sps's questions

I enabled ufw firewall with the following command:

$ sudo ufw enable
Firewall is active and enabled on system startup
$

Now while I look at the status:

$ sudo ufw status verbose 
Status: active
Logging: on (low)
Default: deny (incoming), allow (outgoing), disabled (routed)
New profiles: skip 
$

It says deny (incoming). But I cannot understand what that means.

Does it mean:

Deny any packet which is incoming. (i.e. Deny any packet which is incoming regardless of source and destination ip and port address)

If the above is true, then I am wondering how am i able to browse internet. Because there will be many incoming packets from web-pages I visit. If every incoming packet is denied then I should not be able to surf web-pages. But I am.

If the above was not true then, then does it mean that some specific type of incoming packets that will be denied?If yes, then what kind of packets?

I have a script which simply echos current time and appends the output to a file. Below is the bash script.

#!/bin/bash
#Filename: /etc/init.d/bootlog
#Bash script to record a timestamp.
echo "Time: `date`" >> /home/foo/Documents/.boot_log
exit

I wanted to run this script every time my computer booted to runlevel 2, so I placed the above script in /etc/init.d/ directory with execute permission for root.

$ ls -l /etc/init.d/bootlog 
-rwx------ 1 root root 161 Jan 12 11:02 /etc/init.d/bootlog
$

Next, I added the required symlink as below.

$ cd /etc/rc2.d/
$ sudo ln -s /etc/init.d/bootlog S06bootlog
$ sudo ls -l /etc/rc2.d/S06bootlog 
lrwxrwxrwx 1 root root 18 Jan 12 12:34 /etc/rc2.d/S06bootlog -> /etc/init.d/bootlog
$ 

After doing the above steps I was expecting the script to run in my next reboot. However the script is NOT running during boot. I can see that because the .boot_log file is not created.

$ cd /home/foo/Documents/
$ sudo ls -l -a .boot_log
ls: cannot access .boot_log: No such file or directory
$ 

Is there any step I missed ? Or anything I did wrong ?

I can see the download and upload speed for all interfaces using glances. In the network section we can see the Rx/s and Tx/s columns where I can see the value in Mbps.

However I want to store this value in a variable. Is there any other command, which gives the current speed (bps, or Kbps, or Mbps) so that I can save that value in a variable in a bash script ?

I want to do this for wlan0 interface.

For some services (ex: bluetooth) I have entries in both /etc/init.d/ and in /etc/init/ directory.

How do I know how this service is started ? By sysvinit or upstart ?

I am using Ubuntu 14.04.

We know that when we connect to a http server then port 80 is used in server and a random port number in the client (web server).

I have three tabs opened in firefox. I have opened google, amazon, and gmail in each of those tabs respectively.

How can I see what port number is each of the http connection using. I am assuming those three tabs in firefox have three different http connection.

I am using firefox in ubuntu 14.04.

Recently, I compiled and installed kernel release 4.2.3 using below steps.

$ wget https://www.kernel.org/pub/linux/kernel/v4.x/linux-4.2.3.tar.gz 
$ tar xzvf linux-4.2.3.tar.gz
$ cd linux-4.2.3
$ make menuconfig

Then after saving the default configuration shown in menuconfig,

$ make
$ make modules_install
$ make install

After I completed above steps, I could see the below changes:

vmlinuz-4.2.3 (along with other few files) was added to /boot/ directory.

grub was updated .

Now, I have rebooted my computer, and, surprisingly, it has booted with no issues. Below is the system information now.

$ uname -a
Linux myMachine 4.2.3 #1 SMP Fri Oct 16 20:45:01 EDT 2015 x86_64 x86_64    x86_64 GNU/Linux 
$ uname -r
4.2.3
$ cat /proc/version 
Linux version 4.2.3 (sps@myMachine) (gcc version 4.8.4 (Ubuntu  4.8.4-2ubuntu1~14.04) ) #1 SMP Fri Oct 16 20:45:01 EDT 2015
$

So it looks like new kernel (4.2.3) is running in my system (Please let me know if I need to check any other command (apart from uname or cat /proc/version) to be sure about the kernel that is running).

Now here is my issue:- I don't know what issues I will face later if I keep using this kernel.

So I want to revert back and start using the previous kernel again. How do I do it ?

I can still see the old vmlinuz-3.19* (and other 3.19*) files in /boot/ and also in boot/grub/grub.cfg. But I do not know how to start using the old kernel once again ?

Bonus if I can select the kernel at boot time.

In /var/logs/auth.log I can see the unsuccessful login attempts. They are like lines below:

Oct 16 05:04:02 myMachine unix_chkpwd[15793]: password check failed for user (user1).

Now is there a way to see what password was tried exactly ? Is that information logged anywhere ?

I want to see the incorrect password that was attempted.

I am following this to learn to compile the kernel. I used

apt-get source linux-image-$(uname -r)

to download the source code of the Linux kernel I am curretly using.

