dcraw_half: 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 CentOS possible default full paths are:

/usr/bin/dcraw_half - from package: LibRaw-samples

You may install the required package with command yum install {package}

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