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Table of Contents
Website Self Hosting
IP
Dynamic DNS service if you don't have a static IP.
Hardware
Any old machine, or even better an old laptop (less power, less noise, less room).
Flash cache
Introduction
Solutions for hybriding flash drives and hard drives have been experimented to save power on laptops, but it is quite complex in the general case and there is no final-user implementation yet, and the gains are limited on an everyday use machine. However it is a lot more efficient and simple on a server, as there are a lot less interactions with users and the panel of activities is largely reduced. Hence you only have to put on flash disk a few directories and files that the system regularly write to (the cache in RAM is enough for reading), and the disk can remain spun down for hours or days if you don't start unusual applications.
You need an USB stick or SD Card of at least 2GB (4GB is advised), and an init script to mount and fetch during early boot process, and unmount and flush during late shutdown process. For instance I wrote this one for Gentoo: /etc/init.d/fcache with conf /etc/conf.d/fcache, add it to the boot runlevel (rc-update add fcache boot
).
As an example, my server (a Core2 Duo laptop) consumes 12-13W (saved 1W stopping the hard drive), makes no noise at all (no fan, no hard drive), and the hard drive remains stopped for several days, as long as I don't do something unusual (I can even log in with ssh, with export display, as root, use firefox, without waking up the drive).
What to cache
The main directories you need to take care of are:
/var
/tmp
if not already mounted as tmpfs in ram/home
if you have enough space
If you cannot cache your whole home folder, you can cache a few important files by putting them in a ~/.fcache
directory. Then either create a symbolic link or configure the program to use this new location:
~/.history
: shell history for all users including root; set the new location with the $HISTFILE environment variable for zsh in .zshrc file.~/.lesshst
:less
history; works with symlink.~/.xsession-errors
: gdm file; needs version >2.32.1 so that symlink works, with previous versions you have to recompile it after hard changing “.xsession-errors” to “.fcache/.xsession-errors” (in filedaemon/slave.c
for version 2.20).~/.Xauthority
: xauth file;- for GDM: set
[daemon] UserAuthDir=/home/cyril/.fcache
in/etc/X11/gdm/custom.conf
- for SSHD: set
XAUTHORITY=/home/cyril/.fcache/.Xauthority
in~/.ssh/environment
, andPermitUserEnvironment yes
in/etc/ssh/sshd_config
- for SU: set
cyril
(your username) in/root/.xauth/import
, to avoid creation of/root/.xauthXXXXX
files - for the rest: set
export XAUTHORITY=/home/cyril/.fcache/.Xauthority
in~/.zshenv
file (or if there is somewhere else upstream enough to avoid point for SSHD it would be better)
Configure smartd
If you run smartd
daemon, it will wakes up the drive every 30min by default to perform some checks. You have to tell it to not do tests if the drive is in standby powermode. Edit /etc/smartd.conf
:
-DEVICESCAN +#DEVICESCAN +/dev/sda -d ata -n standby
Finding the guilty files
You can use a script similar to this one to monitor what files are being used and add them to the cache (you can then grep “sda” and “dirtied”), and monitor if the drive remains spun down:
#!/bin/sh rm -f /mnt/ram/disk.log dmesg -c #sudo sysctl vm.block_dump=1 echo 1 > /proc/sys/vm/block_dump watch --interval=5 'dmesg -c | grep sda >> /mnt/ram/disk.log ; hdparm -C /dev/sda | grep "drive state" | cut -d":" -f2 >> /mnt/ram/disk.log' echo 0 > /proc/sys/vm/block_dump
You can also use strace -p <PID> -e trace=write -s 128
if you don't have enough information about some files name and location.
Configure the drive to go to standby
Configure hdparm to put the drive to standby after some time of inactivity. For instance to test with 10 minutes:
hdparm -S 120 /dev/sda
And for final configuration copy /usr/lib/pm-utils/power.d/harddrive
file to /etc/pm/power.d/
and set variable DRIVE_SPINDOWN_VALUE_BAT
to 241 for instance for 30 minutes (check option -S in hdparm's man page).
Optional extra configuration
You can try to tune how syslog will write to the disk to save the flash life, in /etc/syslog-ng/syslog-ng.conf
:
options { mark_freq(0); # remove --MARK-- lines issued by default every 20s flush_lines(20); flush_timeout(60000); # in ms };