update-icon-caches: 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/sbin/update-icon-caches - from package: libgtk2.0-bin
/usr/sbin/update-icon-caches - from package: libgtk-3-bin

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

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