upper-covers: 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/upper-covers - from package: ladr4-apps

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

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