Problem with apt-get update in crontab @reboot

Question

I wrote a simple bash script to keep my system updated, and put it on a crontab to execute @reboot:

(sudo  apt-get update) >> /home/raphael/Documents/Logs/updateLogs.txt
(sudo  apt-get upgrade -y) >> /home/raphael/Documents/Logs/updateLogs.txt
(sudo apt autoremove -y) >> /home/raphael/Documents/Logs/updateLogs.txt
(sudo date ) >> /home/raphael/Documents/Logs/updateLogs.txt

However, every time I check the updateLogs.txt file I encounter these errors:

Err:1 http://packages.microsoft.com/repos/vscode stable InRelease
  Temporary failure resolving 'packages.microsoft.com'
Err:2 http://br.archive.ubuntu.com/ubuntu xenial InRelease
  Temporary failure resolving 'br.archive.ubuntu.com'
Err:3 http://br.archive.ubuntu.com/ubuntu xenial-updates InRelease
  Temporary failure resolving 'br.archive.ubuntu.com'
Err:4 http://br.archive.ubuntu.com/ubuntu xenial-backports InRelease
  Temporary failure resolving 'br.archive.ubuntu.com'
Err:5 http://security.ubuntu.com/ubuntu xenial-security InRelease
  Temporary failure resolving 'security.ubuntu.com'
Err:6 http://packages.elementary.io/appcenter xenial InRelease
  Temporary failure resolving 'packages.elementary.io'
Err:7 http://ppa.launchpad.net/danielrichter2007/grub-customizer/ubuntu xenial InRelease
  Temporary failure resolving 'ppa.launchpad.net'
Err:8 http://ppa.launchpad.net/elementary-os/stable/ubuntu xenial InRelease
  Temporary failure resolving 'ppa.launchpad.net'
Err:9 http://ppa.launchpad.net/papirus/papirus/ubuntu xenial InRelease
  Temporary failure resolving 'ppa.launchpad.net'
Err:10 http://ppa.launchpad.net/elementary-os/os-patches/ubuntu xenial InRelease
  Temporary failure resolving 'ppa.launchpad.net'
Err:11 http://dl.google.com/linux/chrome/deb stable InRelease
  Temporary failure resolving 'dl.google.com'
Err:12 http://repository.spotify.com stable InRelease
  Temporary failure resolving 'repository.spotify.com'

If I run manually the script I get the expected results:

Hit:1 http://br.archive.ubuntu.com/ubuntu xenial InRelease
Hit:2 http://br.archive.ubuntu.com/ubuntu xenial-updates InRelease
Get:3 http://br.archive.ubuntu.com/ubuntu xenial-backports InRelease [102 kB]
Ign:4 http://dl.google.com/linux/chrome/deb stable InRelease
Hit:5 http://repository.spotify.com stable InRelease
Hit:6 http://ppa.launchpad.net/danielrichter2007/grub-customizer/ubuntu xenial InRelease
Hit:7 http://dl.google.com/linux/chrome/deb stable Release
Hit:8 http://packages.microsoft.com/repos/vscode stable InRelease
Hit:10 http://ppa.launchpad.net/elementary-os/stable/ubuntu xenial InRelease
Hit:11 http://ppa.launchpad.net/papirus/papirus/ubuntu xenial InRelease
Hit:12 http://ppa.launchpad.net/elementary-os/os-patches/ubuntu xenial InRelease
Hit:13 http://packages.elementary.io/appcenter xenial InRelease
Get:14 http://security.ubuntu.com/ubuntu xenial-security InRelease [102 kB]
Fetched 204 kB in 5s (38,6 kB/s)

At first I thought it was a wi-fi problem, so I put an Ethernet cable in my notebook, but I got the same results. Any thoughts on why this happens?

Answer 1

Try to "wait" a bit before running apt update. You can empirically find optimal time to sleep, or you can use this code from this post:

#!/bin/bash

function check_online
{
    netcat -z -w 5 8.8.8.8 53 && echo 1 || echo 0
}

# Initial check to see if we're online
IS_ONLINE=check_online
# How many times we should check if we're online - prevents infinite looping
MAX_CHECKS=5
# Initial starting value for checks
CHECKS=0

# Loop while we're not online.
while [ $IS_ONLINE -eq 0 ];do
    # We're offline. Sleep for a bit, then check again

    sleep 10;
    IS_ONLINE=check_online

    CHECKS=$[ $CHECKS + 1 ]
    if [ $CHECKS -gt $MAX_CHECKS ]; then
        break
    fi
done

if [ $IS_ONLINE -eq 0 ]; then
    # We never were able to get online. Kill script.
    exit 1
fi

# Now we enter our normal code here. The above was just for online checking