Debian

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Install TCP BBR Kernel Patches

TCP BBR is a new congestion controlling algorithm that is designed to respond to actual congestion instead of packet loss. This results in a dramatic increase in transfer speeds. This applies to any Linux distribution running Kernel 4.9+ with BBR patches.

# Check TCP BBR supported.
uname -r

# Both parameters should be returned.
egrep 'CONFIG_TCP_CONG_BBR|CONFIG_NET_SCH_FQ' /boot/config-$(uname -r)

Enable BBR Support

/etc/sysctl.d/10_custom_kernel_bbr.conf

0644 root:root

net.core.default_qdisc=fq
net.ipv4.tcp_congestion_control=bbr

sysctl -p  # Or reboot.

Disable IPv6

Disable if IPv6 is not being actively used to prevent any IPv6 misconfiguration attacks.

/etc/sysctl.d/10_disable_ipv6.conf

0644 root:root

net.ipv6.conf.all.disable_ipv6=1
net.ipv6.conf.default.disable_ipv6=1
net.ipv6.conf.lo.disable_ipv6=1

sysctl -p  # Or reboot.

Operations

Make RAW Disk Image of Physical Disk

DD can be used to make a RAW image of a disk, and can be mounted in other linux systems for use.

# Copy disk block device to a file.
dd if=/dev/{BLOCK} of=/some/filesystem/{IMAGE}.raw bs=1M conv=noerror,sync status=progress

# Mount RAW disk image for use.
losetup -f -P /some/filesystem/{IMAGE}.raw
losetup -l
mount /dev/loop0p1 /mnt/test/
umount /dev/loop0p1
losetup -d /dev/loop0

Apt Auto Selection

Automatically select user-required options during package install.

This is used for configuration management and preseeding for automatic installs that require user input.

Get debconf Options

Determine debconf options used by installing the package with the options set.

apt install debconf-utils
apt install {PACKAGE}
debconf-get-selections | grep {PACKAGE}

Set debconf Options

On target machines, set options before installing the package. This will remove the prompts from apt.

Tip

debconf will list with tabs for easy reading. When setting selections separate with a space, otherwise the extra whitespace will be included with the option.

echo "{PACKAGE}-{VERSION} package/option {NAME} {VALUE}" | debconf-set-selections
apt install {PACKAGE}

Example

apt install mysql-server debconf-utils
debconf-get-selections | grep mysql-server
> mysql-server-5.5        mysql-server/root_password_again        password
> mysql-server-5.5        mysql-server/root_password      password
> mysql-server-5.5        mysql-server/error_setting_password     error
> mysql-server-5.5        mysql-server-5.5/postrm_remove_databases        boolean false
> mysql-server-5.5        mysql-server-5.5/start_on_boot  boolean true
> mysql-server-5.5        mysql-server-5.5/nis_warning    note
> mysql-server-5.5        mysql-server-5.5/really_downgrade       boolean false
> mysql-server-5.5        mysql-server/password_mismatch  error
> mysql-server-5.5        mysql-server/no_upgrade_when_using_ndb  error

echo "mysql-server-5.5        mysql-server-5.5/start_on_boot  boolean true"  | debconf-set-selections
apt install mysql-server-5.5