Git Cheat Sheet

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Creating a new repository

$ mkdir project
$ cd project
$ git init
$ git remote add origin git@github.com:yourlogin/your-repo.git
$ git add .
$ git commit -am “new repository”
$ git push -u origin master

Cloning existing repository

$ git clone https://github.com/username/your-repo.git

Creating branch

$ git checkout -b feature-1 Read More ...

CategoriesOS

x11vnc and Dummy Monitor

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Setup x11vnc

Install package:

$ apt install x11vnc

Set password:

$ x11vnc -storepasswd /etc/x11vnc.pass

Create x11vnc service:

$ vim /lib/systemd/system/x11vnc.service
[Unit]
Description=Start x11vnc at startup.
After=multi-user.target
[Service]
Type=simple
ExecStart=/usr/bin/x11vnc -auth guess -forever -loop -noxdamage -repeat -rfbauth /etc/x11vnc.pass -rfbport 5900 -shared
[Install]
WantedBy=multi-user.target

Enable the service:

$ systemctl enable x11vnc.service 
$ systemctl daemon-reload

Reboot.

Setup Dummy Monitor Driver

Install package:

$ apt install xserver-xorg-video-dummy

Configure xorg.conf:

$ vim /etc/X11/xorg.conf
Section "Device"
  Identifier  "Configured Video Device"
  Driver      "dummy"
EndSection

Section "Monitor"
  Identifier "Configured Monitor"
  HorizSync 31.5-48.5
  VertRefresh 50-70
EndSection

Section "Screen"
  Identifier "Default Screen"
  Monitor "Configured Monitor"
  Device "Configured Video Device"
  DefaultDepth 24
  SubSection "Display"
    Depth 24
    Modes "1920x1080"
  EndSubSection
EndSection

Java 9 Restriction on MD5withRSA

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Problem:
You got the following error message when trying to access Java applet.

Unsigned application requesting unrestricted access to system. The following resource is signed with a weak signature algorithm MD5withRSA and is treated as unsigned.

Screen Shot 2017-10-30 at 5.22.09 PM

Workaround:

  1. Get java.security file in Java Applet Plugin folder.
$ cd /Library/Internet\ Plug-Ins/JavaAppletPlugin.plugin/Contents/Home/conf/security/ 
$ vim java.security
  1. Find the following lines and comment them out.
jdk.certpath.disabledAlgorithms=MD2, MD5, SHA1 jdkCA & usage TLSServer, \
 RSA keySize < 1024, DSA keySize < 1024, EC keySize < 224

jdk.jar.disabledAlgorithms=MD2, MD5, RSA keySize < 1024, \
      DSA keySize < 1024

jdk.tls.disabledAlgorithms=SSLv3, RC4, MD5withRSA, DH keySize < 1024, \
    EC keySize < 224

E.g.:

#jdk.certpath.disabledAlgorithms=MD2, MD5, SHA1 jdkCA & usage TLSServer, \
# RSA keySize < 1024, DSA keySize < 1024, EC keySize < 224

#jdk.jar.disabledAlgorithms=MD2, MD5, RSA keySize < 1024, \
#      DSA keySize < 1024

#jdk.tls.disabledAlgorithms=SSLv3, RC4, MD5withRSA, DH keySize < 1024, \
#    EC keySize < 224

Bright Cluster – HA Setup

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  1. Configure failover interface in 1st Head Node
  2. Register license for HA
  3. Prepare HA configuration using command 
     $ cmha-setup
  4. Go to Setup menu to prepare configuration
  5. Check Clone Failover for clone instruction
  6. Power-on second head node, let it boot to PXE
  7. Select Rescue in PXE menu
  8. Login as root
  9. Start cloning by calling 
     $ /cm/cm-clone-install --failover
  10. The second head node will reboot automatically once completed
  11. Back to primary head node.
  12. In cmha-setup menu, select Finalize.
  13. Verify HA status 
     $ cmha status
  14. In cmha-setup menu, configure shared storage.

 

Reverse SSH

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Tested on CentOS, but should be applicable on Ubuntu as well.

  1. Add Epel repo, https://www.tecmint.com/how-to-enable-epel-repository-for-rhel-centos-6-5/
  2. Install autossh 
     $ yum install autossh
  3. Run autossh command with the following format 
     $ autossh -M -fN <login@remoteserver> -R :localhost:22
 
 E.g.:
 $ autossh -M 20000 -fN support@remote.com -R 12021:localhost:22

EGO issue in IBM SCF CE

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Problem:

[root@pcmce-co68 ~]# egosh resource list
Cannot get host info. Not logged on.

Solution:
Log in to egosh shell (one time only). Default user and password is Admin.

[root@pcmce-co68 ~]# egosh user logon
user account: Admin
password:
Logged on successfully
[root@pcmce-co68 ~]# egosh resource list
NAME status mem swp tmp ut it pg r1m r15s r15m ls
pcmce-c* ok 827M 1516M 69G 7% 258 3.1 0.2 3.3 0.7 1

 

Disable Serial Console Redirection in xCAT

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PXE boot config:

"... console=tty0 console=ttyS0,115200 ..."

Note: serial console redirection is managed by hardware profile.

To check hardware profile:

$ tabdump nodehm
#node,power,mgt,cons,termserver,termport,conserver,serialport,serialspeed,serialflow,getmac,cmdmapping,consoleondemand,comments,disable
"__HardwareProfile_IPMI",,"ipmi",,,,,,,,,"/opt/pcm/etc/hwmgt/mappings/HWCmdMapping_ipmi.xml",,,
"__HardwareProfile_IBM_Flex_System_x",,"ipmi",,,,,"0","115200","hard",,"/opt/pcm/etc/hwmgt/mappings/HWCmdMapping_flex_x.xml",,,
"__HardwareProfile_IBM_System_x_M4",,"ipmi",,,,,"0","115200","hard",,"/opt/pcm/etc/hwmgt/mappings/HWCmdMapping_rackmount_x.xml",,,
"__HardwareProfile_IBM_iDataPlex_M4",,"ipmi",,,,,"0","115200","hard",,"/opt/pcm/etc/hwmgt/mappings/HWCmdMapping_rackmount_x.xml",,,
"__HardwareProfile_IBM_NeXtScale_M4",,"ipmi",,,,,"0","115200","hard",,"/opt/pcm/etc/hwmgt/mappings/HWCmdMapping_nextscale_x.xml",,,
"__Chassis_IBM_Flex_chassis",,"blade",,,,,,,,,,,,

To disable: clear the entries of serialport, serialspeed and serialflow columns

$ chdef -t group -o __HardwareProfile_IBM_Flex_System_x serialport= serialspeed= serialflow=