convert_sym: 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/convert_sym - from package: geda-utils

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

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