shell PS1 terminal escape sequence in linux

If you've seen string like this "\[\e[1;33m\]" in someone's PS1 (bash prompt) value, you may be curious about what it means. Or you may be using it, but not really know what it means (e.g. just copied and pasted from another bash config file). The format is weird. Isn't it?

PS1 bash prompt

run "man bash", search for PROMPTING, you will see that

1. \[  begin a sequence of non-printing characters, which could be used to embed a terminal control sequence into the prompt
2. \]  end a sequence of non-printing characters

You may wonder what "terminal control sequence" is. Generally "terminal control sequence" controls how the data and/or presentation maintained by terminal will be changed (e.g. move cursor, change color, delete line).

ECMA-48

The "terminal control sequence" is defined in ECMA-48 spec [1]. Here I will be focused on only one commonly used terminal control sequence called SGR (the detail is on page 75 of the pdf file, or page 61 of the spec content). SGR controls many graphics aspect of terminal display.

SGR - Select Graphic Rendition. You can think it as just a function which takes some parameters. We need to represent/serialize it so that it can be transferred and interpreted by terminal, etc. Its representation in the spec is "CSI Ps... 06/13". I break it down in the follow table:

Parts	full name	ascii code (hex)	breakdown of example "\e[1;33m"
CSI	Control Sequence Introducer	For 8-bit mode: 0x9b For 7-bit mode: 0x1b5b("\e[")	"\e[" is CSI
Ps…	parameters	each control function can have one or more parameters.	"1;33" are two parameters
		SGR can have multiple parameters. Each parameter is an integer represented in decimal notation.	1 means bold; and 33 means yellow foreground color
		Parameters are separated by 0x3b (';')
06/13	control function SGR	0x6d ('m')	"m"

You may wonder why parameter 33 means yellow and parameter 1 means bold. You cannot feed arbitrary parameter values to SGR. The allowed parameter values are (copied from [1]) shown below. The items marked as bold text are the commonly used parameters.

0 default rendition (implementation-defined), cancels the effect of any preceding occurrence of SGR in
the data stream regardless of the  setting of the GRAPHIC RENDITION COMBINATION MODE
(GRCM)
1  bold or increased intensity
2  faint, decreased intensity or second colour
3 italicized
4 singly underlined
5  slowly blinking (less then 150 per minute)
6  rapidly blinking (150 per minute or more)
7 negative image
8 concealed characters
9  crossed-out (characters still legible but marked as to be deleted)
10  primary (default) font
11  first alternative font
12  second alternative font
13  third alternative font
14  fourth alternative font
15  fifth alternative font
16  sixth alternative font
17  seventh alternative font
18  eighth alternative font
19  ninth alternative font
20 Fraktur (Gothic)
21 doubly underlined
22  normal colour or normal intensity (neither bold nor faint)
23  not italicized, not fraktur
24  not underlined (neither singly nor doubly)
25  steady (not blinking)
26  (reserved for proportional spacing as specified in CCITT Recommendation T.61)
27 positive image
28 revealed characters 
29  not crossed out
30 black display
31 red display
32 green display
33 yellow display
34 blue display
35 magenta display
36 cyan display
37 white display
38  (reserved for future standardization;  intended  for setting character foreground colour as specified in
ISO 8613-6 [CCITT Recommendation T.416])
39  default display colour (implementation-defined)
40 black background
41 red background
42 green background
43 yellow background
44 blue background
45 magenta background
46 cyan background
47 white background
48  (reserved for future standardization; intended for setting character background colour as specified in
ISO 8613-6 [CCITT Recommendation T.416])
49  default background colour (implementation-defined)
50  (reserved for cancelling the effect of the rendering aspect established by parameter value 26)
51 framed
52 encircled
53 overlined
54  not framed, not encircled
55 not overlined
56  (reserved for future standardization)
57  (reserved for future standardization)
58  (reserved for future standardization)
59  (reserved for future standardization)
60  ideogram underline or right side line 
61  ideogram double underline or double line on the right side 
62  ideogram overline or left side line
63  ideogram double overline or double line on the left side
64  ideogram stress marking
65  cancels the effect of the rendition aspects established by parameter values 60 to 64

More

PS1 is only one of the places where you can specify terminal control sequence. Many other programs also accept it. For example, in my .inputrc (config for readline), I have config like:

"\e[1~": beginning-of-line               # control sequence ending with '~' is for private use.
"\e[4~": end-of-line                        # In other words, we hope these control sequences are sent to terminal
                                                    # when we try to move cursor to the beginning/end of the line
                                                    # (e.g. press home/end key), and terminal can understand them

"\e[5C": forward-word                     # ECMA-48 section 8.3.20 CUF - cursor right
"\e[5D": backward-word                  # ECMA-48 section 8.3.18 CUB - cursor left
"\e[1;5C": forward-word                  # Other config is not specified in the standard.
"\e[1;5D": backward-word               # They may be extensions or just non standard compliant implementation
"\e\e[C": forward-word
"\e\e[D": backward-word
"\e[1;\e[C": forward-word
"\e[1;\e[D": backward-word

I added comments into the config so you can easily know the references.
If you are not sure what key sequence is sent when you press home/end key on your keyboard, run command "cat -v", and press the key. For me, cat shows "^[[1~" when I press home key. You can replace "^[" with "\e" and get the terminal control sequence.

