smbpasswd: 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/smbpasswd - from package: samba4-client
/usr/bin/smbpasswd - from package: samba-common

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

On Debian possible default full paths are:

/usr/bin/smbpasswd - from package: samba-common-bin

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

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