xrdp-sesadmin: 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/xrdp-sesadmin - from package: xrdp

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

On Debian possible default full paths are:

/usr/bin/xrdp-sesadmin - from package: xrdp

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

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