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

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

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