marked: 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 CentOS possible default full paths are:

/usr/bin/marked - from package: marked
/usr/lib/node_modules/marked/bin/marked - from package: marked

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/marked - from package: node-marked
/usr/lib/nodejs/marked/bin/marked - from package: node-marked

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

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