ocamltags: 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/ocamltags - from package: ocaml-emacs

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

On Debian possible default full paths are:

/usr/bin/ocamltags - from package: ocaml-mode

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

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