gdb-add-index: 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/gdb-add-index - from package: gdb

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

On Debian possible default full paths are:

/usr/bin/gdb-add-index - from package: gdb

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

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