References:

[1] http://www.ecma-international.org/publications/standards/Ecma-048.htm

Use bochs on Ubuntu

Install packages:

sudo apt-get install bochs
sudo apt-get install bochs-x
sudo apt-get install bochs-sdl
sudo apt-get install bochs-term

BIOS ROM image is installed by package bochsbios.
  -  /usr/share/bochs/BIOS-qemu-latest
  -  /usr/share/bochs/BIOS-bochs-legacy
  -  /usr/share/bochs/BIOS-bochs-latest
  -  …

/etc/bochs-init/bochsrc: is NOT loaded.

Multiple display libraries are supported (e.g. sdl, x, term). You can change it by setting "display_library".

if you use term as display library, to quit simulation, run command "kill -HUP <process_id>" in a separate console.

Create an empty floppy image: dd if=/dev/zero of=flooy-drive/floppy.img bs=512 count=1

Copy binary to the floppy image: dd if=<name>.bin of=floppy-drive/floppy.img

exclude directories when using GNU tar

tar zvcf name.tar.gz --exclude path/to/dir1 --exclude path/to/dir2 path/to/tar

Note:

1. Do not include a trailing '/' in the path of excluded directories.  Otherwise, it won't work.
2. Put --exclude before the directory/file to be tarred.

Install RPM packages with non-root account

Recently, I need to install RPM to RedHat Linux, but I don't have root access.  I found this post: http://ajaya.name/?p=6353.  However, some commands in the command are not correct or need more clarification.  So I wrote down my experience below.

• create file ~/.rpmmacros and add following line
      %_rpmlock_path lib/rpm/__db.000
• Initialize the database by running command:

rpm --initdb \

    --root /home/<user_name>/rpm-local/ \

    --dbpath /home/<user_name>/rpm-local/lib/rpm

• Check the dependence

rpm --root /home/<user_name>/rpm-local/ \
    --dbpath /home/<user_name>/rpm-local/lib/rpm \
    -ivh package.rpm

• Install package

rpm --root /home/<user_name>/rpm-local \
    --dbpath /home/<user_name>/rpm-local/lib/rpm \ 
    --relocate /usr=/home/<user_name>/rpm-local \
    --nodeps \
    -ivh package.rpm

Resources

• https://bugzilla.redhat.com/show_bug.cgi?id=222194
• http://www.redhat.com/archives/rpm-list/2007-May/msg00037.html
• https://rhn.redhat.com/errata/RHBA-2006-0440.html

How to get network information in Linux

Following files/dirs can be directly read:

/proc/net/dev
/sys/class/net/<if_name>/
/sys/class/net/<if_name>/statistics

Tool netstat is your friend to get network-related information:

netstat -I  # display interface info
netstat -s  # display statistics info
netstat -r  # display routing info
netstat -tlnp  # display TCP listening info

Other tools: sar, ifconfig, iftop

How to see network card and disk speed

Sometimes, you may want to know the hardware speed limit for network interface cards and disks.

Network Interface Card

I use commands

dmesg | grep -i ethernet
dmesg | grep -i infiniband

The output looks like

Intel(R) Gigabit Ethernet Network Driver - version 2.1.0-k2-1
igb 0000:0b:00.0: Intel(R) Gigabit Ethernet Network Connection
igb 0000:0b:00.1: Intel(R) Gigabit Ethernet Network Connection

and

mlx4_ib: Mellanox ConnectX InfiniBand driver v1.0 (April 4, 2008)
Registered RDS/infiniband transport

I also use command

/sbin/lspci

The output has following useful information

0b:00.0 Ethernet controller: Intel Corporation 82575EB Gigabit Network Connection (rev 02)
0b:00.1 Ethernet controller: Intel Corporation 82575EB Gigabit Network Connection (rev 02)
10:00.0 InfiniBand: Mellanox Technologies MT26418 [ConnectX VPI PCIe 2.0 5GT/s - IB DDR / 10GigE] (rev a0)

Disk

/sbin/lspci | grep -i ata

Other useful tools

mii-tools
hdparm

They need root privilege usually.

Extract some continuous lines from a file

Sometimes, I want to extract some continuous lines from a file, e.g. line 10 to line 100. I was thinking whether there is any linux command to do that. Unfortunately, I did not find the command in vanilla Linux distros. Suddenly, I found that it can achieved by combining commands head and tail.

