Linux SysAdmin tricks

Sysadmin_tricks.sh

# network tricks

#identify a network card:
ethtool --identify eth7

#Copy a directory tree without the files:
rsync -a -f"+ */" -f"- *" source/ destination/

#monitor NFS traffic
watch -d "netstat -plaute | grep nfs | sort -k 4,5"

### IO Scheduler settings
# for servers NEVER use cfq. Use either deadline or noop
echo noop > /sys/block/sda/queue/scheduler

# for RAID controllers, use bigger request queues
# try values up to 2048
echo 512 > /sys/block/sda/queue/nr_requests

# for faster sequential performance, try bigger read-ahead
# up to 131072
echo 16384 > /sys/block/sda/queue/read_ahead_kb

###### DANGEROUS COMMANDS ##################
# use the MagicSysRq from an ssh connection
# see /usr/src/linux/Documentation/sysrq.txt
# enable MagicSysRq
echo 1 > /proc/sys/kernel/sysrq

# force disk sync
echo s > /proc/sysrq-trigger

# force reboot
echo b > /proc/sysrq-trigger

# force poweroff
echo o > /proc/sysrq-trigger

##### DESCTRUCTIVE COMMANDS ################
# copy partition table from a disk to 
# another one (for instance to create md RAIDs)
sfdisk -d /dev/sdc | sfdisk /dev/sdd

# clean up all partitions from a disk 
# (say bye bye to all data!)
wipefs -a /dev/sdz