ftstring: 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/ftstring - from package: freetype-demos

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

On Debian possible default full paths are:

/usr/bin/ftstring - from package: freetype2-demos

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

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