Let's say you want to extract line min to line max, both inclusive.
Calculate nlines=(max-min+1). Then use following command:

cat <filename>|head -n <max>|tail -n <nlines>

Compile and Install vim on Linux

Commands

wget ftp://ftp.vim.org/pub/vim/unix/vim-7.3.tar.bz2
tar jvxf vim-7.3.tar.bz2
cd vim73
./configure --enable-gui=no \
            --enable-multibyte \
            --enable-cscope \
            --disable-netbeans \
            --prefix=<your_desired_vim_home>
make
make test
make install

Change you environment variable PATH to add vim bin path. Following commands are for bash.

Temporary change
    export PATH="<your_vim_home>/bin;$PATH"

Permanent change
    echo -e '\nexport PATH="<your_vim_home>/bin;$PATH" ' >> ~/.bash_profile

Delete executables and object (.o) files

Following two commands can delete all ELF executables and ELF object (.o) files.

find ./ -executable -type f|xargs -I{} file {} | grep ELF|cut -d ':' -f 1|xargs -I{} rm {}   

find ./ -name "*.o" -type f|xargs -I{} file {} | grep ELF|cut -d ':' -f 1|xargs -I{} rm {}

Some executables may not be found because its "x" bit is not set. Use following command to find them

find ./ -type f|xargs -I{} file {} | grep ELF|cut -d ':' -f 1|xargs -I{} rm {}

Note:
    -executable is not supported in old version of find.

How to change hostname in Ubuntu

Temporary change

    hostname <new_host_name>

Permanent change

1. Edit /etc/hostname to specify your new hostname
   sudoedit /etc/hostname
2. sudo service hostname start

Ubuntu init scripts and upstart jobs

Init script

Those scripts are located in directory /etc/init.d. Note: some of them have been converted to upstart jobs (see next section) and they should not be invoked directly.  To check whether it's a upstart job, check directory whether file /etc/init/<job>.conf exists for a specific job.

upstart jobs

http://upstart.ubuntu.com/  Use "man 5 init" to see the syntax of the conf file.

Each upstart job has a conf file in directory /etc/init/<job>.conf. You should not directly invoke the init script to start/stop the job. You should use commands initctl to do that. E.g. initctl restart hostname. 
initctl list will list upstart jobs that are running.

service

It can be used to interact with the init scripts, no matter they are upstart jobs or regular init script. For upstart jobs, it does not run /etc/init.d/<job> . Instead it runs "start <job>" directly.

E.g.   service hostname status

invoke-rc.d

Another tool to start/stop init jobs. In my opinion you should use command service because invoke-rc.d does NOT detect whether the job is a upstart job or regular init job. Usually, this is not a big deal because upstart job shell script automatically calls initctrl related commands (start, stop, reload, etc) .

Example - network

I will give an example about how network interfaces are managed by init daemon.

As you may know, ifup and ifdown can be used to bring up or down network interfaces.

/etc/network/interfaces are used by ifup and ifdown to know how you want your system to connect to the network.

Sample file

# interfaces lo and eth0 should be started when ifup -a is invoked.
auto lo eth0
# eth1 is allowed to be brought up by subsystem hotplug.
allow-hotplug eth1
# For interface lo, it should use internet protocol and it is a loopback device.
iface lo inet loopback
# Interface eth1 uses internet protocol and dhcp for configuration
iface eth1 inet dhcp

• For upstart job networking, its config file is /etc/init/networking.conf:

description "configure virtual network devices"

start on (local-filesystems
      and stopped udevtrigger)

task

pre-start exec mkdir -p /var/run/network

exec ifup -a

Notice the last line? Yes, it invoke ifup to bring up those interfaces that are marked as "auto" in file /etc/network/interfaces.

• Job network-interface is used when a network interface is added or removed. Its config file is /etc/init/network-interface.conf

description "configure network device"

start on net-device-added
stop on net-device-removed INTERFACE=$INTERFACE

instance $INTERFACE

pre-start script
    if [ "$INTERFACE" = lo ]; then
    # bring this up even if /etc/network/interfaces is broken
    ifconfig lo 127.0.0.1 up || true
    initctl emit -n net-device-up \
        IFACE=lo LOGICAL=lo ADDRFAM=inet METHOD=loopback || true
    fi
    mkdir -p /var/run/network
    exec ifup --allow auto $INTERFACE
end script

post-stop exec ifdown --allow auto $INTERFACE

Line "exec ifup --allow auto $INTERFACE" bring up the newly added interface if it is set to be brought up automatically.  The trigger event is "net-device-added" or "net-device-removed" which is sent by upstart-udev-bridge. It basically forwards events received from udev to init daemon. When your network interface (e.g. eth0) is detected by udev, finally a net-device-added event is sent to network-interface upstart job which runs ifup to bring it up.

