Difference between revisions of "Linux"

Revision as of 17:28, 26 January 2012

Console shortcuts

• Ctrl + Z: stop (fg/bg)
• Ctrl + Y: stop only when process tries to read input from console
• Ctrl + S/Q: XON/XOFF (Shift + PgUp/PgDn to scroll)
• Ctrl + L: clear screen
• Ctrl + A/E: beginning/end of line
• Alt + F/B: forward/back one word

Screen

• -S <session name> Start session with name
• -e <program to start>
• -r Attach
• -R Attach if possible, otherwise start new
• -ls List sessions
• -x <session name> Attach to open session
• -d (-r) Detach the elsewhere running screen (and reattach here)
• -D (-r) Detach and logout remote (and reattach here)
• -D -RR Do whatever is needed to get a screen session

^A followed by

• d detach
• c new window
• A rename window
• w list windows
• " selectable window list
• 0-9 select window 0-9
• s split (new region)
• TAB change region focus
• Q make current region only one visible
• X kill region
• ^\ kill everything (including all processes)!
• M monitor window for activity
• _ monitor window for inactivity
• a send ^A to session
• p/n previous/next window
• N show window name
• A set window name
• k kill current window
• [ copy (space to mark, Esc to exit, / or ? for search, Ctrl + S/R for incremental, "ignorecase yes")
• ] paste

•  ? list all possible commands
•  : screen command prompt
  •  :sessionname <name>
  •  :multiuser on
  •  :aclchg <user> +r "#" Read perms on all windows
  •  :acldel <user>

• http://www.bangmoney.org/presentations/screen.html
• Use on serial lines

Useful apps

Squid:

• squidtaild
• squidclient
• srg
• squidview
• calamaris
• sarg

Highlighter:

• ccze

Cleaning useless Debian items:

• localepurge
• deborphan
• debfoster

Monitoring:

• iptraf
• bmon
• atsar
• sysstat
• nmon
• mytop

Benchmarking:

• dbench

WebDAV:

• cadaver
• nd

HDD/ACPI monitoring:

• acpitail
• hddtemp
• fancontrol
• lm-sensors
• mbmon
• yacpi

Redirection

• stdout and/or stderr:

foo > bar 2>&1    - send stdout to bar, and stdout & stderr to terminal
command &>file    - send stdout AND stderr to file
command >&file    - send stdout AND stderr to file
foo 2>&1 | bar    - pipe stdout AND stderr into bar

command1 2> file1 - send stderr to file1

Counting files

find . -type f ¦ wc -l 

find

From Code Coffee:

find defaults to current directory.

find / -name 'program.c'
find /home/david -name 'index*'
find /home/david -iname 'index*' - case-insensitive

find /mp3collection -name '*.mp3' -size -5000k - less than 5MB
find / -size +10000k                           - greater than 10M

find /home/david -amin -10 -name '*.c' - access, minutes
find /home/david -atime -2 -name '*.c' - access, 24-hour periods
find /home/david -mmin -10 -name '*.c' - modified
find /home/david -mtime -2 -name '*.c'

find / -mount -name 'win*' - one file system

find /mp3-collection -name 'Metallica*' -and -size +10000k - and
find /mp3-collection -size +10000k ! -name "Metallica*"    - not
find /mp3-collection -name 'Metallica*' -or -size +10000k  - or

find / - name 'Metallica*' -exec ls -l {\}\ \; - execute command:
 substitution: {\}\
 command end: \;

Recording the screen

Recording:

script -t 2> tutorial.timing -a tutorial.session

Playback:

scriptreplay tutorial.timing tutorial.session

Prevent screen blanking

setterm -blank 0

rsync

a archive mode
v verbose
h human-readable
W whole file mode (don't use rsync algo)
d transfer directories without recursing
n dry run

For local file comparisons:

rsync -avnhW "Desktop/My Passport/Mitsubishi090109_10" "/Volumes/My Passport"

Windows drive backup:

sudo rsync -avhWd --progress --ignore-existing --exclude='System Volume Information' --exclude='$RECYCLE.BIN' sdb1/ Dagron/

NOTE: Use sudo to ensure directory times are transferred. Will fail to transfer time of root directory.

tcpdump with greater snarf size

tcpdump -s 1500 -w out-file.pcap <expression>

Scripts

• lesspipe.sh

Use in conjuction with environment variables:

export LESS=-R
export LESSOPEN="|/usr/local/bin/lesspipe.sh %s"

Script:

#!/bin/sh
case "$1" in
*.log.[0-9]*.gz) gunzip -c $1 2>/dev/null | ccze -A
        ;;
*.log|*.log.[0-9]*) cat $1 | ccze -A
        ;;
*.gz) gunzip -c $1 2>/dev/null
        ;;
esac

• Nice terminal colours:

export PAGER='less -R -s -i'
# Blink
export LESS_TERMCAP_mb=$'\E[05;31m'
# Bold
export LESS_TERMCAP_md=$'\E[01;33m'
# End above modes
export LESS_TERMCAP_me=$'\E[0m'
# End standout
export LESS_TERMCAP_se=$'\E[0m'
# Stand out
export LESS_TERMCAP_so=$'\E[00;44;33m'
# End underline
export LESS_TERMCAP_ue=$'\E[0m'
# Underline
export LESS_TERMCAP_us=$'\E[04;32m'

• Log file viewers:

sudo tail -F -n 50 --max-unchanged-stats=5 /var/log/apache2/access.log | ccze
sudo tail -F --max-unchanged-stats=5 -n 50 /var/log/squid/access.log | ccze -C
sudo tail -F --max-unchanged-stats=5 -n 100000 /var/log/auth.log 2> /dev/null | grep --line-buffered -E "(sshd).*(Accepted)" | ccze
sudo watch -d -t 'netstat -p -t | grep ESTABLISHED'

AWStats

• Correct permissions for generated statistics:

su -c "/usr/lib/cgi-bin/awstats.pl -update -config=<config> -LogFile=<log>" www-data

SNMP

snmpd.conf.html

• Gateway blocks BiPAC 7800N (RX, corrected, uncorrected, TX):

snmpget -v 2c -c public gateway .1.3.6.1.2.1.10.94.1.1.11.1.1.3 .1.3.6.1.2.1.10.94.1.1.11.1.3.3 .1.3.6.1.2.1.10.94.1.1.11.1.4.3 .1.3.6.1.2.1.10.94.1.1.11.1.2.3

RRDTool Spike Removal

• Traffic in/out:

su -c "/home/balint/bin/killspike2 traffic_in 1000000 gateway_traffic_in_32.rrd" www-data

• Gateway

su -c "/home/balint/bin/killspike2 snmp_data 1000 gateway_snmp_data_41.rrd" www-data
su -c "/home/balint/bin/killspike2 snmp_data 1000 gateway_snmp_data_42.rrd" www-data
su -c "/home/balint/bin/killspike2 snmp_data 1000 gateway_snmp_data_43.rrd" www-data
su -c "/home/balint/bin/killspike2 snmp_data 1000 gateway_snmp_data_44.rrd" www-data

• Bug with Cacti: moving elements in graph template causes connection between actual graph and data source for each element to become corrupt, so necessary to re-edit graph item and re-select correct data source for appropriate graph elements.

diff

diff -u -r --strip-trailing-cr --unidirectional-new-file -X diff.ignores <orig> <new> > <patch>

diff.ignores:

Makefile
*.o
*.cmd
*.ko
compat_autoconf.h
.*
*.bk
*.orig
*.symvers
*.mod.c
*.order
*.mk