schdiff: 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/schdiff - from package: geda-utils

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

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