• upstart job hostname. (/etc/init/hostname.conf). It includes following line:
    exec hostname -b -F /etc/hostname
  Now you should know how to change hostname.
  Edit file /etc/hostname, run command "sudo service start hostname", "sudo start hostname", or "sudo initctl start hostname".

Recover corrupted partition table

Partition table of my linux drive was corrupted recently.  I could not start up my Ubuntu.

I burned a Ubuntu CD. But when I tried to boot into the liveCD, it always gave me errors. It seems to be a CD burning/CD drive problem. Then I made a live USB drive which worked great. Following two tools can be used to "guess" the partition table.

• gpart
  This program is kind of old and is not maintained any longer. It can just recognizes some file systems (ext3, ext4, etc are not recognized correctly)
• testdisk
  This is a great tool which a text UI. You can find information here. You just follow the instructions. Check the "guessed" partition table match your real partition table(if you have backup, you are lucky.).

Run fsck to check integrity of your file system.

Afterthoughts:

1. Back up your partition table!
2. USB drive is more stable than CD in this case.

printf cheatsheet

Format string

  % [flag]* [minimum_field_width] [precision] [length_modifier] <conversion_specifier>

Flags

Flag	Description
#	The value should be converted to an "alternate form".
0	zero padded. By default, blank padded
-	left adjusted
' '	(A single space) A blank should be left before a positive number (or empty  string)  produced by a signed conversion.
+	A sign is always placed before a number produced by a signed conversion.

Minimum Field Width

"a decimal digit string (with  non-zero first digit). If the value has fewer characters, it will be padded.  In no case does a nonexistent or small field width cause truncation of a field."

Precision

a period ('.')  followed by an optional decimal digit string. It has different meanings for different conversions.

Precision	Description
d, i, o, u, x, and X	minimum number of digits to appear	printf("%.2d", 1) ==> "01"
a, A, e, E, f, and F	number of digits to appear after  the radix  character	printf("%.2f",0.1) ==> "0.10"
g and G	maximum number of significant digits
s and S	maximum number of characters to be printed from a string	printf("%.2s","hello") ==> "he"

Length Modifier

For each conversion specifier, there is expected argument type. For example, for conversion d,  and i, type of arguments should be int. Length Modifiers can be used to specify argument types rather than expected type by default.

Modifier	Conversion	Argument types
hh	d, i, o, u, x, or X	signed char or unsigned char
	n	signed char*
h	d, i, o, u, x, or X	short int or unsigned short int
	b	short int*
l	d, i, o, u, x, or X	long int, or unsigned long int
	n	long int*
	c	wint_t
	s	wchar_t
ll	d, i, o, u, x, or X	long long int, or unsigned long long int
	n	long long int*
L	a, A, e, E, f, F, g, or G	long double
j	d, i, o, u, x, or X	intmax_t, uintmax_t
z	d, i, o, u, x, or X	size_t, ssize_t
t	d, i, o, u, x, or X	ptrdiff_t

Conversion specifier

conversion	arguments	notation
d, i	int argument	signed decimal notation
o, u, x, X	unsigned int	unsigned octal, unsigned decimal, unsigned hexdec notation	abcedf are used for x. ABCDEF are used for X.
e, E	double	rounded and converted in the style [-]d.ddde±dd	precision is 6 by default.
f, F	double	rounded  and  converted  to  decimal  notation in the style [-]ddd.ddd	precision is 6 by default.
g, G	double	converted in style f or e (or F or E for G  conversions). Style e  is  used  if the  exponent from its conversion is less than -4 or greater than or equal to the precision.
a, A	double	converted to hexadecimal notation. for a, (using the letters abcdef) in the style [-]0xh.hhhhp±d;	C99;  not in SUSv2
c	int	converted to an unsigned char, and the resulting character is written
s	const char*	Characters from the array are written.
p	void *	printed in hexadecimal (as if by %#x or %#lx)
n	int *	The number of characters written so far is stored into the integer  indicated  by  the int * (or variant) pointer argument.

