Kenneth: /* mkfs */

2014-08-18T14:45:27Z

mkfs

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== A ==

=== alias ===

alias: manage command aliases

To list aliases:
alias
alias [ALIAS]
alias -p [ALIAS]

To create alias:
alias [ALIAS]="[COMMAND]"

To remove alias:
unalias [ALIAS]

CentOS 5 Examples:
<pre>
alias cp='cp -i'
alias l.='ls -d .* --color=tty'
alias ll='ls -l --color=tty'
alias ls='ls --color=tty'
alias mv='mv -i'
alias rm='rm -i'
alias which='alias | /usr/bin/which --tty-only --read-alias --show-dot --show-tilde'
</pre>

alias ls='ls -CF --color=tty'

To pass a parameter to alias, use a function instead: [http://www.cyberciti.biz/faq/linux-unix-pass-argument-to-alias-command/]
function foo() { /path/to/command "$@" ;}

== B ==

=== badblock ===

badblocks - search a device for bad blocks

Non Destructive read test:
badblocks -s /dev/sdb
# -s show

Destructive write test:
badblocks -s -w -t 0xff /dev/sdb
# -s show, -w write, -t test pattern

=== bc ===

bc - An arbitrary precision calculator language

Note: Default scale is 0, which means no decimal

<pre>
echo "scale=2 ; 1/2" | bc
echo '(1 + sqrt(5))/2' | bc -l
echo 'pad=20; min=64; (100*10^6)/((pad+min)*8)' | bc # This shows max FastE packet rate:
echo 'obase=16; ibase=10; 64206' | bc # Base conversion (decimal to hexadecimal)
seq 100 | (tr '\n' +; echo 0) | bc # Add a column of numbers.
echo 'ibase=16; 2DEC' | bc # Base conversion (hexadecimal to default decimal)
echo 'obase=16; ibase=10; 64206' | bc # Base conversion (decimal to hexadecimal)
echo 'obase=10; ibase=16; 2DEC' | bc # Base conversion (hex to dec)
</pre>

Or just use python!
echo "print 10 / 2.0" | python

== C ==

=== cut ===

cut - remove sections from each line of files

echo "one,two,three" | cut -f 1 -d "," # one
echo "one,two,three" | cut -b 1-2 # on
echo "one,two,three" | rev | cut -d , -f 1 | rev # three (last field)

other cool alternatives: [http://stackoverflow.com/questions/4563060/how-to-cut-the-last-field-from-a-shell-string]

echo "one two three" | awk '{print $NF}' # three (last field)
echo "one,two,three" | awk -F, '{print $NF}' # three (last field)
echo "/string/to/cut.txt" | awk -F'/' '{for (i=1; i<NF; i++) printf("%s/", $i)}'
awk -F, '{print $NF}' file

echo $LINE | grep -o '.*/'

basename /dev/sdb # sdb
dirname /dev/sdb # /dev

== D ==

=== dmesg ===

dmesg - print or control the kernel ring buffer

Display kernel ring:
dmesg

Clear kernel ring:
dmesg -c

Initial kernel ring at boot is saved to:
/var/log/dmesg

Kernel ring is also logged to:
/var/log/messages

=== du ===

du - estimate file space usage
:Summarize disk usage of each FILE, recursively for directories.

du --si
du -B M
du --max-depth=1
du -c dir1 dir2 # combined total

---

Find large files

Print largest files and size in bytes
find . -xdev -printf '%s %p\n' |sort -nr | head -20

find out top 10 largest file/directories is taking up the most space in a /var directory/file system:
du -a /var | sort -n -r | head -n 10

more human readable output try:
du -ks /var | sort -n -r | head -n 10

References:
* Linux Find Large Files - http://www.cyberciti.biz/faq/find-large-files-linux/
* How do I find the largest top 10 files and directories on a Linux / UNIX / BSD filesystem? - http://www.cyberciti.biz/faq/how-do-i-find-the-largest-filesdirectories-on-a-linuxunixbsd-filesystem/

== E ==

== F ==

== G ==

== H ==

== I ==

== J ==

== K ==

== L ==

=== less ===

less - opposite of more

cat /etc/passwd | less

Case insensitivity
less -i [FILE] # --ignore-case

Case sensitivity can be toggled within the program by typing "-i". [http://www.linux-mag.com/id/4442]

=== ln ===

ln - make links between files

Symbolic link:
ln -s [TARGET] [ [LINK] ]

Hard link:
ln [TARGET] [ [LINK] ]

