jail_uml: 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/sbin/jail_uml - from package: uml_utilities

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

On Debian possible default full paths are:

/usr/sbin/jail_uml - from package: uml-utilities

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

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