¶ rescan scsi disk
This you need after vm disk expansion in runtime
rebooting is recommended at end of work for testing
for d in /sys/block/sd*/device/rescan ; do echo "scanning $d" ; echo 1 > $d ; done
¶ expand last partition in disk
lsblk
DISK=sdb
PART=1
parted /dev/$DISK resizepart $PART 100%
lsblk
¶ backup and restore mbr of a disk
- Backing up MBR stored on /dev/sdX
dd if=/dev/sdX of=/tmp/sda-mbr.bin bs=512 count=1
- Restore partition table to disk
dd if= sda-mbr.bin of=/dev/sdX bs=1 count=64 skip=446 seek=446
Restore partition table and boot loader
dd if= sda-mbr.bin of=/dev/sdX bs=512 count=1
¶ backup helper script
echo '#!/bin/sh
cp -av "$1" "$1.$(date +%Y%m%d%H%M%S)"
' > /usr/local/bin/backup
chmod 755 /usr/local/bin/backup
¶ create sparse image files with dd
dd if=/dev/zero of=guest.raw bs=1 count=0 seek=8G
¶ create random data fast
50Gig of data with 5 threads
for i in {1..5} ; do ( openssl enc -aes-256-ctr -pass pass:"$(dd if=/dev/urandom bs=128 count=1 2>/dev/null | base64)" -nosalt < /dev/zero 2>&1 | dd of=/tmp/file_10G.$i bs=1M count=10k iflag=fullblock ) & done
¶ create 5 data generating threads which create infinite data files
for i in {1..5} ; do ( openssl enc -aes-256-ctr -pass pass:"$(dd if=/dev/urandom bs=128 count=1 2>/dev/null | base64)" -nosalt < /dev/zero 2>&1 | dd of=/tmp/file.$i) & done
# stop data generation, started with command above
pkill -9 -f dd
¶ ultra fast file copy of large file volumes
tar --ignore-failed-read -C $SRC_DATA/ -cf - . | mbuffer -L -s 256k -m 1G -P 85 | tar --ignore-failed-read -C $DST_DATA/ -xf -
¶ read HD smart status
smartctl -a /dev/sda
smartctl -H /dev/sda
¶ read udev disk attributes
read disk serial
udevadm info --query=all --name=/dev/sda | grep ID_SERIAL_SHORT | cut -d= -f2
¶ save and restore acl attributes
be careful, restore deleted my suid permissions 
getfacl -R . >acl.txt
setfacl --restore acl.txt
getfacl -R $(ls -d /* | egrep -v 'dev|proc|selinux|sys|lost+') > /etc/acl.txt
¶ turn off auto hard disc boot scanning for extN and reduce root preserved space
tune2fs -c 0 -i 0 -m 0 /dev/VG0/data
¶ format Fat32 usb stick
DEV=/dev/sdX
umount ${DEV}* $DEV
dd if=/dev/zero of=$DEV bs=1M count=64
partprobe $DEV
parted $DEV --script -- mklabel msdos
parted $DEV --script -- mkpart primary fat32 1MiB 100%
mkfs.vfat -F32 ${DEV}1
¶ show extended superblock information of extN partition
debugfs -R stats /dev/VG0/root
¶ mark bad blocks on degrading hard disk with extN
umount /dev/sda1
e2fsck -cc /dev/sda1