crossfire-server: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/sbin/crossfire-server - from package: crossfire-server

You may install the required package with command apt-get install {package}

Error in other languages:
crossfire-server: bevel nie gevind nie
crossfire-server: comandă negăsită
crossfire-server: comando não encontrado
crossfire-server: commande introuvable
crossfire-server: command not found
crossfire-server: käsku ei ole
crossfire-server: không tìm thấy lệnh
crossfire-server: komanda nerasta
crossfire-server: Kommando nicht gefunden.
crossfire-server: kommandot finns inte
crossfire-server: komut yok
crossfire-server: nie znaleziono polecenia
crossfire-server: níor aimsíodh an t-ordú
crossfire-server: no se encontró la orden
crossfire-server: no s'ha trobat l'ordre
crossfire-server: opdracht niet gevonden
crossfire-server: parancs nem található
crossfire-server: perintah tidak ditemukan
crossfire-server: príkaz nenájdený
crossfire-server: příkaz nenalezen
crossfire-server: команда не найдена
crossfire-server: командата не е открита
crossfire-server: 命令找不到
crossfire-server: コマンドが見つかりません