xrdp-sesman: 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/sbin/xrdp-sesman - from package: xrdp

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

On Debian possible default full paths are:

/usr/sbin/xrdp-sesman - from package: xrdp

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

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