Today, I need to update my CentOS servers. So I fire up #yum -y updateIt ends up with error that say "rpm database corrupted"After googling, I get the way to fix it back.To Fix The RPM's Corrupted Database #rm -f /var/lib/rpm/__db*
#rpm --rebuilddb#yum -y updateI hope that this tip may save someone out there. :)
ip add | grep inet ; python -m SimpleHTTPServerThis command will show ip addresses of server. All I need to do is asking my user to open up the browser and type myserver's ipaddress:8000. Now he can download the data on server to his computer easily. I included the screenshot to show you how it looks like in browser.
Question: What is SSH?
Answer: Secure Shell or SSH is a network protocol that allows data to be exchanged using a secure channel between two networked devices
Here is how I utilize this ssh daemon in my daily life.
!)I have 3 intranet servers ( sshgateway, intrawebmail, and winterminal)
!)Firewall is configured so that I can only ssh to sshgateway from external i.e. My Home.
When I need to configure my linux server @ my office from anywhere,
#ssh root@sshgateway.mydomain.net
Ok internet connection is too slow...
#ssh -C –CompressionLevel=9 root@sshgateway.mydomain.net
Oh, I configured my server not to listen on port 22 (default sshd port) for security reason.
#ssh -p 443 root@sshgateway.mydomain.net
I must ssh to intrawebmail to fix some problems,but I can only access to sshgateway.
#ssh -t root@sshgateway.mydomain.net ssh root@intrawebmail
Now I get access to intrawebmail server.
Fixed! I need to check webmail from intrawebmail that is only accessible in office.
#ssh -L 8080:intrawebmail:80 root@sshgateway
1)In firefox, go to Tools>Option>Advanced>Network>Setting
2)In SOCKS host 127.0.0.1 port 8080
Now I can check my office webmail from outside.
How about my winterminal? Is it healthy?
#ssh -L 3389:interminal:3389
1)Now I can remote desktop to 127.0.0.1 that redirect to winterminal.
From public internet hot spot, I want to check my bank account. Network is not secure.
So, I will tunnel my traffic through my office network.(Some may call it "Bypassing Firewall")
#ssh -D 9999 root@sshgateway.mydomain.net
1)In firefox, go to Tools>Option>Advanced>Network>Setting
2)In SOCKS host 127.0.0.1 port 9999
Now my traffic is encrypted and I can check my bank account securely 
One of my friends asks me to help with setting up a linux server. Although I want to help, his server is in Myanmar and I can not ssh to it because it is extremely protected by ISP.
What I do is:
I ask him to ssh to my sshgateway from his highly protected server;
#ssh -R 9999:127.0.0.1:22 root@sshgateway.mydomain.net
Then, on my sshgateway server , I ssh back to his linux server by using:
#ssh -p 9999 root@localhost
Now I can ssh to a host behind NAT and Firewall.
LAST BUT NOT LEAST
Now you know how we can utilize SSH in various ways. But let me remind you that running a ssh host on internet is not as easy as you think.
Believe it or not: everyday I get 5 to 13 report emails from my ssh server that tell
“ Some body is attacking ssh server by using bruteforcing............... and blah blah blah”
If you don't give enough attention to this log messages , somebody may be able to root your server one day. That compromised ssh daemon can even put you into jail.
Don't worry! I will show you how to secure ssh server, but not now. LATER.......
Hope it gives you some knowledge......
netlynker
Q: What is the best remote administration tool for Windows??
A: A car!
