checklink: 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/checklink - from package: w3c-linkchecker

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

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