volumeicon: command not found

Have You tried accessing the binary with the full path?

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/volumeicon - from package: volumeicon-alsa

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