update-gtk-immodules: 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/update-gtk-immodules - from package: gtk2

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

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