gjarsigner: 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/gjarsigner - from package: libgcj

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

On Debian possible default full paths are:

/usr/bin/gjarsigner - from package: gcj-jdk

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

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