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Fluxbox

2010-03-31T18:44:58+02:00

Launch fluxbox at X init

localhost ~ # echo "exec startfluxbox" > ~/.xinitrc

FS

2010-05-11T12:06:28+02:00

Secure deletion

Encrypt the hard disk using a random key:

# cryptsetup create random_sdx /dev/sdx -d /dev/urandom

The fastest way with encryption (writes zeroes to the encrypted container, with a good cipher this results in random data on the physical disk):

# dd if=/dev/zero of=/dev/mapper/random_sdx bs=1M

Don't forget to clean up afterwards:

# cryptsetup remove random_sdx

Loop devices

List devices

srv-mvl mng-mvl # losetup -a
/dev/loop/0: [fd00]:8019972 (/var/xen/fw-mvl/fw-mvl.swap)
/dev/loop/1: [fd00]:7438528 (/var/xen/fw-mvl/fw-mvl.img)
/dev/loop/10: [fd00]:8019996 (/var/xen/gate-mvl/gate-mvl.img)
/dev/loop/11: [fd00]:8019995 (/var/xen/gate-mvl/gate-mvl.swap)
/dev/loop/14: [fd00]:9134082 (/var/xen/ex-mvl/ex-mvl.img)
/dev/loop/15: [fd00]:9134084 (/var/xen/ex-mvl/ex-mvl.swap)

Creation

create file

localhost ~ # dd if=/dev/zero of=ex-gif/ex-gif.img bs=1M count=2000
2000+0 records in
2000+0 records out
2097152000 bytes (2.1 GB) copied, 27.7524 s, 75.6 MB/s

make fs :

localhost ~ # mke2fs -j ex-gif/ex-gif.img

mount file base filesystem :

localhost ~ # mount -o loop ex-gif/ex-gif.img /mnt/gentoo

Increase disk image

this will add 500M to def-gentoo.img

localhost ~ # dd if=/dev/zero bs=1M count=500 >> def-gentoo.img
localhost ~ # e2fsck -f def-gentoo.img
localhost ~ # resize2fs def-gentoo.img

Crypt partition

localhost ~ # cryptsetup -y --cipher aes-cbc-essiv:sha256  --key-size 256 luksFormat /dev/sda4

open crypted :

localhost ~ # cryptsetup luksOpen /dev/sda1 myname

mount opened:

localhost ~ # mount /dev/mapper/myname /mnt/gentoo

close opened :

localhost ~ # umount /mnt/gentoo
localhost ~ # cryptsetup luksClose myname

dump for an encrypted fs :

localhost ~ # hexdump -n 256 -C /dev/sda1
00000000  4c 55 4b 53 ba be 00 01  61 65 73 00 00 00 00 00  |LUKS....aes.....|

Umount a device when busy

if you have that on unmounting a device :

localhost ~ # umount /media/disk/
umount: /media/disk: device is busy
umount: /media/disk: device is busy

use fuser to see which process use the device :

localhost ~ # fuser -m /dev/mapper/tst
tst:  5257c 20459c 20693c

see the process :

localhost ~ # ps auxw | grep 5257
root      5257  0.0  0.0  66212  1736 pts/0    Ss+  Aug07   0:00 -bash

and then kill the process :)

localhost ~ # kill 5257
localhost ~ # kill -9 5257

Inodes

Check inodes

localhost ~ # df -i
Filesystem            Inodes   IUsed   IFree IUse% Mounted on
/dev/mapper/md2      9838592  213992 9624600    3% /
udev                  436724    1759  434965    1% /dev
shm                   436724       1  436723    1% /dev/shm
/dev/loop0            192000  192000       0  100% /mnt/gentoo

Here you can see that /mnt/gentoo nodes is full, so you can not create new files anymore.

