dcraw_emu: 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
/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_emu - from package: LibRaw-samples

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