Max Koretskyi's questions

I want to install a particular version of Chrome from the official Google's repository. This is how I install Chrome now:

RUN apt-get update \
    && apt-get install -y wget gnupg \
    && wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | apt-key add - \
    && sh -c 'echo "deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main" >> /etc/apt/sources.list.d/google.list' \
    && apt-get update \
    && apt-get install -y google-chrome-stable fonts-ipafont-gothic fonts-wqy-zenhei fonts-thai-tlwg fonts-khmeros fonts-kacst fonts-freefont-ttf libxss1 \
      --no-install-recommends \
    && rm -rf /var/lib/apt/lists/*

As I undersand, this is the repository entry:

http://dl.google.com/linux/chrome/deb/ stable main

according to the format described here:

deb http://site.example.com/debian distribution component1 component2 component3

So here it uses stable as distribution, and main as a component. Stable is supposed to the version, but maybe it's a metapackage that points to the latest? But I can't figure out how to see what versions are available in this repository?

When I install it I see the following output, particularly this line:

The following packages will be upgraded:
  google-chrome-stable
1 upgraded, 0 newly installed, 0 to remove and 52 not upgraded.
Need to get 105 MB of archives.
After this operation, 3688 kB of additional disk space will be used.
Get:1 https://dl.google.com/linux/chrome/deb stable/main amd64 google-chrome-stable amd64 120.0.6099.71-1 [105 MB]

so it somehow knows that the latest is 120.0.6099.71-1 and the repository link becomes this:

https://dl.google.com/linux/chrome/deb stable/main amd64 google-chrome-stable amd64 120.0.6099.71-1

I've just installed Ubuntu and my user is a superuser which can execute commands with sudo. So I thought this user is added in /etc/sudoers file. But it seems it's not there:

#
# This file MUST be edited with the 'visudo' command as root.
#
# Please consider adding local content in /etc/sudoers.d/ instead of
# directly modifying this file.
#
# See the man page for details on how to write a sudoers file.
#
Defaults        env_reset
Defaults        mail_badpass
Defaults        secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin"

# Host alias specification

# User alias specification

# Cmnd alias specification

# User privilege specification
root    ALL=(ALL:ALL) ALL

# Members of the admin group may gain root privileges
%admin ALL=(ALL) ALL

# Allow members of group sudo to execute any command
%sudo   ALL=(ALL:ALL) ALL

# See sudoers(5) for more information on "#include" directives:

#includedir /etc/sudoers.d

The user info:

uid=1000(someuser) gid=1000(someuser) groups=1000(someuser),4(adm),24(cdrom),27(sudo),
30(dip),46(plugdev),113(lpadmin),128(sambashare)

How did I get superuser privileges?

Today I configured ssh keys access to my server. Then I tested them and by mistake I forgot to specify the user, so instead of doing it like that:

ssh [email protected]

I did it like that

ssh myserver.combut 

I successfully logged in as username. How is that possible? How does ssh server know under which user to log me in? If it's a key, than it's possible that I'll have the same key added to multiple users, what's going to happen in this case?

I want to list all modules of nginx server by line, so I type the following:

nginx -V | tr -- - '\n'

But it doesn't put modules in lines. If I do it like this:

2>&1 nginx -V | tr -- - '\n'

it works. But why?

I'm trying to build sail_align programm by following these instructions. So far everything went OK and I've completed the last fourth step without errors:

4) sudo ./Build install
This command will install the module. 
The following perl scripts will be added to your path: sail_align, sail_align_parallel

However, when I run the following to test the installation:

sail_align -i support/data/timit_5.wav -t support/data/timit_5.txt \ 
-w support/test/local -e timit_sample_test -c config/timit_alignment.cfg

I get the message that sail_align command not found. What am I doing wrong? Here is the script of Build file:

