pstack: 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/pstack - from package: gdb

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

On Debian possible default full paths are:

/usr/bin/pstack - from package: pstack

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

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