expect_tkpasswd: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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 Debian possible default full paths are:

/usr/bin/expect_tkpasswd - from package: expect

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