mktorrent: 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/mktorrent - from package: mktorrent

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

On Debian possible default full paths are:

/usr/bin/mktorrent - from package: mktorrent

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

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