Dereference links:
readlink [link] # best option
ls -l [link] | awk '{print $11}' # ok option
file [link] | awk '{print $5} # includes some ugly quotes

To find all hard links to a file:
find [BASEPATH] -xdev -samefile [LINK]

=== logger ===

logger - a shell command interface to the syslog(3) system log module

Log message to syslog

logger "message"

logger -t DNS-Made-Easy -s "Problem updating DNS record."

logger -t mail.info test

== M ==

=== mkinitrd ===

mkinitrd - is a compat wrapper, which calls dracut to generate an initramfs

mkinitrd [image] [kernel-version]
-f # overwrite if image exists
-v # verbose

=== mkfs ===

==== mkfs.vfat ====

Install:
yum install dosfstools

vfat:
mkfs -t vfat /dev/sdg1

fdisk /dev/sdb # n p 1 enter enter t 1 c w (part type: 0b or 0c)
mkfs.vfat -F 32 /dev/sdb1 # or mkfs.msdos
mkfs.vfat -F 32 /dev/sdb1 -n MOVIES # or mkfs.msdos

partition type:
b W95 FAT32 # BIOS INT 13 - Partitions up to 2047GB
c W95 FAT32 (LBA) # Extended-INT13 equivalent of 0b

"0x0b (FAT32 without LBA) uses the old BIOS INT 13 which means it can address a maximum of 7.8GB disk space" [http://www.linuxquestions.org/questions/linux-general-1/fdisk-created-fat32-partition-which-type-0b-or-0c-643261/]

=== modinfo ===

modinfo - program to show information about a Linux Kernel module

$ modinfo skge
filename: /lib/modules/2.6.18-92.1.18.el5/kernel/drivers/net/skge.ko
version: 1.6
license: GPL

=== mount ===

mount /dev/sdb1 /mnt

== N ==

=== nice ===

Nice and ReNice

-20 high priority
+19 low priority

A high nice value means a low priority for your process: you are going to be nice. A low or negative value means high priority: you are not very nice. The range of allowable niceness values is -20 to +19.

'''renice''' [http://www.linux-tutorial.info/modules.php?name=ManPage&sec=8&page=renice]
:Renice alters the scheduling priority of one or more running processes.

# change the priority of process ID's 987 and 32, and all processes owned by users daemon and root.
renice +1 987 -u daemon root -p 32

$ nice -n 5 ~/bin/longtask # Lowers priority (raise nice) by 5
$ sudo renice -5 8829 # Sets nice value to -5
$ sudo renice 5 -u boggs # Sets nice value of boggs's procs to 5

References:
* Major Tom, This is Job Control: Acting Nice with the Linux System - http://www.linuxplanet.com/linuxplanet/tutorials/2116/1/
* Linux Process Control - http://www.comptechdoc.org/os/linux/usersguide/linux_ugprocesses.html
* Linux.com :: Influence scheduling priority with nice and renice - http://www.linux.com/archive/feed/58638

=== nohup ===

nohup - run a command immune to hangups, with output to a non-tty

nohup [APPLICATION] &

Make sure to add the '&' to put the process into the background [http://www.cyberciti.biz/tips/nohup-execute-commands-after-you-exit-from-a-shell-prompt.html], or you will have to do it manually with:
[ctrl]+z
jobs
bg %1

To nohup a running process: [http://stackoverflow.com/questions/625409/how-do-i-put-an-already-running-process-under-nohup]
[ctrl]+z
jobs
bg %1
disown %1

== O ==

== P ==

=== parted ===

GNU Parted - a partition manipulation program

Used by OpenELEC to create SD card partitions: (create_sdcard)
<pre>
DISK = /dev/sdh

# writing new disklabel on $DISK (removing all partitions)...
parted -s /dev/sdh mklabel msdos

# creating partitions on $DISK...
parted -s "$DISK" unit cyl mkpart primary fat32 -- 0 16
parted -s "$DISK" unit cyl mkpart primary ext2 -- 16 -2

# make partition active (bootable)
parted -s "$DISK" set 1 boot on

# tell kernel we have a new partition table
partprobe "$DISK"

# create filesystem
# creating filesystem on $PART1...
mkfs.vfat "$PART1" -I -n System
# creating filesystem on $PART2...
mkfs.ext4 "$PART2" -L Storage

# sync disk
sync
</pre>

=== printf ===

printf - format and print data

printf:
printf "%'.2f" var
printf "%'.2d" var
printf "Total Rs.%'.2f" var
printf "Total $.%'.2f" var
printf "%'.2f\n" $x

