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ssh / autossh

autossh -M 0 -i .ssh/id_rsa-host -v -o "BatchMode yes" -o "ServerAliveInterval 10" -o "ServerAliveCountMax 3" -L 12875: user@host

ssh -i .ssh/id_rsa-host -N -T -v -o "BatchMode yes" -L 12876: user@host

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


  • -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>

Useful apps


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


  • ccze

Cleaning useless Debian items:

  • localepurge
  • deborphan
  • debfoster


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


  • dbench


  • cadaver
  • nd

HDD/ACPI monitoring:

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


  • stdout and/or stderr:
i>&j - send file descriptor i to j
1>&2 - send stdout to stderr
2>&1 - send stderr to stdout

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 (Bash v4)
foo 2>&1 | bar    - pipe stdout AND stderr into bar

command1 2> file1 - send stderr to file1

Counting files

find . -type f ¦ wc -l 


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


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


scriptreplay tutorial.timing tutorial.session

Prevent screen blanking

setterm -blank 0


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
z compress
X keep extended attributes
P --partial --progress

-e ssh use ssh with user@host:path

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>



Use in conjuction with environment variables:

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


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 $1 2>/dev/null
  • Nice terminal colours:
export PAGER='less -R -s -i'
# Blink
export LESS_TERMCAP_mb=$'\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'


  • Correct permissions for generated statistics:
su -c "/usr/lib/cgi-bin/ -update -config=<config> -LogFile=<log>" www-data



  • Gateway blocks BiPAC 7800N (RX, corrected, uncorrected, TX):
snmpget -v 2c -c public gateway . . . .

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



HDD Recovery Resources

  • To enumerate all partitions on all connected devices:
fdisk -l
  • For GRUB version <= 1, after editing /boot/grub/ and /boot/grub/menu.list (this is updated by update-grub):
grub-install <device>
  • Remember to mkswap on new linux-swap partition before swapon'.
  • How to install GRUB via grub: [1]
  • pivot_root for invoking older version of grub on recovered file system: [2]
  • gparted will automatically call relevant file system resize programs (e.g. resize2fs)
  • parted commands: [3]
  • Calculating size for mkpart command in parted when creating new partition: [4]
  • Forum thread on recovery: [5] [6]
  • Ext2/3 file system information, and mounting using alternate superblock: [7] [8] [9] [10]
    • May need to change order of arguments supplied to mount in order that it honours sb option, otherwise might try using usual superblock. Check output of dmesg or kern.log to see what file system driver reports.

Notes on distributions/environments


  • Architecture mismatch (e.g. booting with 32-bit kernel, but loading 64-bit installation, or vice versa) binfmt-464c

Linux Mint

  • MATE vs Cinnamon: [11]
    • MATE (fork from GNOME 2)
    • Cinnamon (fork from GNOME 3)
  • LMDE 201204
    • 'mint' and 'root' password only blanked when using UNetbootin to create Live USB image (Lili and Universal USB Installer didn't work) [12] [13]
    • Use live not casper for boot argument, and name of persistent loopback virtual filesystem file or partition

Live USB

Additional resources required by packages

  • Google Earth
    • Install additional fonts to correct default GUI font
apt-get install ttf-mscorefonts-install

git & ssh