gnome-gen-mimedb: 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/gnome-gen-mimedb - from package: gnome-libs

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

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