dbus-monitor: 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:

/bin/dbus-monitor - from package: dbus

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

On Debian possible default full paths are:

/usr/lib/x86_64-linux-gnu/dbus-1.0/debug-build/bin/dbus-monitor - from package: dbus-1-dbg
/usr/bin/dbus-monitor - from package: dbus

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

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