How to export and import Oracle schemas, or backup Oracle databases
You can use the exp and imp executables to perform data backup and restoration.
1 -- Export 2 exp <username>/<password>@<server> file=data.dmp consistent=y grants=no statistics=none 3 4 -- Import 5 imp <username>/<password>@<server> file=data.dmp fromuser=<source_username> touser=<username>
Fixing slowdown of X after installing 4Gb of RAM
Both X and 3D acceleration of my Lenovo X61s became horrendously slow after I upgraded to 4Gb of RAM . After a while of Googling I found a thread that explained why it had become slow. In my dmesg I could see the following error, which hinted me to the cause.
1 mtrr: type mismatch for e0000000,10000000 old: write-back new: write-combining
I want to emphasize that I’m not the author of this script. But I want to store it here because forums and topics sometimes disappear. The original author seems to be “hubick” of the thread linked above. For me this script was plug & play, so many props to the original author if you happen to read this ;) I just needed to run it before X was started.
1 #!/bin/sh 2 # Fixup /proc/mtrr 3 # 4 # chkconfig: 12345 0 99 5 # description: Fixup /proc/mtrr 6 # 7 # Save this file as /etc/init.d/mtrrfixup and 8 # use "chkconfig --add mtrrfixup" 9 # to have this script run by init when the system starts. 10 # 11 # The default mtrr table after boot looks like the following: 12 # reg00: base=0xd8000000 (3456MB), size= 128MB: uncachable, count=1 13 # reg01: base=0xe0000000 (3584MB), size= 512MB: uncachable, count=1 14 # reg02: base=0x00000000 ( 0MB), size=4096MB: write-back, count=1 15 # reg03: base=0x100000000 (4096MB), size= 512MB: write-back, count=1 16 # reg04: base=0x120000000 (4608MB), size= 128MB: write-back, count=1 17 # reg05: base=0xd7f80000 (3455MB), size= 512KB: uncachable, count=1 18 # 19 # The main problem is entry 1, which covers 20 # the AGP aperature and Video Card memory. 21 # Being present and uncachable, it prevents 22 # the fglrx driver module from using/creating a 23 # write-combined region for the video card. 24 # The second problem is entry 2, covering all 25 # our ram, which prevents us from creating 26 # any new sections which aren't uncachable. 27 # 28 # We have a maximum of 7 mtrr registers. 29 # All sizes must be a power of two. 30 # The start and end of any page must 31 # have the same 'upper bits'. 32 33 # First remove all existing values... 34 # Order matters - wrong order locks system hard! 35 echo "disable=2" >| /proc/mtrr 36 echo "disable=5" >| /proc/mtrr 37 echo "disable=1" >| /proc/mtrr 38 echo "disable=3" >| /proc/mtrr 39 echo "disable=4" >| /proc/mtrr 40 echo "disable=0" >| /proc/mtrr 41 42 # Now create the right ones... 43 44 # Main Memory: 0-2048,2048-3072,3072-3328,3328-3456 45 # These are powers of two, they get progressively smaller 46 # so we can get right up to the system device page below. 47 echo "base=0x00000000 size=0x80000000 type=write-back" >| /proc/mtrr 48 echo "base=0x80000000 size=0x40000000 type=write-back" >| /proc/mtrr 49 echo "base=0xC0000000 size=0x10000000 type=write-back" >| /proc/mtrr 50 echo "base=0xD0000000 size=0x08000000 type=write-back" >| /proc/mtrr 51 52 # System Devices: 3456-3584 53 echo "base=0xD8000000 size=0x08000000 type=uncachable" >| /proc/mtrr 54 55 # AGP Aperature: 3584-3712 56 echo "base=0xE0000000 size=0x08000000 type=write-combining" >| /proc/mtrr 57 58 # Video Card: 3712-3840 59 echo "base=0xE8000000 size=0x08000000 type=write-combining" >| /proc/mtrr 60 61 # High memory area: 4096-5096 62 echo "base=0x100000000 size=0x40000000 type=write-back" >| /proc/mtrr
Disable javascript resizing of Firefox
There is absolutely not a single developer in the world who knows what size I like my browser, although many people think they do. To prevent resizing of FF make the following steps.
- Open browser preferences
- Choose “Content”
- Choose “Advanced” on the “Enable javascript” preference
- Untick “Move or resize existing windows”
Limiting scp bandwidth usage
Use the -l parameter of scp to limit the speed of a file transfer (both upload or download). An empirically tested, good value for a 54Mbit wireless connection is 18000:
1 scp -l 18000 remotehost:file.img .
SSH public key encryption - How to generate the key and how to copy it to the remote machine
1 ssh-keygen -t dsa 2 ssh-copy-id -i ~/.ssh/id_dsa.pub user@server
OS X doesn’t come equipped with ssh-copy-id but you can download the script from here.