Bash command to print list of sequential host name

Bash command to print list of sequential host name:

for i in `seq 11 15`; do echo "server${i}"; done


this will print the following hostname:

server11
server12
server13
server14
server15

Change timezone in debian

To change timezone in debian, you can use the following 2 steps.

1. Edit /etc/timezone with your desired timezone such as America/New_York

2. run the following command as root or use sudo
  
    dpkg-reconfigure tzdata

    If you want to run it non-interactively so you can script it, use the following command:

    dpkg-reconfigure -f noninteractive tzdata

Put Linux process on the background and exit

you started a process on the foreground and need to put it in a background so you can exit the ssh shell, then you can run the following:


press [CTRL]+[Z]
bg
disown -h
exit




If you need to start a new process and put in background, you can use the nohup command as follow:

nohup ./loop.sh &

Check ethernet connection speed in Linux

Type the following command to get speed for eth0:

ethtool eth0 | less

OR

ethtool eth0 | grep -i speed

Apache not processing php in suse

If you have php installed on your suse os, but apache is not processing php page, then the following might help solve your problem:

1. edit /etc/sysconfig/apache2, on "APACHE_MODULES=" add "mod_php5"

2. Edit /etc/apache2/sysconfig.d/loadmodule.conf

Add this line for 32 bit OS
LoadModule php5_module /usr/lib/apache2/mod_php5.so

Add this line for 64 bit OS
LoadModule php5_module /usr/lib64/apache2/mod_php5.so


3. run these command
 /etc/init.d/apache2 stop
 /etc/init.d/apache2 start

Test active mode ftp in linux

Ftp is old and insecure, but some people still use it. So here's a way to test it on linux to see if your ftp server is responding to active mode ftp correctly:

for ftp:


ftp ftp-server.com
type your username
type your password
passive off          # this turn off the passive mode, then you can run ls, get, put command
ls
quit


for ftps using lftp (you can type debug to get into debug mode)

implicit (assuming port 990)


lftp ftps://ftp-server.com:990
set ftp:passive-mode off
user username
type your password 
#type ls, get, put command
ls
exit



explict (assuming port 21)


lftp ftp://ftp-server.com
set ftp:ssl-allow-anonymous yes
set ssl:verify-certificate off
set ftp:passive-mode off
set ftp:ssl-force on
set ftp:ssl-allow on
user username
type your password 
#type ls, get, put command
ls
exit

List only directories or files in a Linux/Unix directory

To list just directories, use this command:

ls -l | egrep '^d'

If you just want the directories name without detail, then use this command:

ls -l | egrep '^d' | awk '{print $NF}'



To list just files, use this command:

ls -l | egrep -v '^d'

If you just want the file names without detail, then use this command:

ls -l | egrep -v '^d' | awk '{print $NF}'

"su: No directory!" and "su: No shell" error

Problem:

You can log in as root, but when you try to switch to other user by running "su - username", you get "su: No directory!" error.

example:

command ran:

su - testuser

error:

su: No directory!

You also get "su: No shell" error when you try to run a command as a user by running " su username -c 'echo test' "

example:

su testuser -c 'echo test'

error:

su: No shell

Solution:

The permission on / is set up incorrectly. you probably have drwx for /. Other user need to have execute permission on / in order to solve this problem.

you can fix this by running this command:

chmod o+x /



Old permission:

 # ls -la /

drwx------  19 root     root          22 Sep 28  2009 .
drwx------  19 root     root          22 Sep 28  2009 ..

New permission:

# ls -la /

drwx-----x  19 root     root          22 Sep 28  2009 .
drwx-----x  19 root     root          22 Sep 28  2009 ..

