Log2Zram

Usefull for IoT / maker projects for reducing SD, Nand and Emmc block wear via log operations. Uses Zram to minimise precious memory footprint and extremely infrequent write outs.

Log2Zam is a lower write fork https://github.com/azlux/log2ram based on transient log for Systemd here : A transient /var/log

Can not be used for mission critical logging applications where a system crash and log loss is unaceptable. If the extremely unlikely event of a system crash is not a major concern then L2Z can massively reduce log block wear whilst maintinaing and extremely tiny memory footprint.

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Menu

1. Install
2. Config
3. It is working ?
4. Uninstall

Install

sudo apt-get install git rsync
git clone https://github.com/StuartIanNaylor/log2zram
cd log2zram
sudo sh install.sh

Customize

variables :

In the file /etc/log2zram.conf sudo nano /etc/log2zram.conf to edit:

# Size for the zram memory used, it defines the mem_limit for the zram device.
# The default is 20M and is basically enough for minimal applications.
# Because aplications can often vary in logging frequency this may have to be tweaked to suit application .
SIZE=20M
# COMP_ALG this is any compression algorithm listed in /proc/crypto
# lz4 is fastest with lightest load but deflate (zlib) and Zstandard (zstd) give far better compression ratios
# lzo is very close to lz4 and may with some binaries have better optimisation
# COMP_ALG=lz4 for speed or deflate for compression, lzo or zlib if optimisation or availabilty is a problem
COMP_ALG=lz4
# LOG_DISK_SIZE is the uncompressed disk size. Note zram uses about 0.1% of the size of the disk when not in use
# LOG_DISK_SIZE is expected compression ratio of alg chosen multiplied by log SIZE where 300% is an approx good level.
# lzo/lz4=2.1:1 compression ratio zlib=2.7:1 zstandard=2.9:1
# Really a guestimate of a bit bigger than compression ratio whilst minimising 0.1% mem usage of disk size
LOG_DISK_SIZE=60M
# PRUNE_LEVEL if log size is below this level then old logs will be moved to hdd.log enter as %
# Moving the old logs will restart log rotation as old logs will no longer exist in /var/log/oldlog
# In normal operation hitting 50% or above can take many hourly cycles so a higher prune level is a balance
# 55-60% is probably a good level as too high will restart logrotation and create less history  
PRUNE_LEVEL=60

refresh time:

By default Log2Zram checks available log space every hour. It them makes a comparison of the percentage set via Prune_Level and only writes out old logs to disk when triggered and then removes the collected old logs from zram space.

It is working?

You can now check the mount folder in ram with (You will see lines with log2ram if working)

# df -h
…
log2ram          40M  532K   40M   2% /var/log
…

# mount
…
log2ram on /var/log type tmpfs (rw,nosuid,nodev,noexec,relatime,size=40960k,mode=755)
…

Testing

sudo service log2ram reload

Checks PRUNE_LEVEL < available free space if true will move and clean /var/log/oldlog to hdd.log

sudo logrotate -vf /etc/logrotate.conf

Force the daily logrotate with verbose output

The log for log2ram will be written at: /var/log/log2ram.log

Compressor name	Ratio	Compression	Decompress.
zstd 1.3.4 -1	2.877	470 MB/s	1380 MB/s
zlib 1.2.11 -1	2.743	110 MB/s	400 MB/s
brotli 1.0.2 -0	2.701	410 MB/s	430 MB/s
quicklz 1.5.0 -1	2.238	550 MB/s	710 MB/s
lzo1x 2.09 -1	2.108	650 MB/s	830 MB/s
lz4 1.8.1	2.101	750 MB/s	3700 MB/s
snappy 1.1.4	2.091	530 MB/s	1800 MB/s
lzf 3.6 -1	2.077	400 MB/s	860 MB/s

Uninstall

chmod +x /usr/local/bin/uninstall-log2ram.sh && sudo /usr/local/bin/uninstall-log2ram.sh

Also /var/oldlog contains the pruned logs from install delete if not required (prob not)