skel: 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:

/sbin/skel - from package: nut

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

On Debian possible default full paths are:

/usr/bin/skel - from package: libadios-bin

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

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