thunar-volman: 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/thunar-volman - from package: thunar-volman

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

On Debian possible default full paths are:

/usr/bin/thunar-volman - from package: thunar-volman

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

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