ldmd2: 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/ldmd2 - from package: ldc

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

Error in other languages:
ldmd2: bevel nie gevind nie
ldmd2: comandă negăsită
ldmd2: comando não encontrado
ldmd2: commande introuvable
ldmd2: command not found
ldmd2: käsku ei ole
ldmd2: không tìm thấy lệnh
ldmd2: komanda nerasta
ldmd2: Kommando nicht gefunden.
ldmd2: kommandot finns inte
ldmd2: komut yok
ldmd2: nie znaleziono polecenia
ldmd2: níor aimsíodh an t-ordú
ldmd2: no se encontró la orden
ldmd2: no s'ha trobat l'ordre
ldmd2: opdracht niet gevonden
ldmd2: parancs nem található
ldmd2: perintah tidak ditemukan
ldmd2: príkaz nenájdený
ldmd2: příkaz nenalezen
ldmd2: команда не найдена
ldmd2: командата не е открита
ldmd2: 命令找不到
ldmd2: コマンドが見つかりません