gkeytool: 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/gkeytool - from package: libgcj

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

On Debian possible default full paths are:

/usr/bin/gkeytool - from package: gcj-jre-headless

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

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