cat: 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:

/bin/cat - from package: coreutils

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

On Debian possible default full paths are:

/bin/cat - from package: coreutils
/usr/lib/plan9/bin/cat - from package: 9base
/usr/lib/klibc/bin/cat - from package: klibc-utils

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

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