gtk-update-icon-cache-3.0: 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 Debian possible default full paths are:

/usr/bin/gtk-update-icon-cache-3.0 - from package: libgtk-3-bin

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

Error in other languages:
gtk-update-icon-cache-3.0: bevel nie gevind nie
gtk-update-icon-cache-3.0: comandă negăsită
gtk-update-icon-cache-3.0: comando não encontrado
gtk-update-icon-cache-3.0: commande introuvable
gtk-update-icon-cache-3.0: command not found
gtk-update-icon-cache-3.0: käsku ei ole
gtk-update-icon-cache-3.0: không tìm thấy lệnh
gtk-update-icon-cache-3.0: komanda nerasta
gtk-update-icon-cache-3.0: Kommando nicht gefunden.
gtk-update-icon-cache-3.0: kommandot finns inte
gtk-update-icon-cache-3.0: komut yok
gtk-update-icon-cache-3.0: nie znaleziono polecenia
gtk-update-icon-cache-3.0: níor aimsíodh an t-ordú
gtk-update-icon-cache-3.0: no se encontró la orden
gtk-update-icon-cache-3.0: no s'ha trobat l'ordre
gtk-update-icon-cache-3.0: opdracht niet gevonden
gtk-update-icon-cache-3.0: parancs nem található
gtk-update-icon-cache-3.0: perintah tidak ditemukan
gtk-update-icon-cache-3.0: príkaz nenájdený
gtk-update-icon-cache-3.0: příkaz nenalezen
gtk-update-icon-cache-3.0: команда не найдена
gtk-update-icon-cache-3.0: командата не е открита
gtk-update-icon-cache-3.0: 命令找不到
gtk-update-icon-cache-3.0: コマンドが見つかりません