Set inodes on format

format with a specific number of inodes :

localhost ~ # mke2fs -j -N 300000 /dev/sdX

Convert ext2 to ext3

# tune2fs -j /dev/hda5

Label

Add label to partition :

# e2label /dev/mapper/sdi1 BACKUP

mount label partition :

# mount LABEL=BACKUP /mnt/backup

/etc/fstab

...
LABEL=BACKUP       /mnt/backup        ext4        noatime        0 1
...

How-to...

2010-03-31T18:46:48+02:00

Update user alias

File: /etc/mail/aliases

root:               root@example.org

and then run :

localhost ~ # newaliases

Show directory size

localhost ~ # du -sh
65G     .

localhost ~ # du -sh *
756K    cache
24M     db
4.0K    empty
65G     lib
8.0K    lock
5.4M    log
0       mail
68K     run

Find

Find program location

localhost ~ # whereis sendmail

Find string in files recursivly with showing also lines around

localhost ~ # grep -R -n1 "/usr/lib/sendmail" /etc
/etc/nail.rc-63-
/etc/nail.rc:64:# Use the local sendmail (/usr/lib/sendmail) binary by default.
/etc/nail.rc-65-# (Uncomment the following line to use a SMTP server)

Show system control values

localhost ~ # sysctl -a

Change a sysctl value (TCP keepalive values for exemple)

as root :

localhost ~ # sysctl -w net.ipv4.tcp_keepalive_time=15
localhost ~ # sysctl -w net.ipv4.tcp_keepalive_probes=2
localhost ~ # sysctl -w net.ipv4.tcp_keepalive_intvl=10

to persist, edit /etc/sysctl.conf and reload file :

localhost ~ # sudo sysctl -p /etc/sysctl.conf

dump file or block device content

dump for an encrypted fs :

localhost ~ # hexdump -n 256 -C /dev/sda1
00000000  4c 55 4b 53 ba be 00 01  61 65 73 00 00 00 00 00  |LUKS....aes.....|

Auto rebuild raid devices with mdadm after reboot on liveCD

localhost ~ # mdadm --auto-detect
localhost ~ # cat /proc/mdstat

Show connected client to a tcp port

localhost ~ # netstat -apn | grep :4445
tcp        0      0 10.40.0.32:34251            10.40.0.33:4445             ESTABLISHED 31798/java
tcp        0      0 10.40.0.32:34252            10.40.0.33:4445             ESTABLISHED 31885/java
tcp        0      0 10.40.0.32:34253            10.40.0.33:4445             ESTABLISHED 31966/java
tcp        0      0 10.40.0.32:34260            10.40.0.33:4445             ESTABLISHED 32044/java

Create an Xvnc server without security

# Xvnc -alwaysshared -localhost -desktop MyName -geometry 4000x3000 -once securitytypes=none :2 &

Mdadm

2009-12-30T23:45:18+02:00

stop raid device

# mdadm -S /dev/md2

when a raid 5 or 6 fail you have to rebuild using latest version of data :

get events of drives

# mdadm --examine /dev/sd[abcgf]2 | grep Event
         Events : 11369
         Events : 11369
         Events : 11369
         Events : 34
         Events : 34

