checkint: 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/checkint - from package: netdiag

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

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