xml2yaml: 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/bin/xml2yaml - from package: libxml-compile-perl

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

Error in other languages:
xml2yaml: bevel nie gevind nie
xml2yaml: comandă negăsită
xml2yaml: comando não encontrado
xml2yaml: commande introuvable
xml2yaml: command not found
xml2yaml: käsku ei ole
xml2yaml: không tìm thấy lệnh
xml2yaml: komanda nerasta
xml2yaml: Kommando nicht gefunden.
xml2yaml: kommandot finns inte
xml2yaml: komut yok
xml2yaml: nie znaleziono polecenia
xml2yaml: níor aimsíodh an t-ordú
xml2yaml: no se encontró la orden
xml2yaml: no s'ha trobat l'ordre
xml2yaml: opdracht niet gevonden
xml2yaml: parancs nem található
xml2yaml: perintah tidak ditemukan
xml2yaml: príkaz nenájdený
xml2yaml: příkaz nenalezen
xml2yaml: команда не найдена
xml2yaml: командата не е открита
xml2yaml: 命令找不到
xml2yaml: コマンドが見つかりません