CHIP uses flash memory as a solid-state disc replacement. It is based on NAND technology.
All flash memory has a limited lifetime. Flash is best used in a "read frequently, write rarely" model because repeated writing tends to "wear out" the memory. (Also, writing speed is much slower than reading speed.)
Here are some steps to extend the life of CHIP's flash by minimizing writes to it.
Create ramdisk for application logging
Thanks to MEitelwein's project for this idea.
Many applications you might run on CHIP generate logs of their activity. For example, web servers log every access to the server. If you have a particularly "chatty" application, you can arrange to have its logs written to a "ram disk", which is kept in system RAM instead of writing it to flash. Be aware however that if CHIP reboots, the contents of your ramdisk file system is lost forever. (Although you could write a shutdown script which backs up the contents to flash prior to shutdown.)
Here's how to create a "ram disk" file system:
sudo mkdir /ramdisk sudo vim /etc/fstab # or use your own favorite editor, maybe pico.
In the editor, add the following line to the end of the file:
tmpfs /ramdisk tmpfs defaults 0 1
Write the file, exit the editor, and enable the file system by entering:
sudo mount -a
Check to make sure it worked:
Included in the list should be the line:
tmpfs 253552 0 253552 0% /ramdisk
(Some of your numbers might be different.)
Since the file system is empty, both now and at boot time, you probably want to write a script to populate it with properly-owned directories. For example, to redirect apache's logs:
#!/bin/sh mkdir /ramdisk/apache_log chown root:adm /ramdisk/apache_log rm -rf /var/log/apache2 ln -s /ramdisk/apache_log /var/log/apache2
This script can be included in the systemd framework as a one-shot unit, and apache can be set to depend upon it.
Finally, remember that files on ramdisk are limited in size. If they grow too large, Unix will start to use swapspace, with both slows the system way down and also defeats the purpose since it writes to flash. So keep the files small by periodically cleaning them up. (e.g. with apache, see this post.)
Minimize syslog chattiness
rsyslogd-2007: action 'action 17' suspended
Due to a bug in Linux syslog, CHIP's /var/log/messages file will sometime start filling up with once-per-minute messages of the form (timestamps omitted):
chip rsyslogd-2007: action 'action 17' suspended, next retry is ... [try http://www.rsyslog.com/e/2007 ]
I followed these instructions:
sudo vi /etc/rsyslog.conf # or any other editor, like nano.
Near the bottom should be the lines:
daemon.*;mail.*;\ news.err;\ *.=debug;*.=info;\ *.=notice;*.=warn |/dev/xconsole
Comment these lines out by putting a "#" in front of each line:
#daemon.*;mail.*;\ # news.err;\ # *.=debug;*.=info;\ # *.=notice;*.=warn |/dev/xconsole
Write the file, exit the editor, and enter:
sudo service rsyslog restart
I haven't seen the message since.
By default, Linux writes a number of log messages to /var/log/daemon.log every time you log into CHIP and log back out. Here's an example of one of the messages:
chip systemd: Starting user-1000.slice.
(timestamp omitted) There are other messages associated with it.
According to this, you can disable these message by entering:
sudo loginctl enable-linger chip
It doesn't eliminate all message logging, but it greatly reduces it. And by the way, the command appears to be "sticky". I.e. it is remembered after a reboot. So there is no need to re-execute the command with each reboot.
Read-Only Root Filesystem
Steps below (tested on headless 4.4 chip with Debian Jessie) will reconfigure root filesystem to be read-only @ boot. Inspired by Raspberry pi tutorials: https://hallard.me/raspberry-pi-read-only/ http://petr.io/en/blog/2015/11/09/read-only-raspberry-pi-with-jessie/
apt-get remove cron logrotate -y --force-yes apt-get install busybox-syslogd -y --force-yes
mount /tmp as tmpfs
systemctl enable tmp.mount
rm -r /var/run /var/spool /var/lock /var/log /var/tmp echo "D /tmp/var/run 1777 root root -" > /etc/tmpfiles.d/rovar.conf echo "D /tmp/var/spool 1777 root root -" >> /etc/tmpfiles.d/rovar.conf echo "D /tmp/var/lock 1777 root root -" >> /etc/tmpfiles.d/rovar.conf echo "D /tmp/var/log 1777 root root -" >> /etc/tmpfiles.d/rovar.conf echo "D /tmp/var/tmp 1777 root root -" >> /etc/tmpfiles.d/rovar.conf echo "D /tmp/var/lib/dhcp 1777 root root -" >> /etc/tmpfiles.d/rovar.conf echo "D /tmp/var/lib/NetworkManager 1777 root root -" >> /etc/tmpfiles.d/rovar.conf echo "D /tmp/var/lib/systemd/rfkill 1777 root root -" >> /etc/tmpfiles.d/rovar.conf ln -s /tmp/var/run /var/run ln -s /tmp/var/spool /var/spool ln -s /tmp/var/lock /var/lock ln -s /tmp/var/log /var/log ln -s /tmp/var/tmp /var/tmp rm -r /var/lib/dhcp ln -s /tmp/var/lib/dhcp /var/lib/dhcp rm -r /var/lib/NetworkManager ln -s /tmp/var/lib/NetworkManager /var/lib/NetworkManager rm -r /var/lib/systemd/rfkill ln -s /tmp/var/lib/systemd/rfkill /var/lib/systemd/rfkill
Deal with special files
rm /var/lib/systemd/random-seed ln -s /tmp/random-seed /var/lib/systemd/random-seed touch /tmp/dhcpcd.resolv.conf rm /etc/resolv.conf ln -s /tmp/dhcpcd.resolv.conf /etc/resolv.conf echo "f /tmp/random-seed - - - - -" > /etc/tmpfiles.d/ro.conf echo "f /tmp/dhcpcd.resolv.conf - - - - -" >> /etc/tmpfiles.d/ro.conf
fix random-seed dependency
sed -i '/^After=/ s/$/ systemd-tmpfiles-setup.service/' /lib/systemd/system/systemd-random-seed.service
NTP daemon driftfile location
sed -i 's/\(driftfile \)\(.*\)/\1\/tmp\/ntp.drift/' /etc/ntp.conf
UBI watchdog -> write stats to writable location
sed -i 's/var\/cache/tmp/g' /etc/systemd/system/ubihealthd.service
Finally, switch to Read-Only filesystem
echo "/dev/mtdblock3 0 0x400000 0x4000" | sudo tee -a /etc/fw_env.config fw_setenv bootargs root=ubi0:rootfs rootfstype=ubifs ro fastboot noswap earlyprintk ubi.mtd=4
Reboot and enjoy!