thin_rmap: 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:

/sbin/thin_rmap - from package: device-mapper-persistent-data
/usr/sbin/thin_rmap - from package: device-mapper-persistent-data

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

On Debian possible default full paths are:

/usr/sbin/thin_rmap - from package: thin-provisioning-tools

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

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