System backup

• Transfer all the files to the new partition

  rsync -aAXvHS --exclude={"/dev/*","/proc/*","/sys/*","/tmp/*","/run/*","/mnt/*","/media/*","/lost+found","/data"} /* /mnt/backup/
  

• Get the UUID for the new partition

  [root@archie /]# blkid /dev/sda2 
  /dev/sda2: UUID="ca2f7146-122f-4746-8725-7aeb4ca792e6" TYPE="ext4" PARTUUID="48c724bf-02"
  

• Edit mountpoints

  [root@archie /]# vim /etc/fstab
  

• Edit the new system's boot configuration

  [root@archie /]# vim /mnt/backup/boot/syslinux/syslinux.cfg
  

• Enter the new system and fix booting

  [root@archie /]# arch-chroot /mnt/backup/
  sh-4.3# syslinux-install_update -i -a -m
  Syslinux BIOS install successful
  Boot Flag Set - /dev/sda2
  Installed MBR (/usr/lib/syslinux/bios/mbr.bin) to /dev/sda
  

Burning Blu Ray Discs

Look at this blog
For mkudffs, see arch: udftools

What I get is

24712708096/25000000000 (98.9%) @0.9x, remaining 1:08 RBU 100.0% UBU  76.6%
24726929408/25000000000 (98.9%) @0.9x, remaining 1:04 RBU 100.0% UBU  79.7%
24741150720/25000000000 (99.0%) @0.9x, remaining 1:01 RBU 100.0% UBU  85.9%
24755372032/25000000000 (99.0%) @0.9x, remaining 0:58 RBU 100.0% UBU  73.4%
:-[ WRITE@LBA=b87400h failed with SK=5h/END OF USER AREA ENCOUNTERED ON THIS TRACK]: Input/output error
:-( write failed: Input/output error
/dev/sr2: flushing cache
/dev/sr2: closing track
/dev/sr2: closing session
:-[ CLOSE SESSION failed with SK=5h/INVALID FIELD IN CDB]: Input/output error
/dev/sr2: reloading tray

Ubuntu - Update hostname from DHCP

This script is basically a mutation of the script found in drwindsor's post :

#!/bin/sh
# Filename:     /etc/dhcp/dhclient-exit-hooks.d/hostname
# Purpose:      Used by dhclient-script to set the hostname of the system
#               to match the DNS information for the host as provided by
#               DHCP.
#

if [ "$reason" != BOUND ] && [ "$reason" != RENEW ] \
   && [ "$reason" != REBIND ] && [ "$reason" != REBOOT ]
then
        return
fi

echo dhclient-exit-hooks.d/hostname: Dynamic IP address = $new_ip_address
hostname=$(host $new_ip_address | cut -d ' ' -f 5 | cut -d "." -f 1)
echo $hostname > /etc/hostname
hostname $hostname
echo dhclient-exit-hooks.d/hostname: Dynamic Hostname = $hostname

Git mirror without cloning

What I want to do is to set up a bare mirror git repository without fetching the changes. It should be a fast operation compared to:

git clone --mirror $REPOURL

Here are the steps that I did to achieve the same results as a full clone:

# Create and update with the clone command
git clone --mirror https://github.com/matelakat/vimide vimide-with-clone
cd vimide-with-clone/
git fetch
cd ..

And let's create the equivalent:

git init --bare vimide-manual
cd vimide-manual
git remote add --mirror origin https://github.com/matelakat/vimide
git fetch
git pack-refs --all --prune
cd ..

You can see that the two directories are the same:

diff -r vimide-with-clone/ vimide-manual/ && echo "ALL the same"

ALL the same

Differences between git branches

The problem

Given I have two branches, A and B within a git repository, I would like to come up with two sets of changes: (A-B) and (B-A). So I would like to find all the commits that are in A but not in B, and vice versa.

Introducing the same change to two branches

Let's set up a git repository to play with. As a first step, I create an initial commit, with only one file in it, a simple greeting:

$ git init
$ echo "hello there" > hello.txt
$ git add hello.txt
$ git commit -m "Initial commit"

And now, make the branching, and introduce the same change to each of those branches:

$ git checkout -b A
$ echo "blah" > blah.txt
$ git add blah.txt
$ git commit -m "Added blah"

And see the B branch:

$ git checkout master -b B
$ echo "blah" > blah.txt
$ git add blah.txt
$ git commit -m "Added blah"

See if git is smart enough to find out that the two changes are the same:

$ git log A..B --oneline | wc -l

1

Of course, they are not the same, they are copies of the other. So let's see the other command, called git-cherry:

$ git cherry A B

This shows only one line, with a minus sign. From the documentation of git cherry:

git cherry [-v] [<upstream> [<head> [<limit>]]]

       Every commit that doesn’t exist in the <upstream> branch has its id (sha1) reported,
       prefixed by a symbol. The ones that have equivalent change already in the <upstream>
       branch are prefixed with a minus (-) sign, and those that only exist in the <head>
       branch are prefixed with a plus (+) symbol:

SSD - Bytes written

I Have an Intel 520 SSD. I can use smartmontools to ask how much bytes have been written to it:

sudo ./smartctl -q noserial -i -l devstat,0 -l devstat /dev/sda

smartctl 6.2 2013-07-26 r3841 [x86_64-linux-3.2.0-32-generic] (local build)
Copyright (C) 2002-13, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF INFORMATION SECTION ===
Model Family:     Intel 520 Series SSDs
Device Model:     INTEL SSDSC2CW240A3
Firmware Version: 400i
User Capacity:    240,057,409,536 bytes [240 GB]
Sector Size:      512 bytes logical/physical
Rotation Rate:    Solid State Device
Device is:        In smartctl database [for details use: -P show]
ATA Version is:   ACS-2 T13/2015-D revision 3
SATA Version is:  SATA 3.0, 3.0 Gb/s (current: 3.0 Gb/s)
Local Time is:    Sat Jun 21 08:42:06 2014 BST
SMART support is: Available - device has SMART capability.
SMART support is: Enabled

Device Statistics (GP Log 0x04) supported pages
Page Description
  0  List of supported log pages
  1  General Statistics
  4  General Errors Statistics
  6  Transport Statistics
  7  Solid State Device Statistics

Device Statistics (GP Log 0x04)
Page Offset Size         Value  Description
  1  =====  =                =  == General Statistics (rev 2) ==
  1  0x008  4             1129  Lifetime Power-On Resets
  1  0x010  4             8660  Power-on Hours
  1  0x018  6       5401949881  Logical Sectors Written
  1  0x028  6       5794864033  Logical Sectors Read
  4  =====  =                =  == General Errors Statistics (rev 1) ==
  4  0x008  4                0  Number of Reported Uncorrectable Errors
  4  0x010  4             9232  Resets Between Cmd Acceptance and Completion
  6  =====  =                =  == Transport Statistics (rev 1) ==
  6  0x008  4             9232  Number of Hardware Resets
  6  0x010  4             4085  Number of ASR Events
  6  0x018  4                0  Number of Interface CRC Errors
  7  =====  =                =  == Solid State Device Statistics (rev 1) ==
  7  0x008  1              255  Percentage Used Endurance Indicator

Recording terminal sessions

During the weekend I was experimenting with some tools to record terminal sessions. The result of the hacking:

• ttyrec
• ttygif