force rebuild raid without the 2 latest drives

# mdadm -Af /dev/md2 /dev/sda2 /dev/sdb2 /dev/sdc2

then add back 2 bad drives

# mdadm -a /dev/md2 /dev/sdg2 /dev/sdf2

watch rebuild

# watch -n1 "cat /proc/mdstat"
...

Screen

2009-12-29T14:47:30+02:00



Shortcut	Command	Description

C-a '	select	Prompt for a window name or number to switch to.
C-a ”	windowlist -b	Present a list of all windows for selection.
C-a 0 .. 9	select 0 .. 9	Switch to window number 0 … 9
C-a -	select -	Switch to the blank window.
C-a [TAB]	focus	Switch the input focus to the next region.
C-a C-a	other	Toggle to the window displayed previously.
C-a a	meta	Send the command character (C-a) to window.
C-a A	title	Allow the user to enter a name for the current window.
C-a b	break	Send a break to window.
C-a C-b	“ “	“ “
C-a B	pow_break	Reopen the terminal line and send a break.
C-a c	screen	Create a new window with a shell and switch to that window.
C-a C-c	“ “	“ “
C-a C	clear	Clear the screen.
C-a d	detach	Detach screen from this terminal.
C-a C-d	“ “	“ “
C-a D D	pow_detach	Detach and logout.
C-a f	flow	Toggle flow on, off or auto.
C-a C-f	“ “	“ “
C-a F	fit	Resize the window to the current region size.
C-a C-g	vbell	Toggles screen's visual bell mode.
C-a h	hardcopy	Write a hardcopy of the current window to the file “hardcopy.n”.
C-a H	log	Begins/ends logging of the current window to the file “screenlog.n”.
C-a i	info	Show info about this window.
C-a C-i	“ “	“ “
C-a k	kill	Destroy current window.
C-a C-k	“ “	“ “
C-a l	redisplay	Fully refresh current window.
C-a C-l	“ “	“ “
C-a L	login	Toggle this windows login slot.
		Available only if screen is configured
		to update the utmp database.
C-a m	lastmsg	Repeat the last message displayed in
C-a C-m		the message line.
C-a M	monitor	Toggles monitoring of the current win.
C-a [space]	next	Switch to the next window.
C-a n
C-a C-n
C-a N	number	Show the number (and title) of the
		current window.
C-a [backsp]	prev	Switch to the previous window
C-a h		opposite of C-a n.
C-a p
C-a C-p
C-a q	xon	Send a control-q to the current win.
C-a C-q

C-a Q	only	Delete all regions but the current one.
C-a r	wrap	Toggle the current window's line-wrap
C-a C-r		setting (turn the current window's
		automatic margins on and off).
C-a s	xoff	Send a control-s to the current window.
C-a C-s
C-a S	split	Split the current region into two new
		ones.
C-a t	time	Show system information.
C-a C-t
C-a v	version	Display the version and compilation
		date.
C-a C-v	digraph	Enter digraph.
C-a w	windows	Show a list of window.
C-a C-w
C-a W	width	Toggle 80/132 columns.
C-a x	lockscreen	Lock this terminal.
C-a C-x
C-a X	remove	Kill the current region.
C-a z	suspend	Suspend screen. Your system must
C-a C-z		support BSD-style job-control.
C-a Z	reset	Reset the virtual terminal to its
		“power-on” values.
C-a .	dumptermcap	Write out a ”.termcap” file.
C-a ?	help	Show key bindings.
C-a C-\	quit	Kill all windows and terminate screen.
C-a :	colon	Enter command line mode.
C-a [	copy	Enter copy/scrollback mode.
C-a C-[
C-a [ESC]
C-a ]	paste .	Write the contents of the paste buffer
		to the stdin queue of the current win.
C-a {	history	Copy and paste a previous (command)
C-a }		line.
C-a >	writebuf	Write paste buffer to a file.
C-a <	readbuf	Reads the screen-exchange file into
		the paste buffer.
C-a =	removebuf	Removes the file used by C-a < and
		C-a >
C-a ,	license	Shows where screen comes from, where
		it went to and why you can use it.
C-a _	silence	Start/stop monitoring the current
		window for inactivity.
C-a *	displays	Show a listing of all currently
		attached displays.

TcpDump

2010-03-31T18:47:44+02:00

capture TCP paquet

Capturing packets based on network interface, ports and protocols.

localhost ~ # tcpdump -w test.pcap -i eth1 tcp port 8080

capture on destination ip

localhost ~ # tcpdump -w test.pcap dst 10.40.0.32 and tcp port 80

capture with 2 different ports

localhost ~ # tcpdump -w test.pcap -i eth1 tcp port 8080 or udp \( 33450 or 33451 \)

read tcp packet

localhost ~ # tcpdump -nnr test.pcap

formatting date

localhost ~ # tcpdump -ttttnnr test.pcap

capture full packet

localhost ~ # tcpdump -s 0 -ttttnnr test.pcap