usermount: 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/usermount - from package: usermode-gtk

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

On Debian possible default full paths are:

/usr/bin/usermount - from package: usermode

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

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