ctags-exuberant: 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/ctags-exuberant - from package: exuberant-ctags

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

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