Some Hard Drive and File System benchmark tools

IOMeter

 

iozone

http://www.iozone.org

Document: http://www.iozone.org/docs/IOzone_msword_98.pdf
Manual: http://linux.die.net/man/1/iozone

Read, write, re-read, re-write, read backwards, read strided, fread, fwrite, random read/write, pread/pwrite variants

iozone -a | tee result.txt

iozone supports bunch of command line options. I summarized them in following table

Category	Options	Note
Auto mode	-a: record size 4k - 16M, file size 64k - 512M. -z: Used in conjunction with -a to test all possible record sizes. (Normally Iozone omits testing of small record sizes for very large files when used in full automatic mode. ) -A: more coverage
Test file	-f filename: the name for temporary file under test. -F fn1 fn2: # of files should be equal to # of processors/threads
Output	-b filename: output of an Excel compatible file -R: Generate Excel report.
Record size	-r #: record size -y #: minimum record size for auto mode -q #: maximum record size for auto mode
File size	-s #: size of the file to test -g #: maximum file size for auto mode -n #: minimum file size for auto mode
tests	-i #: specifies which test to run 0=write/rewrite, 1=read/re-read, 2=random-read/write, 3=Read-backwards, 4=Re-write-record, 5=stride-read, 6=fwrite/re-fwrite, 7=fread/Re-fread, 8=mixed workload, 9=pwrite/Re-pwrite, 10=pread/Re-pread, 11=pwritev/Re-pwritev, 12=preadv/Re-preadv	One will always need to specify 0 so that any of the following tests will have a file to measure. This means -I 0 creates files used by following tests. -i # -i # -i # is also supported so that one may select more than one test.
	-+p percent_reads: the percentage of threads/processes that will perform read testing in the mixed workload test case
	-+B: sequential mixed workload testing
throughput tests	-t #: Run Iozone in a throughput mode. -T: Use POSIX pthreads for throughput tests	This option allows the user to specify how many threads or processes to have active during the measurement.
processes/threads	-l #: lower limit on number of processes to run -u #: upper limit on number of processes to run
Timing	-c: include close() in timing calculation -e: include fflush(), fsync() in timing calculation
Other control	-H #: Use POSIX async I/O with # async operations -k #: Use POSIX async I/O (no bcopy) with # async operations. -I: use direct I/O if possible -m: use multiple buffers internally -o: Writes are synchronously written to disk -p: purges the processor cache before each file operation. -W Lock file when reading or writing. -K:  Inject some random accesses in the testing.

Examples

It's important to use -I option to turn on DIRECT I/O. Otherwise, linux's page caches (buffer cache) may give you ridiculous fast read speed.

• Auto Mode

• iozone -a -n 512m -g 1g
  
• 
  

• Single Test

• Sequential write, Sequential reads
  iozone -r 64k -s 1g -b excel.xls -R -i 0 -i 1 -I
• Use two processes to test sequential writes, sequential reads
  iozone -r 64k -s 1g -b excel.xls -R -i 0 -i 1 -I -l 2 -u 2
• Use one and two processes to tests (two runs. In first run, one process is created. In second run, two processes are created)
  iozone -r 64k -s 1g -b excel.xls -R -i 0 -i 1 -I -l 1 -u 2
• Random writes, Random reads
  iozone -r 64k -s 1g -b excel.xls-R -i 0 -i 1 -K -I

• Throughput Test

• iozone -t 2
  roughly equivalent to "iozone -l 2 -u 2"

• Mixed Workload Test

• iozone -r 64k -s 1g -b excel.xls -R -i 0 -i 8 -+p 50

Result visualization

./Generate_Graphs  result.txt

It will a directory for each operation (e.g. read, write, fread, fwrite). In each directory, there are two files generated - iozone_gen_out.gnuplot and <operation>.ps (this file is generated after you view the corresponding result using gnuplot).  Under the hood, it uses gnu3d.dem to render the data using Gnuplot after those data files are generated for all tested operations. You can call it directly without regenerating separate data files.

gnuplot gnu3d.dem

There are two more scripts that can be used for visualization - report.pl and iozone_visualization.pl.
When I tried to run them in Linux (using command ./report.pl result.txt), I had following error:

    -bash: ./iozone_visualizer.pl: /usr/bin/perl^M: bad interpreter: No such file or directory

You can use command perl report.pl result.txt to run it successfully.
The solution is to change those two files from dos type to unix type (mainly the new line character conversion).

sudo aptitude install tofrodos
fromdos report.pl
fromdos iozone_visualizer.pl

Now, you should be able to report.pl and iozone_visualization.pl directly. When they are run, a directory named 'report_result' is created. In the directory are Gnuplot scripts (*.do files) and PNG images for all tested operations. Those PNG images are generated by running those Gnuplot scripts. For example, read.png is generated by running "gnuplot read.do". A HTML page (index.html) is generated by iozone_visualization.pl which contains all of those PNG images in the same page.

