Reduce SD Card wearing

Transient log
Finding SD card erase size

Start logging disc access and kernel log:

sysctl vm.block_dump=1
dmesg -e -T -w 

Stop logging:

sysctl vm.block_dump=0

/etc/rc.local

...
echo noop > /sys/block/mmcblk0/queue/scheduler
exit 0

/etc/fstab

tmpfs   /tmp                     tmpfs   defaults,nosuid,nodev,mode=1777,size=10%        0       0
tmpfs   /var/tmp                 tmpfs   defaults,nosuid,nodev,mode=1777,size=10%        0       0
tmpfs   /var/cache/apt/archives  tmpfs   defaults,nosuid,nodev,mode=1777,size=80%        0       0

Move some volatile dirs to tmp folder:

rm -rf /var/run /var/lock
ln -s /run /var/run
ln -s /run/lock /var/lock

rm -rf /var/lib/dhcp/ /var/spool
ln -s /tmp /var/lib/dhcp
ln -s /tmp /var/spool;

systemctl stop mosquitto
systemctl disable mosquitto

apt-get remove anacron

Remove syslog

dpkg --purge rsyslog

Use syslog from busybox package with circular log buffer in RAM:

apt-get install busybox-syslogd

SYSLOG_OPTS="-C256 -L -R remote.host.org"
KLOG_OPTS=""

Use journald and configure it to use RAM:

/etc/systemd/journald.conf

Storage=volatile
Compress=yes

Check TRIM support

sudo hdparm -I /dev/sda | grep "TRIM supported"

/etc/systemd/system/fstrim.service

[Unit]
Description=Discard unused blocks

[Service]
Type=oneshot
ExecStart=/sbin/fstrim -av

/etc/systemd/system/fstrim.timer

[Unit]
Description=Discard unused blocks once a week
Documentation=man:fstrim

[Timer]
OnCalendar=weekly
AccuracySec=1h
Persistent=true

[Install]
WantedBy=multi-user.target

systemctl daemon-reload
systemctl enable fstrim.timer

Bad magic number in super-block

[ 7000.203888] F2FS-fs (sda2): Magic Mismatch, valid(0xf2f52010) - read(0x0)
[ 7000.203926] F2FS-fs (sda2): Can't find valid F2FS filesystem in 1th superblock

e2fsck /dev/sda2
e2fsck 1.42.12 (29-Aug-2014)
ext2fs_open2: Bad magic number in super-block
e2fsck: Superblock invalid, trying backup blocks...
/dev/sda2: recovering journal
e2fsck: unable to set superblock flags on /dev/sda2


/dev/sda2: ***** FILE SYSTEM WAS MODIFIED *****

/dev/sda2: ********** WARNING: Filesystem still has errors **********

To get superblock backups, simulate fs creation

sudo mke2fs -n /dev/xxx

Then run fsck with superblock backup

sudo e2fsck -b block_number /dev/xxx