htsserver: 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/htsserver - from package: httrack

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

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