Bonnie

http://www.textuality.com/bonnie/

• Bonnie64

  http://code.google.com/p/bonnie-64

• Bonnie++

  After you download the source, just execute following commands to build and run.
    ./configure --prefix=installation_dir
    ./make
    ./make install
    cd <installation_dir>/sbin/
    ./bonnie++

• http://www.coker.com.au/bonnie++/
  Manual: http://linux.die.net/man/8/bonnie++

Resources

• http://fsbench.filesystems.org/
• http://www.benchmarkhq.ru/english.html?/be_hdd.html

awk/gawk notes

RS	Record Separator	single character	That character separates the records.
		regular expression	Text in input matches reg exp separates records.
		null string	Records are separated by blank lines. The  newline character always acts as a field separator, in addition to whatever value FS may have.
NR	number of records seen so far
FNR	The input record number in the current input file
ORS	output record separator
FS	Field separator	single character	Fields are separated by that character
		single space	fields are separated by runs of spaces  and/or  tabs  and/or  newlines.
		Null string	each individual character becomes a separate field.
		regular expression
OFS	output field separator
FIELDWIDTHS		a space separated list of numbers	each field is expected to have fixed width. The value  of  FS  is ignored.  Assigning a new value to FS overrides the use of FIELDWIDTHS, and restores the default behavior.
NF	number of fields		Decrementing NF causes the values of fields past the new value to be lost, and the value of $0 to be recomputed
IGNORECASE	Controls the case-sensitivity of all regular expression  and  string  operations.	non-zero zero	non-zero: ignore case
Field Reference	How to reference a field	$1, $2, … $NF	Access a field. Assigning  a value to an existing field causes the whole record to be rebuilt when $0 is referenced.
		$-1, $-2	fatal error
		non-existent fields	For read, produce null-string. For write, 1)increase NF 2) create intervening fields with null string 3) $0 is recomputed
		$0	whole record.  assigning a value to $0 causes the record to be  resplit,  creating  new values for the fields.
CONVFMT			A number is converted to a string by using the value  of  CONVFMT  as  a  format  string  for  sprintf(3), with the numeric value of the variable as the argument.  However, even though all numbers in AWK are floating-point, integral values are always converted as  integers.
OFMT

All arrays in AWK are associative, i.e. indexed by string values.

i = "A"; j = "B"; k = "C"
x[i, j, k] = "hello, world\n"

key is "A\034B\034C" and value is "hello, world\n". Key test: val in array. for(val in array)…

Deb package manipulation notes (deb make, view, install, etc)

Directory /var/lib/dpkg/info/ contains package related files. For each package, its conffiles, md5sums, preinst, postinst, prerm, postrm, list of installed files, etc are kept there.

dpkg-dev

debian/files: "The  list  of  generated files which are part of the upload being prepared."

.changes: upload control file

dpkg-buildpackage
build binary or source packages from sources

dpkg-architecture: set and determine the architecture for package building

dpkg-checkbuilddeps: check build dependencies and conflicts. By default, debian/control is read.

dpkg-distaddfile: adds an entry for a named file to debian/files.
dpkg-genchanges:
dpkg-gencontrol:  generate Debian control files
dpkg-gensymbols:

dpkg-name
dpkg-scanpackages: create Packages index files
dpkg-scansources: create Sources index files
dpkg-shlibdeps
dpkg-source: packs and unpacks Debian source archives.
dpkg-vendor: query vendor information
dpkg-parsechangelog: get changelog information

Vendor

/etc/dpkg/origins/default

devscripts

debchange

debhelper

dh-make

This package is useful when you have a regular source package (not debian source package) and want to debianlize it.
dh_make must be invoked within a directory containing the source code, which must be named <packagename>-<version>. The <packagename> must  be  all lowercase, digits and dashes.
As I mentioned, there are two types of debian source packages – native and non-native.
For non-native package, obviously you need the original source tree. The reason is that the original source tree is needed to deb tools to generate diff. dh_make makes sure original source tarball(<packagename>_<version>.orig.tar.gz) exists.
Option –f can be used to specify location of the tarball.
If –f is not given, dh_make searches parent directory for file <packagename>_<version>.orig.tar.gz and directory <packagename>_<version>.orig. If either of them exists, it will be fine. If neither exists, dh_make will complain and exit.
If you want to create a original source tarball based on the code in current directory, use option "—createorig". Then current directory is copied to <packagename>_<version>.orig in parent directory.

key: public key
secret: private key

Trusted pub keys are stored in file /etc/apt/trusted.gpg (not /etc/apt/trustdb.gpg)

apt-key list

gpg --recv-keys --keyserver keyserver.ubuntu.com key_ID_here;
gpg --export --armor key_ID_here | sudo apt-key add -

http://wiki.debian.org/SecureApt
https://help.ubuntu.com/community/SecureApt

Downloaded deb packages are stored at /var/cache/apt/archives/ and /var/cache/apt/archives/partial/.