tar -tzvf filename.tar.gz | xargs rm -f
"""TONNAGE/PRICE CALCULATOR
========================
AUTHOR = NETLYNKER
LANGUAGE = PYTHON 2.6.5
VERSION = 1.0
"""
from Tkinter import *
from math import *
import tkMessageBox
app = Tk()
app.title("Timber Tonnages/Price Calculator")
app.geometry("410x200+100+100")
#========================================================================
uom = StringVar()
uom.set(None)
option = OptionMenu(app, uom, "Feet", "Inch", "Millimeter")
option.grid(row=1, column=5, padx=5, pady=5)
#========================================================================
l1 = Label(app, text="Length").grid(row=1,column=0, padx=5, pady=5)
l2 = Label(app, text="Width").grid(row=2, column=0, padx=5, pady=5)
l3 = Label(app, text="Height").grid(row=3, column=0, padx=5, pady=5)
l4 = Label(app, text="Quantity").grid(row=4, column=0, padx=5, pady=5)
l5 = Label(app, text="Rate").grid(row=5, column=0, padx=5, pady=5)
l6 = Label(app, text="Measured By").grid(row=1, column=4, padx=5, pady=5)
l7 = Label(app, text="Tons",font="Tahoma").grid(row=4, column=6, padx=5, pady=5)
l8 = Label(app, text="S$",font="Tahoma").grid(row=5, column=6, padx=5, pady=5)
l9 = Label(app, text="Ton:", font="Tahoma").grid(row=4, column=4, padx=5, pady=5)
l10 = Label(app, text="Price: ",font="Tahoma").grid(row=5, column=4, padx=5, pady=5)
#========================================================================
ev1 = StringVar()
e1 = Entry(app, textvariable=ev1)
e1.grid(row=1, column=2, columnspan=2, padx=5, pady=5)
ev2 = StringVar()
e2 = Entry(app, textvariable=ev2)
e2.grid(row=2, column=2, columnspan=2, padx=5, pady=5)
ev3 = StringVar()
e3 = Entry(app, textvariable=ev3)
e3.grid(row=3, column=2, columnspan=2, padx=5, pady=5)
ev4 = StringVar()
e4 = Entry(app, textvariable=ev4)
e4.grid(row=4, column=2, columnspan=2, padx=5, pady=5)
ev5 = StringVar()
e5 = Entry(app, textvariable=ev5)
e5.grid(row=5, column=2, columnspan=2, padx=5, pady=5)
#=========================================================================
def in_to_ton():
global ton
try:
ton = ((float(ev1.get())*float(ev2.get())*float(ev3.get()))/86400)*int(ev4.get())
return ton
except ValueError:
valueerror()
def ft_to_ton():
global ton
try:
ton = ((float(ev1.get())*float(ev2.get())*float(ev3.get()))/7200)*int(ev4.get())
return ton
except ValueError:
valueerror()
def mm_to_ton():
global ton
try:
inc = float(ev1.get())/25.4
ton = ((inc*float(ev2.get())*float(ev3.get()))/86400)*int(ev4.get())
return ton
except ValueError:
valueerror()
def print_one():
global pr, ans
if uom.get() == "Inch":
ans = StringVar()
label = Label(app, textvariable=ans, bg="pink",width=10,font="Tahoma")
label.grid(row=4, column=5)
ans.set(round(in_to_ton(),3))
pr = StringVar()
prlab = Label(app, textvariable=pr, bg="pink",width=10,font="Tahoma")
prlab.grid(row=5, column=5)
pr.set(round(float(ton)*float(ev5.get()),3))
elif uom.get() == "Feet":
ans = StringVar()
label = Label(app, textvariable=ans, bg="pink",width=10,font="Tahoma")
label.grid(row=4, column=5)
ans.set(round(ft_to_ton(),3))
pr = StringVar()
prlab = Label(app, textvariable=pr, bg="pink",width=10,font="Tahoma")
prlab.grid(row=5, column=5)
pr.set(round(float(ton)*float(ev5.get()),3))
elif uom.get() == "Millimeter":
ans = StringVar()
label = Label(app, textvariable=ans, bg="pink",width=10,font="Tahoma")
label.grid(row=4, column=5)
ans.set(round(mm_to_ton(),3))
pr = StringVar()
prlab = Label(app, textvariable=pr, bg="pink",width=10,font="Tahoma")
prlab.grid(row=5, column=5)
pr.set(round(float(ton)*float(ev5.get()),3))
else:
tkMessageBox.showerror("Unit of Measurement","Select UOM(Feet/Inch/Millimeter)")
def reset():
#global e1, e2, e3, e4, e5
e1.delete(0,END)
e2.delete(0,END)
e3.delete(0,END)
e4.delete(0,END)
e5.delete(0,END)
pr.set("")
ans.set("")
def valueerror():
tkMessageBox.showerror("Wrong Value","Value must be numbers")
#=========================================================================
b1 = Button(app, text="Calculate", command=print_one, width=7)
b1.grid(row=7, column=2, padx=5, pady=5)
b2 = Button(app, text="Quit", command=exit, width=7)
b2.grid(row=7, column=3, padx=5, pady=5)
b3 = Button(app, text="Reset", command=reset, width=7)
b3.grid(row=7, column=5, padx=5, pady=5)
#=========================================================================
app.mainloop()
