fusioninventory-inventory: 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/bin/fusioninventory-inventory - from package: fusioninventory-agent-task-inventory

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

On Debian possible default full paths are:

/usr/bin/fusioninventory-inventory - from package: fusioninventory-agent

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

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