You can create a directory tree using just one command in Linux

mkdir -p /tmp/dir1/dir2

Show files and directory containing numbers

ls *[0-9]*

I run this command when I go for lunch or something - these commands take a while to run.

sudo /bin/bash /usr/sbin/makewhatis -w; sudo /usr/bin/updatedb; sudo /home/binnyva/Software/System/chkrootkit-0.47/chkrootkit

This command shows the kernel modules that are currently loaded.

# lsmod

Module                  Size  Used by
vboxdrv                55088  0
autofs4                20421  2
ipt_MASQUERADE          6721  1
iptable_nat             9669  1
nf_nat                 18669  2 ipt_MASQUERADE,iptable_nat
nf_conntrack_ipv4      11717  2 iptable_nat
nf_conntrack           51977  4 ipt_MASQUERADE,iptable_nat,nf_nat,nf_conntrack_ipv4
....

du shows the ‘disk usage’ - the space taken up by the files and folders in the current directory.

du -bh | more

free gives the Memory info (in kilobytes).

free
#Output
             total       used       free     shared    buffers     cached
Mem:       2075000     667508    1407492          0      25988     352076
-/+ buffers/cache:     289444    1785556
Swap:       979924          0     979924

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The last command shows a history of logins…

last

System info about a user. Try: finger root. An admin needs it all the time

finger user_name

#finger root
Login: root                             Name: root
Directory: /root                        Shell: /bin/bash
Last login Tue Nov 27 20:19 (IST) on tty1
No mail.
No Plan.

This will let you run a linux command based on the success of anther command. Note: This will only work in bash shell.

ruby Create_PDF.rb && if [ $? == 0 ]; then kpdf report.pdf; fi

A Linux command to sort the contests of a file

sort file.ext

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