamcmd
https://linuxgsm.com/lgsm/vhserver/
https://docs.linuxgsm.com/commands
https://docs.slackware.com/howtos:games:halflife_dedicated_server
https://developer.valvesoftware.com/wiki/SteamCMD