jfs_mkfs: 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/jfs_mkfs - from package: jfsutils

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

On Debian possible default full paths are:

/sbin/jfs_mkfs - from package: jfsutils

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

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