expect_mkpasswd: 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_mkpasswd - from package: expect

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