Install ccache on your host, and setup cache folder to 1GiB maximum size:

sudo apt-get install ccache
sudo mkdir /var/cache/ccache
sudo CCACHE_DIR=/var/cache/ccache ccache -M 1G

Prepare hook to install ccache and fixup permissions:

# cat /tmp/ccache/D01ccache
#!/bin/bash

apt-get install ccache

chown -R pbuilder /var/cache/ccache

Prepare config file

# cat /tmp/ccache/env
export CCACHE_DIR=/var/cache/ccache
export PATH=/usr/lib/ccache:$PATH

Build a source package

sudo cowbuilder --build dtach_0.8-2.1.dsc --basepath
/tmp/jessie.amd64.cow --hookdir /tmp/ccache --buildplace /tmp
--bindmounts /var/cache/ccache --configfile /tmp/ccache/env

The --bindmounts option will provide the host’s ccache to cowbuilder, --hookdir installs ccache inside and --configfile actually enables ccache.

Use CCACHE_DIR=/var/cache/ccache ccache -s to checkout cache usage, e.g.

cache directory                     /var/cache/ccache
primary config                      /var/cache/ccache/ccache.conf
secondary config      (readonly)    /etc/ccache.conf
cache hit (direct)                  3492
cache hit (preprocessed)             227
cache miss                          2483
cache hit rate                     59.96 %
called for link                      466
called for preprocessing             114
compile failed                        23
preprocessor error                    36
bad compiler arguments                 6
autoconf compile/link                 85
no input file                         73
cleanups performed                     0
files in cache                      4835
cache size                         567.8 MB
max cache size                       1.0 GB

The only way I got duplex printing to work from the command line:

lp -o sides=two-sided-long-edge foo.pdf

Firefox’s Web Content using 50% CPU? Close that Google Search Result tab.

Getting the discard operation is not supported when running fstrim on a kvm guest? Make sure to

• use virtio-scsi
• pass discard='unmap' to the disk driver
• use a machine type >= 2.1, e.g. pc-i440fx-2.3

Following http://without-systemd.org/wiki/index.php/Debian_Stretch and adding a pin on *systemd* will lead to libvirt-daemon-system being uninstalled though (dependency chain: libvirt-daemon-system -> polkit -> libpam-systemd).

It is possible to build rebuild polkit without systemd, see https://github.com/bidaian/no-systemd, but that means tracking another package diversion.

An alternative solution is to just not use systemd as init, put keep the other packages installed:

apt-get install sysvinit-core sysvinit-utils
apt-get remove --purge systemd-sysv

A recent Windows 7 installation started crashing with a Bluescreen of Death after installing the qlx driver inside the guest. Switching back to the vga model allowed me to boot it again:

<video>
  <model type='vga' vram='16384' heads='1' primary='yes'/>
  <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
</video>

If you get that message over and over again, unset the http proxy in Firefox.

Also, it only worked for me with Firefox 53 ESR 32 Bit (due to NAPI stuff) and Flash Player 27 Beta (due to a bug in 27 Release).

According to https://cygwin.com/ml/cygwin/2015-03/msg00379.html,

[…] it was apparently caused by a too-rapid startup at boot of cygserver, which apparently could not connect to LDAP at that early stage.

To remotly start terminator on a minimal CentOS install these packages:

yum install terminator xauth dbus-x11.x86_64 dejavu-sans-fonts.noarch dejavu-sans-mono-fonts.noarch

Without the font packages you’ll only see boxes.

If ssh -X fails with X11 forwarding request failed on channel 0 when connecting to an IPv4 only host, check your /etc/ssh/sshd_config for AddressFamily inet:

Specifies which address family should be used by sshd(8). Valid arguments are “any”, “inet” (use IPv4 only), or “inet6” (use IPv6 only). The default is “any”.