ktorrent: 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/ktorrent - from package: ktorrent

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

On Debian possible default full paths are:

/usr/bin/ktorrent - from package: ktorrent

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

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