desktop environment

keyboard oriented settings

it's highly recommended to use ratpoison or stumpwm. However, the following should work on any desktop environment (e.g. Gnome and KDE)

  • tools used
    • xwrits - reminds you to take wrist breaks well, in case you don't have workrave or RSIBreak
    • xbindkeys - a grabbing keys program for X can be used to define combination keys that simulate behaviors of ratpoison
    • dmenu - dynamic menu (includes dmenurun, and dmenupath) open program through keystrokes
    • xmodmap - utility for modifying keymaps and pointer button mappings in X emacs key (make enter and cap ctrls)
  • configurations

    NOTE: GNU Guile is required to configure xbindkeys

    keyoriented

sharing files through bluetooth

  • In GNOME 3 (< 3.6) use this command gnome-file-share-properties to configure file sharing settings. (Or with Gnome shell, you can search it in Activities overview.)
  • Above GNOME 3.6

    The above mentioned tool has been removed from gnome-user-share package, and the related dconf keys have also been changed. Some sharing properties can be set in G-C-C now but some functionality seems to be missing.

applications

vmware

  • VMware 7.1.4(5) on Ubuntu 11.10

    fix module compilation errors

    • within the following directory, usually run scripts within 'vmware2639patchv3.tar.bz2' is enough
    • other web pages serve as references.

    references & patches: vmware-7-ubuntu11.10-patch.dir

ubuntu

offline repo

all related files are in offlineubunturepo

  • preparation
    1. define an offline repo location add it to the top of the source list deb file:///opt/ubuntu_offline_repo/ oneiric main restricted multiverse universe
    2. populate the above directory
      • the key here is to simulate the file system hierarchy of an ubuntu mirror
      • download files with 'initsetup.bat'
      • copy to corresponding directory in the local repo
      • apt-get update
    3. the local repo is ready to be used, searched and generate dependencies.
  • how to use
    1. copy files in inlinux to the local repo (or other places e.g. root)
    2. you can accumulate the package to install to a separate file. (find them through apt-cache search) the 'todo.txt' is and example
    3. run ./genlist.sh to generate aptlist (see ./genlist.sh to see usage)
    4. copy aptlist to pen disk to windows box with Internet
    5. run wget.exe -i apt_list to download
    6. copy all deb files downloaded to /var/cache/apt/archives/
    7. apt-get install <packages>

shell commands

remove some files but not all

  • shell pattern (glob and extglob)
    • basic glob ?: one char; *: any number of chars; [..]: one of the char

      highly limited, trying to figure out the right pattern might be even harder and more time consuming than the toolchain method

    • extglob shopt -s extglob

      !(.|.|.) anything that doesn't match patterns

  • toolchain

    one example: ls | grep … | xargs rm

urxvt

The following command, combined with new-session in ~/.tmux.conf, let you connect to an existent session or create a new one if no session is alive.

urxvt -title "urxvt-tmux" -e tmux attach-session &

rsync

rsync -avuz --exclude=.repo/ --exclude=.git/ `pwd` dev-tplink:
rsync -avuz dev-tplink:/home/xiongchao/gingerbread_u12/out .

# to windows: pay attention to the last slash of the 1st param.
rsync --delete -vuzr carlibrelib ~/mnt/syncdisk

ssh

sshfs

sshfsintro

speed/multiplex up ssh connection

articles: sshconnectionmultiplexing

  • ssh -N -f host

    opens a connection and goes into the background without executing a remote command so you don't need to keep a window or shell running locally just to keep that connection.

  • opinions

    Also, isn't the whole point of putting ControlPath in .ssh/config to make the -S argument uneccessary? And doesn't the ControlMaster auto also make the toggling -M uneccessary?

  • auto vs autoask

    You can set it to autoask instead of auto to have ssh prompt you for whether or not to reuse an existing connection.

  • ControlPath

    The configuration directive ControlPath tells ssh where it should keep its socket information. I've chosen to put these files in /tmp, however it may be best to put this into your own home directory on multi-user systems.

  • -o ControlMaster=no for ssh tunneling

    NOTE: You will need to specify -o ControlMaster=no when using ssh to do ssh tunneling otherwise multiple tunnels to a particular host will not work.

  • X11 forwarding under connection multiplexing

    Won't work and will fail silently, use -v to see whether X11 forwarding request is sent to debug this.

    • config solution 
      add ForwardX11=yes (and ForwardX11Trusted=yes) to .ssh/config
    • -S none option

      The last time I checked this one, it's not working, however it should according to ssh man page.

      PS: while testing this one, I crashed systemd in SLED12 beta2, which resulted in very interesting bug.

diff + patch

two files both added some lines, but no change among common lines

example:

diff -Naur index/ ~/icwiki/index/ > icwiki-patch.diff

patch -Rp0 --merge < ~/learnspace/git-mylife/icwiki/icwiki-patch.diff

NOTE: you can –dry-run for previous command to see what the effect might be, however, you are still encouraged to backup your to-be-patched files.

mount virtual disk

original reference: How to mount a VirtualBox VDI image | Be the signal

The following the essential steps needed 

# you need to be root
## max_part is needed, as sometimes it defaults to 0
modprobe nbd max_part=16

# nbd0 is established by last cmd
qemu-nbd -c /dev/nbd0 .VirtualBox/Machines/win_xp/LargeData.vdi

mount /dev/mbd0p1 /mnt/tmp

Multiple Pipes

Common Grep Buffer Issue

use --line-buffered, a GNU grep extension.

  • example adb shell 'getevent /dev/input/event4' | grep --line-buffered "0003 0019" | tee tmp.txt

Other Stdout Buffer Issue

use complex while-read-line structure.

