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The slides from a hands on lab given on Software Freedom Day on the 31 August 2013 at the University of the Witwatersrand. It was aimed at showing some of the lesser know features of well known commands as well as some lesser known, yet powerful and command line tools
26/09/2013 Secrets of a Linux Ninja - SFD 2013 Johannesburg, South Africa
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SECRETS OF A LINUX NINJA
Created by / Mark Clarke @mxc4
26/09/2013 Secrets of a Linux Ninja - SFD 2013 Johannesburg, South Africa
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LESSON 1: SSH! A NINJA IS SILENT!
26/09/2013 Secrets of a Linux Ninja - SFD 2013 Johannesburg, South Africa
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Access lan based services via incoming SSH access,Get external SSH access even if its not enabled,Forward X sessions over SSH,Bypass web proxy restrictions
“Take things as they are. Punch when you have to punch. Kickwhen you have to kick.”
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LAB SET UP
Micro-server represents lan. Laptop virtual machine represents external host. Laptop hostmachine is gateway
Lan Net:192.168.1.0/24External Net:192.168.122.0/24Gateway:192.168.1.4/192.168.122.1Lan Host:192.168.1.3External Host:192.168.122.192
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ACCESS A LAN BASED SERVICE WITH INCOMING SSHACCESS
Scenario:
You have ssh access to the lan but no VPN access,You need to access a web application running on the lan.Web App: http://192.168.1.3/ninja.html
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GET EXTERNAL SSH ACCESS EVEN IF ITS NOT ENABLED
Scenario:
You have no external ssh access to networkYou can connect to external ssh servers from the lan
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FORWARD X SESSIONS OVER SSH
Scenario:
XDMCP is disabled,You have SSH access,XForwarding is enabled in sshd config file,
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BYPASS WEB PROXY RESTRICTIONS
Scenario:
Your offices uses a web proxy which restricts traffic to sites with vital information,You have external SSH access,
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LESSON 2: NINJA MOVES
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Transferring files over SSHResuming partial transfers over SSHMounting a share over SSHTransferring files with netcat
“Do not pray for an easy life, pray for the strength to endure adifficult one.”
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TRANSFERRING FILES OVER SSH
Scenario:
You have no ftp/NFS/Samba share access on the server.You need to copy over a file.You have SSH access.
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RESUMING PARTIAL TRANSFERS OVER SSH
Scenario:
You are using scp to copy files,Your download 60 minute download interrupts after 40 minutes and you want toresume.
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MOUNTING A SHARE OVER SSH
Scenario:
You want to mount a remote folder on a server,You have no share access,Only have SSH access
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TRANSFERRING FILES WITH NETCAT
Scenario:
You need to transfer a file and have no SSH access.
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LESSON 3: A NINJA OBSERVES
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Monitoring disks for signs of failureCommand line tools: iotop,vmstat,iostat,psacct
“I fear not the man who has practiced 10,000 kicks once, but Ifear the man who has practiced one kick 10,000 times.”
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MONITORING DISKS FOR SIGNS OF FAILURE
Scenario:
You know your disks will fail. You just don't know when.Use smartctl to monitor your disks.
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COMMAND LINE TOOLS
Scenario:
What process is grinding your disks? - iotopWhere is the bottle neck - disk io, memory or network - vmstatWhich user or system account is using all your resources - psacctYour server crashes and you don't know why - sar
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LESSON 4: A CLEAN KILL
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Using regular expressions to killWho is preventing you from unmounting a block device?
“Take things as they are. Punch when you have to punch. Kickwhen you have to kick.”
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USING REGULAR EXPRESSIONS TO KILL
Scenario:
You have a process to kill often and it a mission to get its pid all the timepkillkillall -r
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WHO IS PREVENTING YOU FROM UNMOUNTING A BLOCKDEVICE?
Scenario:
You trying to unmount a device but you can't because a process/user is accessing itfuser