References:
* Unix / Linux: Bash Number Currency Formatting Thousands Grouping Separator - http://www.cyberciti.biz/faq/unix-linux-bash-number-formatting-in-with-thousand-separator/

== Q ==

== R ==

== S ==

=== scp ===

scp file user@host:/some/path/
scp user@host:/some/path/file /some/path
scp -P 22 file user@host:/some/path/
scp -i myidentity file user@host:/some/path/

=== smartctl ===

SMART Tools

[http://smartmontools.sourceforge.net/ Smartmon Tools]

Get Disk Information:
smartctl -a /dev/sda

Turn on SMART:
smartctl -s on -o on -S on /dev/hda
# -s on # Enable/disable SMART on device (on/off)
# -o on # Enable/disable automatic offline testing on device (on/off)
# -S on # Enable/disable Attribute autosave on device (on/off)

How long has this disk (system) been powered on in total:
smartctl -A /dev/sda | grep Power_On_Hours

smartctl -i /dev/hda
smartctl -H /dev/hda
smartctl -t short /dev/hda
smartctl -l selftest /dev/hda

References:
*[http://www.linuxjournal.com/content/know-when-your-drives-are-failing-smartd Know when your drives are failing, with smartd | Linux Journal]

=== ssh ===

ssh user@host
ssh user@host some_command
ssh -p 22 user@host
scp -i myidentity user@host

---

Keep Alive:

# send keep alive every 30 seconds
ssh -o ServerAliveInterval=30 user@host

References:
*[http://madphilosopher.ca/2005/07/an-ssh-keep-alive-tip/ An ssh keep-alive tip]
*[http://ubuntu.wordpress.com/2006/02/03/keeping-ssh-sessions-alive/ Keeping SSH Sessions Alive ]
*[http://www.brandonhutchinson.com/OpenSSH_ClientAliveInterval.html OpenSSH ClientAliveInterval]
*[http://lists.maemo.org/pipermail//maemo-users/2007-May/005336.html Slow SSH connect to N800 (ServerAliveInterval)]
*[http://drupal.star.bnl.gov/STAR/comp/sofi/facility-access/ssh-stable-con/ SSH connection stability]

=== strace ===

strace - trace system calls and signals

List files opened by command:
strace -e trace=open vmkload_mod -s iomemory-vsl > /dev/null

Summarise/profile system calls made by command:
strace -c ls >/dev/null

List system calls made by command:
strace -f -e open ls >/dev/null

== T ==

=== tar ===

tar - GNU ‘tar’ saves many files together into a single tape or disk archive, and can restore individual files from the archive.

List tar contents:
tar -tf file.tar

Build tar:
tar -cf file.tar file1 file2 file3
tar -cf file.tar folder1
tar -cf file.tar -C folder1 . # chdir, so don't include folder in tar
cd folder1 ; tar -cf ../file.tar * # build tar of current folder, but don't include
tar -cf file.tar * # make archive of all files, will have issues second run

Extract tar:
tar -xf file.tar
tar -xf file.tar file1 # only extract file1
tar -xf file.tar -C folder1 # chdir, then extract

Options:
-h, --dereference # dereference links: (copy actual file, not link)
-A, --catenate, --concatenate # append tar files to an archive
-c, --create #create a new archive
-t, --list #list the contents of an archive
-u, --update #only append files that are newer than the existing in archive
-x, --extract, --get #extract files from an archive
-C, --directory DIR # change to directory DIR

Excludes:
# archive
tar --exclude='./folder' --exclude='./upload/folder2' somefolder -zcvf /backup/deploy.tgz
# extract
tar -xvf deploy.tgz --exclude '.htaccess'

=== time ===

time: time a process

Time a process:
time [process]

Example:
$ time sleep 10
real 0m10.006s
user 0m0.001s
sys 0m0.003s

Capture time:
$ ( time sleep 10 ) 2>&1 1>/dev/null | grep real | awk '{print $2}'
0m10.011s

Convert to Seconds:
OUTPUT=$( ( time staf $IPPREFIX$1 ping ping ) 2>&1 )
FULLTIME=$( echo "$OUTPUT" | grep real | awk '{print $2}' | awk -F . '{ print $1 }' )
MTIME=$( echo $FULLTIME | awk -F 'm' '{print $1}' )
STIME=$( echo $FULLTIME | awk -F 'm' '{print $2}' )
TOTAL_SECONDS=$(( $MTIME * 60 + $STIME ))

=== touch ===

touch - change file timestamps

create file:
touch [file]

set file time:
touch -c -t 0304050607 [file]

touch -d "2004-02-27 14:19:13.489392193 +0530" [file]
touch --date="2004-02-27 14:19:13.489392193 +0530" [file]
touch --date "2004-02-27 0:0:0" [file] # 1 hour behind?

