xcalib: 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/xcalib - from package: xcalib

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

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