rcexplain.2: 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/bin/rcexplain.2 - from package: sra-toolkit

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

Error in other languages:
rcexplain.2: bevel nie gevind nie
rcexplain.2: comandă negăsită
rcexplain.2: comando não encontrado
rcexplain.2: commande introuvable
rcexplain.2: command not found
rcexplain.2: käsku ei ole
rcexplain.2: không tìm thấy lệnh
rcexplain.2: komanda nerasta
rcexplain.2: Kommando nicht gefunden.
rcexplain.2: kommandot finns inte
rcexplain.2: komut yok
rcexplain.2: nie znaleziono polecenia
rcexplain.2: níor aimsíodh an t-ordú
rcexplain.2: no se encontró la orden
rcexplain.2: no s'ha trobat l'ordre
rcexplain.2: opdracht niet gevonden
rcexplain.2: parancs nem található
rcexplain.2: perintah tidak ditemukan
rcexplain.2: príkaz nenájdený
rcexplain.2: příkaz nenalezen
rcexplain.2: команда не найдена
rcexplain.2: командата не е открита
rcexplain.2: 命令找不到
rcexplain.2: コマンドが見つかりません