  • example tail -f logfile | while read line ; do echo "$line"| grep 'org.springframework'|cut -c 25- ; done

Timestamp output

usually we want to timestamp the output, use Perl to do this.

NOTE: you may need to deal with buffer issues, refer to Multiple Pipes.

  • example The following timestamp the distance sensor's output. 
    # This this the one line perl to timestamp the output.
# You can change `time' to `localtime', if you want pretty time format.
# perl -ne '$|=1; print "[" . time . "]" . ": $_"'

adb shell 'getevent /dev/input/event4' \
    | grep --line-buffered "0003 0019" \
    | perl -ne '$|=1; print "[" . time . "]" . ": $_"'

# relative time, the start of recording is the time zero.
adb logcat | perl -ne \
    '$|=1; $start = time unless $start; print "[" . (time - $start) . "]" . ": $_"'

Swap file

  • use file as swap space. 
    # create a 4G swap image
dd if=/dev/zero of=swap.img bs=1024M count=4
mkswap swap.img

# see the currently used swap space
swapon -s

# mount this file as swap space
swapon swap.img

    Optionally you can use swapoff to disable some swap space.

  • add this entry into /etc/fstab 
    /opt/swap.img  none            swap    defaults        0       0

tar + 7z

How to backup linux files with 7z 

tar cf - <dir/file> | 7z a -si <path_to_archive_file>

Cool one-line find

  • Finding number of files in a folder 
    find . -type f | wc -l
  • Finding # of all subfolders with a folder 
    find . -type d | wc -l
  • Find # of folders ONLY in current folder 
    find . -maxdepth 1 -type d | wc -l

Cron/Time Management

A thorough article about almost every practical facets of cron and other time management in Linux. Original link

Archived Time - Create, Read, Store, Manipulate.maff

Tmux

Tmux is a very versatile terminal multiplexer.

Fedora/SuSe

Build packages from Sources RPM

You need to install rpmbuild.

rpmbuild –rebuild package_name.src.rpm

rpm -Uvih your_rpm_package.rpm

Optionally, SuSEconfig

Unpacking/Extracting source rpm

rpm2cpio foo-1.0-1.src.rpm | cpio --extract --make-directories --verbose

Restore/Undeleted deleted/overwritten files

testdisk

This is a tool mainly for partition fixing, however, the built-in file restoring function has come to handy a lot of times.

Particularly good for case: you know the position of the file and there is no same-named file under the same path (i.e. doesn't work for overwritten files). This tool recovers the file by looking at the file system journal.

photorec

The more powerful tool coming from the same developer team. This tool bypasses the file system, recovers files by looking at the content instead. This is the best shot for overwritten files.

NOTE: Many on web says that you can't recover overwritten files. The fact is if the blocks of the files are overwritten then you are out of luck, but for files, usually overwriting leaves the old one intact by storing new content in new blocks.

Other "bizarre" ways

grep, debugfs and blablabla…. They work by principle and look awesome, BUT it's hard to use them.

Debug offlineimap error

In my workplace, offlineimap fails to retrieve mails from the company mail sever sometimes.

With the following error: 

Folder INBOX [acc: cxiongsuse]:
 Copy message 13095 (1 of 84) cxiongsuse_remote:INBOX -> cxiongsuse_local
 Copy message 13096 (2 of 84) cxiongsuse_remote:INBOX -> cxiongsuse_local
Copy message from cxiongsuse_remote:INBOX:
 Establishing connection to imap.novell.com:993
 ERROR: command: UID => no response after 60.0 secs
 Establishing connection to imap.novell.com:993
 ERROR: command: UID => no response after 60.0 secs
 ERROR: command: UID => no response after 60.0 secs
Folder INBOX [acc: cxiongsuse]:
 Copy message 13097 (3 of 84) cxiongsuse_remote:INBOX -> cxiongsuse_local
Thread 'Copy message from cxiongsuse_remote:INBOX' terminated with exception:
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/offlineimap/threadutil.py", line 156, in run
    Thread.run(self)
  File "/usr/lib64/python2.7/threading.py", line 504, in run
    self.__target(*self.__args, **self.__kwargs)
  File "/usr/lib/python2.7/site-packages/offlineimap/folder/Base.py", line 330, in copymessageto
    message = self.getmessage(uid)
  File "/usr/lib/python2.7/site-packages/offlineimap/folder/IMAP.py", line 225, in getmessage
    raise e
abort: command: UID => no response after 60.0 secs


Last 3 debug messages logged for Copy message from cxiongsuse_remote:INBOX prior to exception:
thread: Register new thread 'Copy message from cxiongsuse_remote:INBOX' (account 'cxiongsuse')
imap: Attempting plain authentication
imap: Attempting plain authentication
ERROR: Exceptions occurred during the run!
ERROR: command: UID => no response after 60.0 secs
ERROR: command: UID => no response after 60.0 secs
ERROR: command: UID => no response after 60.0 secs

This article tries to explain a way to "fix" this, well not really a fix but a workaround.

  1. The "Copy" lines before errors identify the possible error message.
  2. Find the last successfully archived mail

    In the case above, 13095 and 13096 are the suspicious mails ID. Search the local offlineimap mailbox for these two IDs. If you can't find it, use 13094, i.e. an even earlier one. After all, with an error close, the writing operation might simply fail.

  3. Find another way to log into your mail account.

    Web UI, another Web clients and etc.

  4. Locate the mail you find in step 2.

    Sort all your mail from latest to oldest. And look at the source of the mail in step 2, use "Date" to locate it. Pay attention to the time zone setting. Let's denote the mail you found "2R".

  5. Remove one or more later mail(s) after "2R".

    This would usually solve the problem. Later on, we might try to find out what's wrong with the "bad" mails.


∎

Tags
Comment: Github Issue