Clear Linux bash history

While having history available with the simple use of the up arrow is a convenience feature common to most linux builds it can come with some risk. One such risk is when you have inadvertently typed a password instead of a command, or had to pipe credentials into a command.

Thankfully, you can clear the entire history with a variety of methods, the most common are below but others are available in the references.


history -c && history -w


cat /dev/null > ~/.bash_history && history -c && exit

REFERENCES:

Cannot load VirtualBox after upgrading Ubuntu

If your computer uses SecureBoot, you may occasionally encounter this problem after upgrading the operating system. Thankfully, the solution is simple after some initial setup the first time.

The error generally reads something like: Could not load ‘modprobe vboxdrv’

First time:

  1. Create signing keys:

    openssl req -new -x509 -newkey rsa:2048 -keyout MOK.priv -outform DER -out MOK.der -nodes -days 36500 -subj "/CN=Descriptive name/"

  2. Sign the module (vboxdrv for this example):

    sudo /usr/src/linux-headers-$(uname -r)/scripts/sign-file sha256 ./MOK.priv ./MOK.der $(modinfo -n vboxdrv)

  3. Register the keys to Secure Boot:

    sudo mokutil --import MOK.der

  4. Supply a password for later use after reboot
  5. Reboot and follow instructions to Enroll MOK (Machine Owner Key).
  6. Restart after enrolling
  7. After the reboot, you may also need to load the module:
    sudo modprobe vboxdrv

After future updates you might re-encounter the problem, then you just need:

  1. sudo /usr/src/linux-headers-$(uname -r)/scripts/sign-file sha256 ./MOK.priv ./MOK.der $(modinfo -n vboxdrv)
  2. sudo modprobe vboxdrv

REFERENCES:

Modify Ubuntu Swappiness for performance

Sometimes, it is possible to improve the performance of Ubuntu on older hardware by modifying the disk swapping behavior.

Check your current setting:

cat /proc/sys/vm/swappiness

To modify the behavior, just change the value and reboot. Most documentation recommends trying a value of 10.

sudo vi /etc/sysctl.conf

Add (or change):

# Decrease swappiness value (default:60)
vm.swappiness=10

REFERENCES:

Google Chrome installation for Ubuntu

With a few simple steps, Google Chrome can be installed on Ubuntu.


wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | sudo apt-key add -


sudo sh -c 'echo "deb http://dl.google.com/linux/chrome/deb/ stable main" >> /etc/apt/sources.list.d/google.list'


sudo apt-get update


sudo apt-get install google-chrome-stable

or…


sudo apt-get install google-chrome-beta

Clear Ubuntu ‘bash’ history

After a lot of use, your history file can become full of a lot of old commands… once in a while, it can be useful (and safer) to clean them up.

NOTE: this can be especially important if you have ever used a password as a command line parameter as it is stored without encryption in a text file.

Preferred:

cat /dev/null > ~/.bash_history && history -c && exit

Also useful:

history -c
history -w

REFERENCES:

Install Fail2Ban on Ubuntu to protect services

Many common adminstrative services such as VPN and SSH are exposed on known port numbers, unfortunately this makes it easy for hackers to use tools to attempt to access the systems. Use of countermeasures such as Fail2Ban can block them after a few failed attempts.

Installation Steps:

  1. sudo apt-get install fail2ban
  2. sudo cp /etc/fail2ban/jail.conf /etc/fail2ban/jail.local
  3. sudo vi /etc/fail2ban/jail.local
  4. Update:
    destemail & sender
  5. OPTIONAL:
    Splunk:
    sudo /opt/splunkforwarder/bin/splunk add monitor /var/log/fail2ban.log -index main -sourcetype Fail2Ban

    Splunk (manual):
    sudo vi /opt/splunkforwarder/etc/apps/search/local/inputs.conf

    [monitor:///var/log/fail2ban.log]
    disabled = false
    index = main
    sourcetype = Fail2Ban

  6. sudo service fail2ban restart

REFERENCES:

Adding OpenSSH server logs to Splunk

By default, in most Linux distros, OpenVPN log output goes to the authlog, which is usually at /var/log/auth.log, as such it is trivial to add them to Splunk monitoring:

Splunk:
sudo /opt/splunkforwarder/bin/splunk add monitor /var/log/auth.log -index main -sourcetype OpenSSH

Splunk (manual):
sudo vi /opt/splunkforwarder/etc/apps/search/local/inputs.conf


[monitor:///var/log/auth.log]
disabled = false
index = main
sourcetype = OpenSSH

REFERENCES:

Adding OpenVPN logs to Splunk on Ubuntu

By default, in most Linux distros, OpenVPN log output goes to the syslog, which is usually at /var/log/syslog. However, your config files can set the logfile location explicitly, as shown below:

  1. sudo vi /etc/openvpn/server.conf
  2. Change or add:
    log-append /var/log/openvpn.log
  3. Restart to use the new config:
    sudo service openvpn restart
  4. Add to Splunk forwarder:
    sudo /opt/splunkforwarder/bin/splunk add monitor /var/log/openvpn.log -index main -sourcetype OpenVPN

    Splunk (manual):
    sudo vi /opt/splunkforwarder/etc/apps/search/local/inputs.conf

    [monitor:///var/log/openvpn.log]
    disabled = false
    index = main
    sourcetype = OpenVPN

REFERENCES:

Install WireShark on Ubuntu Linux

WireShark is an invaluable tool in recording and reviewing network traffic, it was previously known as Ethereal and is available for a variety of platforms.

Installation can sometimes be hard to remember as use by non-superusers requires additional configuration in Linux.

  1. Add the repository and install:

    sudo add-apt-repository ppa:wireshark-dev/stable

    sudo apt-get update

    sudo apt-get install wireshark

  2. During installation, the following will appear, chose "Yes" for most instances.


    Should non-super users be able to capture packets - Yes / No?

  3. If you need to change the value you selected, you can always re-run the following:


    dpkg-reconfigure wireshark-common

  4. Add the user to the wireshark group so that they can capture traffic:


    add user to group:
    sudo usermod -a -G wireshark username
    id username

  5. If you need additional information, you can always RTFM:


    sudo vi /usr/share/doc/wireshark-common/README.Debian.

REFERENCES:

Disable IPv6 on Ubuntu

Ubuntu updates occasionally fail due to IPv6 update servers not being reachable. While I prefer to keep IPV6 activated, this approach will allow you to disable it for updates, simply reverse the steps to re-enable afterwards!

  1. Update the configuration file…

    sudo vi /etc/sysctl.conf

    ADD:

    # IPv6 disabled
    net.ipv6.conf.all.disable_ipv6 = 1
    net.ipv6.conf.default.disable_ipv6 = 1
    net.ipv6.conf.lo.disable_ipv6 = 1

  2. Then, you must enable the change…

    sudo sysctl -p

  3. To verify…


    ifconfig