umount.ecryptfs: 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/umount.ecryptfs - from package: ecryptfs-utils

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

On Debian possible default full paths are:

/sbin/umount.ecryptfs - from package: ecryptfs-utils

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

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