Low-level understanding

Deb binary package format

man deb
The manual describes debian binary package format
deb package is ar archive. So you can read content of a deb package using command:
    ar tf pkg_name.deb
On my machine, the output is

    debian-binary 
    control.tar.gz 
    data.tar.gz 

Extract content of a deb pkg using command:
  ar xof pkg_name.deb

Deb control

control.tar.gz is a control file. Its format is deb-control.
"It is a gzipped tar  archive  containing the  package  control  information,  as a series of plain files, of which the file control is mandatory and contains the core control information."
Use command tar zvxf control.tar.gz to extract control files. The most important file is control. The format of the file is described in man deb-control.
conffiles: this file lists all configuration files used by this package.
control:
md5sums 
postinst
postrm  
preinst 
prerm

Deb data

"It contains the filesystem as a tar archive, either not compressed".

High-level understanding

Ubuntu provides some tools to make it more convenient to manipulate deb package so that users don't need to use ar, tar, etc to extract files/information manually.

First, command dpkg-deb comes really handy

    dpkg-deb –I: provides information of a deb pkg. (Extracts info from file control) 
    dpkg-deb –c: list content of the package. (Extracts info from data.tar.gz)
    dpkg-deb –x: extract a deb archive 
    dpkg-deb –X: extract a deb archive and print list of extracted files. 
    dpkg-deb –e: extract control information to DEBIAN directory if not specified.
                 (Extract files from control.tar.gz)

Deb Source Package

Format of source package is described in section "SOURCE PACKAGE FORMATS" within manual "man dpkg-source".
Also read http://www.debian.org/doc/debian-policy/ch-source.html for more info.

There are two types of source packages: native and non-native.
Layout of native package

  .dsc: includes package info and md5 checksum for the package content.
  .tar.gz

Layout of non-native package:

  .dsc: debian source control 
  .orig.tar.gz: source code
  .diff.gz: 1)patches applied to the source code; 2) debian package (debain/ dir)

Download a source package instead of binary packge:

  apt-get source pkg_name     #Download and unpack
  apt-get source --download-only pkg_name    #only download

Then command dpkg-source comes handy to manipulate source package.

  dpkg-source –x pkg_name.dsc    # Extract a source package. 

If you use command "apt-get source pkg_name", the package has been download and extracted. So you don't need to execute this command. If you use command "apt-get source --download pkg_name", you can use this command to extract the downloaded package and apply the patch.
If you don't want the patch to be applied, add option --skip-debianization.

If the directory where you execute command "dpkg-source –x" is different from the directory where downloaded source package is stored, option "-su, –sp, sn" can be used to specify where source tarball will be copied to current direcotory.

In all cases any existing original source tree will be removed! So be sure to backup your code if it is in current directory.

  dpkg-source –sn –x pkg_name.src    #original source tarball is not copied to current directory. But source tree is unpacked to current dir and patch is applied
  dpkg-source –sp –x pkg_name.src    #source tarball is copied to current directory, unpacked, and patch is applied
  dpkg-source –su –x pkg_name.src    #Copy source tarball to current directory, both original source tree and patched source tree are extracted.

If you want the original source is extracted also, use command "dpkg-source –su –x pkg_name.dsc".
When I extracted the source package, I got following warning:
gpgv: Can't check signature: public key not found
dpkg-source: warning: failed to verify signature on ./pkg_name.dsc

This means public key has not been found which is needed to verify signature of the package. The dpkg-source manaul can tell you more:

--no-check
  Do not check signatures and checksums before unpacking.
--require-valid-signature
  Refuse to unpack  the source package if it doesn't contain an OpenPGP signature that can be verified either with the user's trustedkeys.gpg keyring, one of the vendor-specific  keyrings,  or  one of the official Debian keyrings (/usr/share/keyrings/debiankeyring.gpg and /usr/share/keyrings/debianmaintainers.gpg).

debian/ direcotory

Version:
https://wiki.ubuntu.com/PackagingGuide/Complete#changelog

changelog

Default file is located at debian/changelog. Changelog contains a list of changes. Note: it has a specific format. Command debchange can be used to edit the file.

debchange –a        #append a changelog entry at current version
debchange –i         #increase release number for non-native packages (2.4-1ubuntu1 –> 2.4-1ubuntu2).
debchange –v        #create a changelog entry for a arbitrary new version.
debchange --create  #create a new changelog file
debchange –c changelogfile  #edit a specified changelog file instead of default one.

Read http://www.debian.org/doc/debian-policy/ch-source.html#s-dpkgchangelog for more info.

dpkg-source –b   # build source package
man deb-version
Debian package version number format

Export:
gpg --export-secret-keys keyID
gpg --export keyID    #export public key
gpg --gen-key
gpg –k   #list pub keys
gpg –K   #list secret keys

copyright

Read this: https://wiki.ubuntu.com/PackagingGuide/Basic#Copyright%20Information

control

https://wiki.ubuntu.com/PackagingGuide/Complete#control

rules
It specifies how to compile, install the app and create the .deb package.
https://wiki.ubuntu.com/PackagingGuide/Complete#rules

DEBFULLNAME:
DEBEMAIL:

