thin_trim: 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_trim - from package: device-mapper-persistent-data
/usr/sbin/thin_trim - from package: device-mapper-persistent-data

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

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