ddrescuelog: 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/ddrescuelog - from package: ddrescue

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

On Debian possible default full paths are:

/usr/bin/ddrescuelog - from package: gddrescue

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

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