qdbusviewer: 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 CentOS possible default full paths are:

/usr/lib64/qt5/bin/qdbusviewer - from package: qt5-qdbusviewer
/usr/bin/qdbusviewer - from package: qt-x11
/usr/lib64/qt4/bin/qdbusviewer - from package: qt-x11
/usr/lib/qt4/bin/qdbusviewer - from package: qt-x11

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/qdbusviewer - from package: qtchooser
/usr/lib/x86_64-linux-gnu/qt4/bin/qdbusviewer - from package: qt4-dev-tools
/usr/lib/x86_64-linux-gnu/qt5/bin/qdbusviewer - from package: qttools5-dev-tools

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

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