tkstool: 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/tkstool - from package: pki-native-tools

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

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