col6: 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/col6 - from package: byobu

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

Error in other languages:
col6: bevel nie gevind nie
col6: comandă negăsită
col6: comando não encontrado
col6: commande introuvable
col6: command not found
col6: käsku ei ole
col6: không tìm thấy lệnh
col6: komanda nerasta
col6: Kommando nicht gefunden.
col6: kommandot finns inte
col6: komut yok
col6: nie znaleziono polecenia
col6: níor aimsíodh an t-ordú
col6: no se encontró la orden
col6: no s'ha trobat l'ordre
col6: opdracht niet gevonden
col6: parancs nem található
col6: perintah tidak ditemukan
col6: príkaz nenájdený
col6: příkaz nenalezen
col6: команда не найдена
col6: командата не е открита
col6: 命令找不到
col6: コマンドが見つかりません