sketch: 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/sketch - from package: sketch

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

On Debian possible default full paths are:

/usr/bin/sketch - from package: sketch

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

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