After running the above command, the following files (and directories) were downloaded.

user $ ls -l
total 130972
drwxrwxr-x 27 sps sps      4096 Oct 16 03:10 linux-lts-vivid-3.19.0
-rw-rw-r--  1 sps sps  10980684 Oct  5 10:54 linux-lts-vivid_3.19.0-30.34~14.04.1.diff.gz
-rw-rw-r--  1 sps sps      7396 Oct  5 10:54 linux-lts-vivid_3.19.0-30.34~14.04.1.dsc
-rw-rw-r--  1 sps sps 123115155 May  6 21:35 linux-lts-vivid_3.19.0.orig.tar.gz
user $ 

In the same page it is mentioned:

Building the kernel is quite easy. Change your working directory to the root of the kernel source tree and then type the following commands:

But I am not sure which is the "root of the kernel source tree".

Is it the current directory (where I ran apt-get source ... and where I have the above listed files)?

Or, is it the directory:

drwxrwxr-x 27 sps sps      4096 Oct 16 03:10 linux-lts-vivid-3.19.0

or, should I extract the tarball

-rw-rw-r--  1 sps sps 123115155 May  6 21:35 linux-lts-vivid_3.19.0.orig.tar.gz

Output for uname -r:

user $ uname -r
3.19.0-30-generic
user $ 

I am following https://robots.thoughtbot.com/the-magic-behind-configure-make-make-install to learn how to use autoconf and automake to create the configure script and Makefile.

Below is the content of configure.ac file:

AC_INIT ([helloworld], [0.1], [[email protected]])
AM_INIT_AUTOMAKE
AC_PROG_CC
AC_CONFIG_FILES([Makefile])
AC_OUTPUT

However, when I run aclocal command, I get the following error.

user $ aclocal
configure.ac:2: error: AC_INIT should be called with package and version arguments
/usr/share/aclocal-1.14/init.m4:29: AM_INIT_AUTOMAKE is expanded from...
configure.ac:2: the top level
autom4te: /usr/bin/m4 failed with exit status: 1
aclocal: error: echo failed with exit status: 1
user $ 

I did google search to see if line AC_INIT ([helloworld], [0.1], [[email protected]]) was incorrect. But it looks like it is correct way to use AC_INIT.

How do I fix this ?

Also, below is the content of Makefile.am file (if this is related to the error):

AUTOMAKE_OPTIONS = foreign
bin_PROGRAMS = helloworld
helloworld_SOURCES = hello.c

I had ubuntu 14.04 with unity desktop. Then i downloaded and used compiz but messed up and now unity desktop is not usable. I dont see the menu on top or the panel on left side. Neither is the CLI available after pressing Ctrl+Alt+t.

However I can still access the CLI by pressing Ctrl+Alt+F1. Now, how can I undo any changes that compiz had applied, so that the desktop will be usable again.

I have vim editor version 7.3

However in this when I search for a test by typing :/SEARCHTEXT the cursor goes to the line containing the text which is searched, but the text itself is NOT highlighted.

I tried by typing :hlsearch but i get an error saying E492: Not an editor command: hlsearch

Is this because the vim package I have installed does not support hlsearch. If yes then can anyone please tell me which vim package should i install so that searched text will be highlighted ?

Thanks.

I am trying to figure out what is the difference between " " and ' '.

When I use them with echo they both give the same result,

sps@sps-Inspiron-N5110:~$ echo Hello    world
Hello world
sps@sps-Inspiron-N5110:~$ echo "Hello   world"
Hello   world
sps@sps-Inspiron-N5110:~$ echo 'Hello   world'
Hello   world
sps@sps-Inspiron-N5110:~$ 

Is there any specific situation where we need to use one or the other ?

Thanks.

I am trying to rename a file using find command.

I am trying to rename file-a to file-10.

To do this I first tried below command:

sps@sps-Inspiron-N5110:~$ find ~ -type f -name test-a -exec mv test-10 '{}' ';'
mv: cannot stat `test-10': No such file or directory
sps@sps-Inspiron-N5110:~$

Then I tried below:

sps@sps-Inspiron-N5110:~$ find ~ -type f -name test-a -exec mv test-a test-10 '{}' ';'
mv: target `/home/sps/test-a' is not a directory
sps@sps-Inspiron-N5110:~$

Now I cant think how to do that with find. I am trying to do this with find, because I will have many directories with same filename, and I want to change all the test-a to test-10 in one command. Anyone please suggest.

Thanks.

I have ubuntu 12.04

I installed emacs using below commands.

$ apt-get update
$ apt-get install emacs

Then, as expected, I could find emacs while searching in dash.

Next I wanted to uninstall emacs, so I did:

$ apt-get remove emacs

But still I can search emacs in dash. Also I am able to open emacs and use it.

However when I check below command.

sps@sps-Inspiron-N5110:~$ dpkg --status emacs
Package `emacs' is not installed and no info is available.
Use dpkg --info (= dpkg-deb --info) to examine archive files,
and dpkg --contents (= dpkg-deb --contents) to list their contents.
sps@sps-Inspiron-N5110:~$ 

It says emacs not installed. But how am I able to use emacs?

To correctly ask , "How to uninstall it ?"

I mean how do I get everything erased. I dont want any of these - source code (if any), or binary executable, or anything related to emacs - in my system, which was added when I did apt-get install emacs.

Thanks.

I want to install Ubuntu 14.04 on my laptop and it has amd e2 vision processor

I don't know know if my machine is 64-bit or 32-bit so I am having confusion downloading the UBUNTU version (64 or 32 bit)

Can anybody help??