haddock-ghc-7.6.3: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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/haddock-ghc-7.6.3 - from package: ghc
/usr/lib/ghc/bin/haddock-ghc-7.6.3 - from package: ghc

You may install the required package with command apt-get install {package}
Error in other languages:
haddock-ghc-7.6.3: bevel nie gevind nie
haddock-ghc-7.6.3: comandă negăsită
haddock-ghc-7.6.3: comando não encontrado
haddock-ghc-7.6.3: commande introuvable
haddock-ghc-7.6.3: command not found
haddock-ghc-7.6.3: käsku ei ole
haddock-ghc-7.6.3: không tìm thấy lệnh
haddock-ghc-7.6.3: komanda nerasta
haddock-ghc-7.6.3: Kommando nicht gefunden.
haddock-ghc-7.6.3: kommandot finns inte
haddock-ghc-7.6.3: komut yok
haddock-ghc-7.6.3: nie znaleziono polecenia
haddock-ghc-7.6.3: níor aimsíodh an t-ordú
haddock-ghc-7.6.3: no se encontró la orden
haddock-ghc-7.6.3: no s'ha trobat l'ordre
haddock-ghc-7.6.3: opdracht niet gevonden
haddock-ghc-7.6.3: parancs nem található
haddock-ghc-7.6.3: perintah tidak ditemukan
haddock-ghc-7.6.3: príkaz nenájdený
haddock-ghc-7.6.3: příkaz nenalezen
haddock-ghc-7.6.3: команда не найдена
haddock-ghc-7.6.3: командата не е открита
haddock-ghc-7.6.3: 命令找不到
haddock-ghc-7.6.3: コマンドが見つかりません