petscarch.1.gz: 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 Debian possible default full paths are:

/usr/lib/petscdir/3.4.2/bin/petscarch.1.gz - from package: libpetsc3.4.2-dev

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

Error in other languages:
petscarch.1.gz: bevel nie gevind nie
petscarch.1.gz: comandă negăsită
petscarch.1.gz: comando não encontrado
petscarch.1.gz: commande introuvable
petscarch.1.gz: command not found
petscarch.1.gz: käsku ei ole
petscarch.1.gz: không tìm thấy lệnh
petscarch.1.gz: komanda nerasta
petscarch.1.gz: Kommando nicht gefunden.
petscarch.1.gz: kommandot finns inte
petscarch.1.gz: komut yok
petscarch.1.gz: nie znaleziono polecenia
petscarch.1.gz: níor aimsíodh an t-ordú
petscarch.1.gz: no se encontró la orden
petscarch.1.gz: no s'ha trobat l'ordre
petscarch.1.gz: opdracht niet gevonden
petscarch.1.gz: parancs nem található
petscarch.1.gz: perintah tidak ditemukan
petscarch.1.gz: príkaz nenájdený
petscarch.1.gz: příkaz nenalezen
petscarch.1.gz: команда не найдена
petscarch.1.gz: командата не е открита
petscarch.1.gz: 命令找不到
petscarch.1.gz: コマンドが見つかりません