fastq-dump.2.3.5: 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/fastq-dump.2.3.5 - from package: sra-toolkit

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

Error in other languages:
fastq-dump.2.3.5: bevel nie gevind nie
fastq-dump.2.3.5: comandă negăsită
fastq-dump.2.3.5: comando não encontrado
fastq-dump.2.3.5: commande introuvable
fastq-dump.2.3.5: command not found
fastq-dump.2.3.5: käsku ei ole
fastq-dump.2.3.5: không tìm thấy lệnh
fastq-dump.2.3.5: komanda nerasta
fastq-dump.2.3.5: Kommando nicht gefunden.
fastq-dump.2.3.5: kommandot finns inte
fastq-dump.2.3.5: komut yok
fastq-dump.2.3.5: nie znaleziono polecenia
fastq-dump.2.3.5: níor aimsíodh an t-ordú
fastq-dump.2.3.5: no se encontró la orden
fastq-dump.2.3.5: no s'ha trobat l'ordre
fastq-dump.2.3.5: opdracht niet gevonden
fastq-dump.2.3.5: parancs nem található
fastq-dump.2.3.5: perintah tidak ditemukan
fastq-dump.2.3.5: príkaz nenájdený
fastq-dump.2.3.5: příkaz nenalezen
fastq-dump.2.3.5: команда не найдена
fastq-dump.2.3.5: командата не е открита
fastq-dump.2.3.5: 命令找不到
fastq-dump.2.3.5: コマンドが見つかりません