26. How to print line numbers of each output line of a text file ?
# cat -n yourfile.txt
27. How to negate a grep result?
# grep -v "null" yourfilename
28. How to list statistics from your network ?
# netstat -s
29. What is the country code for a particular country ?
# grep -i philippines /usr/share/zoneinfo/iso3166.tab
30. How to find out who owns and manages a particular domain ?
# whois google.com
31. How to get the resolved IP of a domain ?
# nslookup google.com
# host google.com
# dig google.com
32. How to say hello and goodbye to your system log file ?
# logger 'Hello and Goodbye'
33. How to list out all your USB current connections ?
# lsusb -v
34. How to list out all your PCI card connections ?
# lspci -v
35. How to lock/unlock a bash enabled user shell account ?
# passwd -l useraccount
# passwd -u useraccount
# passwd -S useraccount
36. How to limit and change available shell accounts for user's shell assignment ?
# vi /etc/shells
37. How to change the default values when adding new user accounts ?
# vi /etc/default/useradd
38. How to create default files automatically every time a new user accounts is created ?
# cp /home/pinoy/whateverfile.txt /etc/skel
# useradd -d /home/newuser newuser
39. How to go the easy way to home folder of a particular user if you have multinested virtual home folders?
# cd ~hisusername
40. How to browse and download the whole pages of a particular WWW site in one shot ?
# wget -p --progress=dot http://www.google.com
41. How to safely mark badblocks from another ext2/ext3 linux harddisk ?
# umount /dev/other-harddisk2
# e2fsck -c /dev/other-harddisk2
42. How to create a new ext3 filesytem with bad-block checking from your secondary harddisk?
# mkfs.ext3 -c /dev/other-harddisk2
43. How to compare bzip2 compressed files ?
# bzdiff file1 file2
44. How to detect hardware monitoring chips and load modules related to newly detected chips?
>45. How to know if your postfix or sendmail is running ?
# ps axuw | grep sendmail
# ps axuw | grep postfix
46. How to change the default port when spamassassin is launched?
# vi /etc/sysconfig/spamassassin
47. How to disable postfix permanently after reboot ?
# chkconfig --levels 345 postfix off
48. How to know the number of children spawned by apache ?
# ps axuw | grep http | wc -l
49. How to avoid a module from being loaded by kernel during startup and blacklist it permanently?
# vi /etc/modprobe.d/blacklist
50. How to quickly count all your queued mail when you box is really hogging due to spam bruteforce attacks and spam mailer?
# mailq | wc -l
How to smile ?