gdbtui: 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/gdbtui - from package: gdb

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

On Debian possible default full paths are:

/usr/bin/gdbtui - from package: gdb

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

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