psmask: 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/psmask - from package: GMT

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

On Debian possible default full paths are:

/usr/lib/gmt/bin/psmask - from package: GMT

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

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