Linux commands hodgepodge (I)

This post is an unusual one. The reader will not find a line of thought in it but rather a collection of command lines and telegraphic recommendations for some configuration files in the Linux (more specifically, Ubuntu) Universe.

Happy command line experience!



- To open a X session via ssh
$ ssh -X -p xxxx usernameh@ipaddressorname

- Enable networking in Linux
# route add -net 192.168.x.y netmask 255.255.255.0 gw 192.168.a.b dev eth0

- How to quickly install sshd
# apt-get install openssh-server

- Sshd to start at boot time in Debian flavours
# update-rc.d ssh defaults

- Sshd not to start at boot time in Debian flavours
# update-rc.d ssh remove

- Where to configure sshd?
# gedit (or vi) (or pico) /etc/ssh/sshd_config

- And there, some configuration settings are

X11Forwarding yes
Port xxxx
PermitRootLogin no
LogLevel VERBOSE

- How to start the sshd service
# service ssh start (or the old way /etc/init.d/ssh start)

- How to stop the ssh service
# service ssh stop (or the old way /etc/init.d/ssh stop)

- Networking to start at boot time in Debian flavours
# update-rc.d networking defaults

- Networking not to start at boot time in Debian flavours
# update-rc.d networking remove

- How to tunnel via ssh
$ ssh -p xxxx -L aaaa:localhost:bbbb username@ipaddressorname
bbbb is the local port
aaaa is the remote port

- How to disable the firestarter firewall at startup time
mv /init.d/firestarter /init.d/firestarter.old (to change the name)

- How to recover gnome GUI in the latest Ubuntu versions
# apt-get install gnome-session-fallback

- How to copy from a hard disk to an external memory storage
dd if=/dev/sda2 of=/media/externalstoragename/backupfilename.dd bs=64k conv=notrunc,noerror

- How to delete a USB memory storage
sudo dd if=/dev/zero of=/dev/sdb bs=64k

- How to install grub
# grub-install devicename

- In case there is a need to open a firewall in win7
netsh firewall set portopening protocol=TCP port=xxx name=ruleportxxx mode=ENABLE profile=All

- How to copy a file via ssh
$scp -P xxxx /source/file user@remotehost:/destination/file

- Copying files over ssh using dd (directories need to exist)
$ dd if=./yourlocalfiletocopy | ssh -p xxxx username@fqdn dd of=/path/filename



- Copying files over ssh using dd (directories need to exist) -alternative way
$ dd if=./filetotransfer | ssh username@fqdn dd "of=/destinationpath/filename"

- Copying files from the ssh server to local using dd via ssh (directories need to exist)
$ ssh -p xxxx username@fqdn 'dd if=/pathtofileinsshserver/filename' | dd of=./pathtolocaldestination/filename

- How to install 7z crypto compressing solution
# apt-get install p7zip

- How to compress a file or directory
$ 7z a destinationfile.7z ./folderorfiletocompress

- How to decompress (no full path)
$ 7z e compressedfile.7z

- How to decompress (full path)
$ 7z x compressedfile.7z

- How to compress a file or directory using a password and in volumes
$ 7z a -p -v1g destinationfile.7z ./folderorfiletocompress

- How to stop a machine via ssh (if you are using lightdm, shutdown will not power the machine off)
# poweroff --verbose

- How to reboot a machine via ssh
# reboot --verbose

- ssh login without a password
Good summary here

- How to see real time the iptables logs in linux
# /sbin/iptables -L

- How to see whether the firestarter FW is running
# /etc/init.d/firestarter status

- How to see whether iptables is running
$ lsmod | grep iptable

- How to lock the Ubuntu box using the keyboard
CTRL + Alt + L

- Where are authentication related logs in linux?
$ less (or pico) /var/log/auth.log

- If there is a need to check previous zipped logs
# gzip -d syslog.2.gz

- Executing a terminal server that is not linked to a user in Ubuntu
# x11vnc  -safer -localhost -nopw -once -auth /var/run/lightdm/root/:0 -noxrecord -bg -rfbport xxxx

- Executing a terminal server that is not linked to a user in Ubuntu (a more verbose one)
# /usr/bin/x11vnc -safer-auth /var/run/lightdm/root/:0 -noxrecord -noxfixes -noxdamage -forever (or once) -bg -rfbport xxxx -o /tmp/x11vnc.log

- Executing a terminal server that is linked to a user session
$ x11vnc -safer -localhost -nopw -once -display :0

- Typical rc.local file for paranoid ones
ifconfig eth0 192.168.xxx.xxx netmask 255.255.255.0
route add default gw 192.168.y.y eth0
arp -s 192.168.y.y 00:router:mac:address
/etc/init.d/ddclient start
rfkill block bluetooth
rfkill block wifi
rfkill block wwan

- If you are encrypting the home drive and using keys in ssh to log in...
place the .authorised_keys file outside the crypto zone as you can read here
... in addition to that, add these 2 lines to the .profile file to speed up decryption at log-in time:
ecryptfs-mount-private
cd /home/username

- Who is in the system
$ who

- Who logged in last
$ last -a




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