ksudoku: 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/ksudoku - from package: kdegames

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

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