extcheck: 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 Debian possible default full paths are:

/usr/lib/debug/usr/lib/jvm/java-7-openjdk-amd64/bin/extcheck - from package: openjdk-7-dbg
/usr/lib/jvm/java-7-openjdk-amd64/bin/extcheck - from package: openjdk-7-jdk

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

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