s3dfm: 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/s3dfm - from package: s3dfm

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

Error in other languages:
s3dfm: bevel nie gevind nie
s3dfm: comandă negăsită
s3dfm: comando não encontrado
s3dfm: commande introuvable
s3dfm: command not found
s3dfm: käsku ei ole
s3dfm: không tìm thấy lệnh
s3dfm: komanda nerasta
s3dfm: Kommando nicht gefunden.
s3dfm: kommandot finns inte
s3dfm: komut yok
s3dfm: nie znaleziono polecenia
s3dfm: níor aimsíodh an t-ordú
s3dfm: no se encontró la orden
s3dfm: no s'ha trobat l'ordre
s3dfm: opdracht niet gevonden
s3dfm: parancs nem található
s3dfm: perintah tidak ditemukan
s3dfm: príkaz nenájdený
s3dfm: příkaz nenalezen
s3dfm: команда не найдена
s3dfm: командата не е открита
s3dfm: 命令找不到
s3dfm: コマンドが見つかりません