jv-convert: 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/jv-convert - from package: libgcj

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

On Debian possible default full paths are:

/usr/bin/jv-convert - from package: gcj-jdk

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

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