fuser: 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:

/sbin/fuser - from package: psmisc

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

On Debian possible default full paths are:

/bin/fuser - from package: psmisc

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

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