session-cleaner: 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/lib/wims/bin/session-cleaner - from package: wims

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

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