=== tr ===

tr - translate or delete characters

Convert to upper or lower case:
... | tr [:lower:] [:upper:]
... | tr [:upper:] [:lower:]

=== tree ===

tree - list contents of directories in a tree-like format.

Directory tree:
tree

Shell script way: [http://www.centerkey.com/tree/]
ls -R | grep ":$" | sed -e 's/:$//' -e 's/[^-][^\/]*\//--/g' -e 's/^/ /' -e 's/-/|/'

Output as CSV file: [http://www.linuxquestions.org/questions/linux-software-2/utility-needed-list-folder-tree-and-files-in-text-file-501817/]
find | sed -e's/"/\\"/g' -e's/^..//' -e's/\//","/g' -e's/^/"/' -e's/$/"/' > /tmp/listing.csv

http://www.centerkey.com/tree/tree.sh:
<pre>
#######################################################
# UNIX TREE #
# Version: 2.3 #
# File: ~/apps/tree/tree.sh #
# #
# Displays Structure of Directory Hierarchy #
# ------------------------------------------------- #
# This tiny script uses "ls", "grep", and "sed" #
# in a single command to show the nesting of #
# sub-directories. The setup command for PATH #
# works with the Bash shell (the Mac OS X default). #
# #
# Setup: #
# $ cd ~/apps/tree #
# $ chmod u+x tree.sh #
# $ ln -s ~/apps/tree/tree.sh ~/bin/tree #
# $ echo "PATH=~/bin:\${PATH}" >> ~/.profile #
# #
# Usage: #
# $ tree [directory] #
# #
# Examples: #
# $ tree #
# $ tree /etc/opt #
# $ tree .. #
# #
# Public Domain Software -- Free to Use as You Like #
# http://www.centerkey.com/tree - By Dem Pilafian #
#######################################################

echo
if [ "$1" != "" ] #if parameter exists, use as base folder
then cd "$1"
fi
pwd
ls -R | grep ":$" | \
sed -e 's/:$//' -e 's/[^-][^\/]*\//--/g' -e 's/^/ /' -e 's/-/|/'
# 1st sed: remove colons
# 2nd sed: replace higher level folder names with dashes
# 3rd sed: indent graph three spaces
# 4th sed: replace first dash with a vertical bar
if [ `ls -F -1 | grep "/" | wc -l` = 0 ] # check if no folders
then echo " -> no sub-directories"
fi
echo
exit
</pre>

== U ==

=== ulimit ===

ulimit - Provides control over the resources available to the shell and to processes started by it, on systems that allow such control.

The default maximum open files (file descriptors) on a Redhat Linux system is 1024 per session. This is set here:
/etc/security/limits.d/90-nproc.conf

See all of the current soft limits: [http://www.eriephillips.com/?q=node/4]
ulimit -a
ulimit -Sa

See all of the current hard limits: [http://www.eriephillips.com/?q=node/4]
ulimit -Ha

To see the current session limit:
ulimit -n

To see the system limit:
cat /proc/sys/fs/file-max

To set the max to half the system limit:
ulimit -n $(( `cat /proc/sys/fs/file-max` / 2 ))

Umlimited?

The system file descriptor limit is set in /proc/sys/fs/file-max. The following command will increase the limit to 65535:
echo 65535 > /proc/sys/fs/file-max

You should then be able to increase the file descriptor limits using:
ulimit -n unlimited

This did not work for me.

A bash forkbomb [http://www.linuxhowtos.org/Tips%20and%20Tricks/ulimit.htm]
$ :(){ :|:& };:

References:
*[http://www.cyberciti.biz/faq/linux-increase-the-maximum-number-of-open-files/ Linux increase the maximum number of open files or file descriptors]
*[http://www.xenoclast.org/doc/benchmark/HTTP-benchmarking-HOWTO/node7.html Performance tuning]
*[http://www.linuxhowtos.org/Tips%20and%20Tricks/ulimit.htm Linux Howtos: Tips and Tricks -> ulimit and sysctl]

== V ==

== W ==

== X ==

== Y ==

== Z ==

== keywords ==

[[Category:Linux]]

Linux/Tools - Revision history

Kenneth: /* mkfs */