convertall: 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/convertall - from package: convertall

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