xscanimage: 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

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/xscanimage - from package: sane

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