Redirect nohup output to another file

Normally, nohup save the output to nohup.out file. But you can change that using the following command:

nohup some_command > nohup_new_output.out 2>&1&

Converting SSH key format

To convert ssh key in PEM format to OpenSSH format, use this command:

ssh-keygen -i -f pem_format.pub > id_rsa.pub 

To convert ssh key in OpenSSH format to PEM format, use this command:

ssh-keygen -e -f id_rsa.pub > pem_format.pub 

To see the fingerprint of the ssh key use this command:

To see the fingerprint of the ssh key, use this command:

ssh-keygen -l -f id_rsa.pub 

This will return three things:

• the bit strength
• the fingerprint
• the filename

PEM format:

---- BEGIN SSH2 PUBLIC KEY ----

Comment: "4096-bit RSA, converted from OpenSSH by user@machine_name"

AAAAB3NzaC1yc2EAAAABIwAAAgEAwrr66r8n6B8Y0zMF3dOpXEapIQD9DiYQ6D6/zwor9o

39jSkHNiMMER/GETBbzP83LOcekm02aRjo55ArO7gPPVvCXbrirJu9pkm4AC4BBre5xSLS

7soyzwbigFruM8G63jSXqpHqJ/ooi168sKMC2b0Ncsi+JlTfNYlDXJVLKEeZgZOInQyMmt

isaDTUQWTIv1snAizf4iIYENuAkGYGNCL77u5Y5VOu5eQipvFajTnps9QvUx/zdSFYn9e2

sulWM3Bxc/S4IJ67JWHVRpfJxGi3hinRBH8WQdXuUwdJJTiJHKPyYrrM7Q6Xq4TOMFtcRu

LDC6u3BXM1L0gBvHPNOnD5l2Lp5EjUkQ9CBf2j4A4gfH+iWQZyk08esAG/iwArAVxkl368

+dkbMWOXL8BN4x5zYgdzoeypQZZ2RKH780MCTSo4WQ19DP8pw+9q3bSFC9H3xYAxrKAJNW

jeTUJOTrTe+mWXXU770gYyQTxa2ycnYrlZucn1S3vsvn6eq7NZZ8NRbyv1n15Ocg+nHK4f

uKOrwPhU3NbKQwtjb0Wsxx1gAmQqIOLTpAdsrAauPxC7TPYA5qQVCphvimKuhQM/1gMV22

5JrnjspVlthCzuFYUjXOKC3wxz6FFEtwnXu3uC5bVVkmkNadJmD21gD23yk4BraGXVYpRM

IB+X+OTUUI8=

---- END SSH2 PUBLIC KEY ----

OpenSSH format:

ssh-rsa

AAAAB3NzaC1yc2EAAAABIwAAAgEAwrr66r8n6B8Y0zMF3dOpXEapIQD9DiYQ6D6/zwor9o

39jSkHNiMMER/GETBbzP83LOcekm02aRjo55ArO7gPPVvCXbrirJu9pkm4AC4BBre5xSLS

7soyzwbigFruM8G63jSXqpHqJ/ooi168sKMC2b0Ncsi+JlTfNYlDXJVLKEeZgZOInQyMmt

isaDTUQWTIv1snAizf4iIYENuAkGYGNCL77u5Y5VOu5eQipvFajTnps9QvUx/zdSFYn9e2

sulWM3Bxc/S4IJ67JWHVRpfJxGi3hinRBH8WQdXuUwdJJTiJHKPyYrrM7Q6Xq4TOMFtcRu

LDC6u3BXM1L0gBvHPNOnD5l2Lp5EjUkQ9CBf2j4A4gfH+iWQZyk08esAG/iwArAVxkl368

+dkbMWOXL8BN4x5zYgdzoeypQZZ2RKH780MCTSo4WQ19DP8pw+9q3bSFC9H3xYAxrKAJNW

jeTUJOTrTe+mWXXU770gYyQTxa2ycnYrlZucn1S3vsvn6eq7NZZ8NRbyv1n15Ocg+nHK4f

uKOrwPhU3NbKQwtjb0Wsxx1gAmQqIOLTpAdsrAauPxC7TPYA5qQVCphvimKuhQM/1gMV22

5JrnjspVlthCzuFYUjXOKC3wxz6FFEtwnXu3uC5bVVkmkNadJmD21gD23yk4BraGXVYpRM

IB+X+OTUUI8= user@machine_name