preconv: 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/preconv - from package: groff-base

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

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