tuxpaint: 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/tuxpaint - from package: tuxpaint

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

On Debian possible default full paths are:

/usr/bin/tuxpaint - from package: tuxpaint

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

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