There are some tips and tricks which I use

Unix utils tricks

sed

Replace \n in any system

sed -e ':a;N;$!ba;s/\n//g;s/0d0a/\n/g'

find

Find all files changed in the interval

find ./ -newermt 2015-07-20 ! -newermt 2015-07-28

bash

Be sure the line contains at the end

oleg="hello.ending"
echo ${^${oleg}%%.ending}".ending"
hello.ending
oleg="hello"
echo ${^${oleg}%%.ending}".ending"
hello.ending

iptables

Block every outgoing connection

iptables -A OUTPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -j REJECT

Redirect everything from specific host to another port on localhost

iptables -t nat -A PREROUTING -s <from>/32 -p tcp --dport 80 -j DNAT --to-destination <to>:42424

if you are using localhost ip as destination, you must enable sysctl -w net.ipv4.conf.eth0.route_localnet=1 or make it proper:

iptables -t nat -A PREROUTING -s <from>/32 -p tcp --dport 80 -j REDIRECT --to-port 42424

ssh

Forward to localhost

ssh -v -L 127.0.0.1:1527:127.0.0.1:1527 server

Forward through one more server

ssh -L 8080:real_server:8080 control

Apply patch

patch -p1 --dry-run < debian/patches/02_socket_maxconn.patch

Packages

Build

Setup build environment

python-all-dev fakeroot unzip python-stdeb dh-python devscripts

Pack the package:

dpkg-deb -b ${PACKAGEDIR} ${WORKDIR}

Rebuild debian package

dpkg-source -x <package>.dsc
dpkg-buildpackage -rfakeroot -uc -us -sa -j3

Rebuld pip to deb:

package='Flask-Profile-0.2'
py2dsc -m 'Oleg Obleukhov <leoleovich@something>' ./${package}.tar.gz && cd deb_dist/${package} && DEB_BUILD_OPTIONS=nocheck debuild -i -us -uc -b

Rebuild from source

wget http://http.debian.net/debian/pool/main/d/dbus/dbus_${SHORT_VERSION}.orig.tar.gz -O ${WORKDIR}/dbus.orig.tar.gz wget http://http.debian.net/debian/pool/main/d/dbus/dbus_${version}.debian.tar.xz -O ${WORKDIR}/dbus.debian.tar.xz tar -xzf dbus.orig.tar.gz tar -xf dbus.debian.tar.xz -C dbus-${SHORT_VERSION}

update changelog

cd ${WORKDIR}/dbus-${SHORT_VERSION} debuild -b -uc -us

Installation

Check the source of package

apt-cache policy nginx

Web servers

Htpasswd

Generate crypt password for htpasswd

openssl passwd -apr1 12345 # md5
openssl passwd -crypt 12345 # crypt (only up to 8 chars will be there)

Network

Routes

Change default route

ip r change default via 10.0.0.240 dev eth0

Tshark

Analyse pcap

tshark -T fields -e ip.src -r web03.out.pcap  | sort | uniq -c

Tcpdump

Top hosts connecting

tcpdump -p -r ddos.pcap | awk '{print $3}' | sort | uniq -c | sort -n

Filesystem

Permissions

Fully copy permissions from one directory to another

getfacl -a it | setfacl -d -M- it-ro/

Concurrent Versions Systems

Git

Config to rebase branch in master

git config branch.master.rebase true
git config —global branch.autosetuprebase always

Go back to the commmit (it will stay)

git reset --hard b75b34e 
git push -f

Update commint message before push

git ci --amend

Databases

Mysql

Backup from live DB using maximum compression

working_master$ innobackupex --slave-info --safe-slave-backup --parallel=8 --compress --compress-threads=8 --stream=xbstream ./ | ssh -o StrictHostKeyChecking=no <broken_slave> "xbstream -xC /var/lib/mysql/"
broken_slave$ find /var/lib/mysql -name '*.qp' | while read f ; do (qpress -dv $f $(dirname $f) && rm $f)&  done

Postgres

Kill old/slow query

select * from pg_stat_activity order BY xact_start limit 10;
select pg_terminate_backend(16796);

Get list of tables

psql sonar -tXAqc "select relname from pg_catalog.pg_class where relkind = 'r' and relnamespace=2200"  | cat

Rabbitmq

Clear policies

rabbitmqctl list_vhosts -q | while read q ; do rabbitmqctl list_policies -q -p $q | while read p ; do echo "${p}" | awk '{print $2}' | while read c ; do rabbitmqctl clear_policy -p $q "${c}" ; done ; done ; done

Virtualization

KVM

virsh migrate --live --copy-storage-all --persistent --undefinesource --change-protection --auto-converge --domain <VM> --abort-on-error --desturi qemu+ssh://<HV address>/system --timeout 600

leoleovich/tricks