Package build

Binary package

dpkg-buildpackage
debuild: wrap dpkg-buildpackage and some other tools. Or you can set variable DEBSIGN_KEYID to the key id.
Use debuild –kKEYID to specify the key used to sign the package.
If you want to pass parameters to dpkg-buildpackage, set variable DEBUILD_DPKG_BUILDPACKAGE_OPTS.

debsign –kkeyID
debsign –m'LastName FirstName (Comment) <email_address>'

Source package: debuild –S

 

lintian
Debian package checker
  lintian -Ivai *.dsc

sudo pbuilder build pkg_name.dsc

dpkg-query –s pkg_name    #conf files are listed

https://wiki.ubuntu.com/PackagingGuide/Complete
https://wiki.ubuntu.com/DebootstrapChroot
https://wiki.ubuntu.com/PackagingGuide/Basic
https://wiki.ubuntu.com/PbuilderHowto
https://help.ubuntu.com/community/GnuPrivacyGuardHowto

http://www.debian.org/doc/FAQ/ch-pkg_basics.en.html

http://www.debian.org/doc/manuals/maint-guide/index.en.html

http://www.debian.org/doc/debian-policy/

Install a package from Debian repository for Ubuntu

You can directly use Debian repository. But Debian packages may or may not be compatible with Ubuntu. So you take your own risks by doing so. Another way is to download source and build the package, which is described below.

1) Add a line to /etc/apt/sources.list

    deb-src repo-url

2) Update package index

    sudo apt-get update

3) Install dependencies: (These dependencies are downloaded from Ubuntu repository, not Debian repository)

    sudo apt-get build-dep pkg_name

4) Download source and build package

    apt-get -b source pkg_name

Now you should have a pkg_name.deb file generated in current directory.

5) Install the package

    sudo dpkg -I pkg_name.deb

6) Revert /etc/apt/sources.list file by removing the line added in step 1).

7) Rebuild package index

    sudo apt-get update

 

You are done!

Arrays in Bash (Cheatsheet)

Description	Indexed array	Associative array
Declare an array	declare -a array	declare -A array
Assignment	array=(value1 value2 … valuen)	array=([sub1]=value1 … [subN]=valueN) Note:You must declare it first you can use declare -A array=([sub1]=value1 … [subN]=valueN)
Expand to all values	${array[@]}  or ${array[*]}	${array[@]}  or ${array[*]}
Expand to all keys	${!array[@]}  or ${!array[*]}	${!array[@]}  or ${!array[*]}
length of an array	${#array[@]} or ${#array[*]}	${#array[@]} or ${#array[*]}
Remove entire array	unset array or unset array[@] or unset array[*]	unset array or unset array[@] or unset array[*]
Remove an element	unset array[index]	unset array[index]
Array join	array1+=(${array2[@]}) or array1+=(v1 v2 … vN)	array1+=([sub1]=v1 [sub2]=v2 … [subN]=vN)
Length of an element:	${#array[index]}	${#array[index]}

 

Resources

http://tldp.org/LDP/abs/html/arrays.html

Bash config file loading order

interactive	login	files sourced	Related option
Y	Y	/etc/profile, {~/.bash_profile| ~/.bash_login| ~/.profile } Only one of the files in brackets will be executed.	--noprofile
N	Y
Y	N	/etc/bash.bashrc, ~/.bashrc	--norc

GNOME notes

GDM

/etc/init.d/gdm, /etc/init/gdm.conf: these two files are used to start gdm (actually gdm-binary).

Default display manager is stored here: /etc/X11/default-display-manager

GDM configuration: http://library.gnome.org/admin/gdm/2.32/gdm.html#configuration

Tools: gdmsetup

/etc/gdm

/user/share/gdm/

After the user logins in, gnome-session is invoked.

http://library.gnome.org/admin/system-admin-guide/stable/sessions-1.html.en

man gnome-session

Default session is specified at /desktop/gnome/session/default_session.

Use gconf-editor to view value of /desktop/gnome/session/default_session. In my case the value is "gnome-settings-daemon".
/usr/lib/gnome-settings-daemon/gnome-settings-daemon --gconf-prefix=/apps/gdm/simple-greeter/settings-manager-plugins. The description of option "--gconf-prefix" is "GConf prefix from which to load plugin settings"

 

Some resources:

http://live.gnome.org/SessionManagement/GnomeSession

http://standards.freedesktop.org/desktop-entry-spec/latest/

Autostart-spec:  http://standards.freedesktop.org/autostart-spec/autostart-spec-latest.html

http://lists.freedesktop.org/archives/xdg/2007-January/007436.html

Autostart apps are specified in directory /etc/xdg/autostart/, ~/.config/autostart/

 

Use /usr/bin/gnome-session-properties to set session properties (e.g. autostart programs). Those changes are specific to a user.