ui: 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 Debian possible default full paths are:

/usr/bin/ui - from package: userinfo

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

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