misc.md

How-Tos

Serving Documents via HTTP

while true; do nc -l -p 80 -q 1 < error.html; done
while true; do { echo -e 'HTTP/1.1 200 OK\r\n'; cat index.html; } | nc -l 8080; done
python2 -m SimpleHTTPServer 8080
python3 -m http.server 8080
twistd -n web –path .
php -S localhost:8080

View markdown files in lynx

pandoc -s -f markdown -t html =(curl https://raw.github.com/cyberhouse/doc/master/README.md) | lynx -stdin
pandoc -s -f markdown -t html doc/README.md | lynx -stdin

Cookies and Login with curl

curl -d @$HOME/.credentials --cookie-jar /tmp/cjar -k https://example.com/?do=login; curl -k --cookie /tmp/cjar --cookie-jar /tmp/cjar https://example.com/foo|lynx -stdin

Get HTTP Status Code with curl

curl -s -w "%{http_code}\\n" http://www.cyberhouse.at -o /dev/null
# Add -L if you intend to follow location responses

See File Access for a Specific Path

lsof +D /var/log

Find Rogue Internet Gateways on your Network

nmap -sn 172.16.35.0/24 --script ip-forwarding --script-args="target=www.google.com"

Remote Network Protocol Analyzing with tcpdump or tshark and Wireshark

ssh server1 tcpdump -i eth3 -U -s0 -w - 'tcp port 80' | wireshark -k -w /tmp/gw.cap -b filesize:50000 -b files:10 -i -
ssh server1 'tshark -f "port !22" -w -' | wireshark -k -i -

Create Diff with remote file

diff .ssh/config <(ssh trillian 'cat .ssh/config')

Create cronjob programmatically

crontab -l > /tmp/$(whoami)-crontab
echo '* * * * * www-data /var/www/html/typo3/cli_dispatch.phpsh scheduler' >> /tmp/$(whoami)-crontab
crontab /tmp/$(whoami)-crontab
rm /tmp/$(whoami)-crontab

Forward Ports

socat TCP4-LISTEN:1234,fork TCP4:192.168.1.1:22' forwards your port   1234 to another machine's port 22. Very useful for quick NAT red

Sysstat's sar with 24h Time Format

sar -o /tmp/sarlog -A 5 >/dev/null 2>&1
LANG=C; S_TIME_FORMAT="%T; sar -f /tmp/sarlog|les

Setting and Removing the Immutable Bit

chattr +i /etc/shadow; lsattr /etc/shadow
chattr -i /etc/shadow; lsattr /etc/shadow

Add Swap Space

dd if=/dev/zero of=/path/to/swapfile count=2097152 # create 1 G file
mkswap /path/to/swapfile
swapon -p 32767 /path/to/swapfile # use with lowest priority possible

Optionally create an /etc/fstab entry:

/path/to/swapfile none	swap	sw,pri=32767	0	0

Reset Root Password, Access to Boot Loader Required

Add 1 (after one blank space) or S or Single to the kernel boot parameter to start in single mode. Reset password with passwd check if SELinux is disabled if it does not work (setenforce 0). If single user mode does not work ther is an alternative: Append init=/bin/bash to the boot options, remounting the root partition is necessary (mount -o remount,rw /).

Cut Connections from a Specific Address

cutter 10.10.0.45

Copy Disk with dd with Progress Bar and Compression

parted /dev/sda # Get the disk size first
dd if=/dev/sda | pv -s 60022480896 | pigz --fast > /media/myExternalDrive/myBackup.img

Write Image with dd with Progress Bar

IMAGE=archlinux-2014.04.01-dual.iso && dd bs=1m if=$IMAGE | /opt/local/bin/pv -s $(wc -c $IMAGE) | dd of=/dev/disk1

Get the Filesystem Age

tune2fs -l $(df -lh / |(read; awk '{print $1; exit}')) | grep -i created

Strace All Processes of a Program, e.g. Apache

ps aux|grep /usr/sbin/httpd|grep -v grep|awk '{print"-p " $2}'|xargs strace -s 10000 -f -t -r -o /tmp/strace-$(date +%F-%H%M%S)

Log Block Activity to Syslog (or dmesg, Depending on your Ssytem)

echo 1 > /proc/sys/vm/block_dump

Sorting ps Output by RSS

ps auxww | sort -nk6
# or 
ps auxww --sort +rss

Better Readable ps

ps auxwwef
# or to avoid line wraps
ps auxef

Get Buffered and Cached Read Speed of Block Device

hdparm -Tt /dev/sda

Fill Memory Up to Given Percentage

stress --vm-bytes $(awk '/MemFree/{printf "%d\n", $2 * 0.9;}'< /proc/meminfo)k --vm-keep -m 1

Using top in Batch Mode

top -b -i -d 10 >> /tmp/log/top

Simple Port Check with Bash's Built-in /dev/tcp

/bin/bash -c "echo >/dev/tcp/144.76.8.201/443 && echo 'open'"