gdbserver: 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/gdbserver - from package: gdb-gdbserver

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

On Debian possible default full paths are:

/usr/bin/gdbserver - from package: gdbserver

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

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