osmconvert: 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/osmconvert - from package: osmctools

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

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