• Whats my WAN IP?

dig +short myip.opendns.com @resolver1.opendns.com

• Find large files, print 10 largest files in dir

find . -printf '%s %p\n'|sort -nr|head

• size of all files older than mtime

find . -mtime +7 -print0 | du -hc --files0-from - | tail -n 1

• To find the largest file in all sub-directories:

find . -type f -exec ls -s {} \; | sort -nr | awk 'NR==1 { $1=""; sub(/^ /, ""); print }'

• grep for valid IP Addresses.

grep -E -o "(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)" file.txt

• show used inode count for subdirectories.

find */ | sed 's!/.*!!' | uniq -c

• free all caches

free && sync && echo 3 > /proc/sys/vm/drop_caches && free

• rescan all SCSI buses

for i in /sys/class/scsi_host/host{0..32}/scan; do echo "- - -" > $i; done

• enlarge LVM

fdisk /dev/sdk
#set partition type to Linux LVM (type 8e)
pvcreate /dev/sdk1
vgextend VolGroupDB /dev/sdk1
lvextend -l +100%FREE /dev/mapper/VolGroupDB-data
resize2fs -p /dev/mapper/VolGroupDB-data
#for xfs use xfs_growfs /dev/mapper/VolGroupDB-data
parted -a optimal /dev/sdc mklabel gpt
parted -a optimal /dev/sdc mkpart p 0% 100%
parted -a optimal /dev/sdc set 1 lvm on
vgextend VGEXL /dev/sdf1
lvresize -l +100%free /dev/mapper/VGEXL-exllv

• Enlarge LVM 2

echo '1' > /sys/class/scsi_disk/0\:0\:3\:0/device/rescan
yum install cloud-utils-growpart
growpart  /dev/sdd 1
pvresize /dev/sdd1
lvextend -l +100%FREE /dev/mapper/VGKUB-lv_kub
xfs_growfs /dev/mapper/VGKUB-lv_kub