  $progname = basename($0);
  $orig_dir = Cwd::cwd();
  my $base_dir = '/home/maximus/sail_align-master';
  if (!magic_number_matches()) {
    unless (chdir($base_dir)) {
      die ("Couldn't chdir($base_dir), aborting\n");
    }
    unless (magic_number_matches()) {
      die ("Configuration seems to be out of date, please re-run 'perl Build.PL' again.\n");
    }
  }
  unshift @INC,
    (

    );
}

close(*DATA) unless eof(*DATA); # ensure no open handles to this script

use Module::Build;
Module::Build->VERSION(q{0});

# Some platforms have problems setting $^X in shebang contexts, fix it up here
$^X = Module::Build->find_perl_interpreter;

if (-e 'Build.PL' and not Module::Build->up_to_date('Build.PL', $progname)) {
   warn "Warning: Build.PL has been altered.  You may need to run 'perl Build.PL' again.\n";
}

# This should have just enough arguments to be able to bootstrap the rest.
my $build = Module::Build->resume (
  properties => {
    config_dir => '_build',
    orig_dir => $orig_dir,
  },
);

$build->dispatch;

EDIT

echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games

locate sail_align outputs nothing

EDIT2

running find / 'sail_align' outputs the following

/home/maximus/perl5/bin/sail_align
/home/maximus/perl5/bin/sail_align_parallel
/home/maximus/sail_align-master
/home/maximus/sail_align-master/blib/script/sail_align
/home/maximus/sail_align-master/blib/script/sail_align_parallel
/home/maximus/sail_align-master/docs/sail_align_tutorial_vlsrp2011.pdf
/home/maximus/sail_align-master/docs/sail_align_tutorial_vlsrp2011.ppt
/home/maximus/sail_align-master/scripts/sail_align
/home/maximus/sail_align-master/scripts/sail_align_parallel

I'm new to linux systems and I can't really understand why wee need two operators that can redirect output: pipe as | and ouput redirection operator >? Can't we just always use the second? Most of the times I see that the pipe is used if multiple commands are chained together. If however, the output is redirected to file, as in echo 'hello' > filename, the output redirection operator is used. What am I missing here?

I've just installed Apache 2.4.7 (Ubuntu) on my Ubuntu 14.04 LTS system and can't see neither prefork nor worker settings in the /etc/apache2/apache2.conf. They are also not defined for default virtual host. Should I set them myself in apache2.conf like this?

<IfModule mpm_prefork_module>
    StartServers 2
    MinSpareServers 2
    MaxSpareServers 5
    MaxClients 200 #must be customized
    ServerLimit 200 #must be customized
    MaxRequestsPerChild 100
</IfModule>

I know I can assign the permission to write to an owner/group/others like this:

chmod u+w myfolder

Can I specify the specific user here? Some like this:

chmod username u+w myfolder

I have the following cron job:

* * * * * /home/db_backups/test.sh

which runs fine and is executed every minute. If I check with sudo grep \(CRON\) /var/log/syslog I get the following:

Jun 23 11:30:01 analytics CRON[9301]: (CRON) info (No MTA installed, discarding output)

However, if I change the executable file to inreadobase_backup.sh:

* * * * * /home/db_backups/inreadobase_backup.sh

the script is not run - I can see no records in the log. The executable file if run by itself does the job with no error. Here is the content of the file:

sudo mysqldump -h example.com -u username -ppassword dbname | gzip > db.zip

Both executable files have execution permissions given to everyone. Where should I look at to pinpoint the problem?

EDIT

The job runs and creates backups successfuly if I add to sudo crontab -e the following line:

*/5 * * * * mysqldump -h example.com -u username -ppassword dbname | gzip > db.zip

However, if I move the execution line mysqldump... db.zip to inreadobase_backup.sh file and specify it for the job:

*/5 * * * * /home/db_backups/inreadobase_backup.sh

the job doesn't create backups. I don't know how to check if it runs and what error it outputs if any. If I simply execute /home/db_backups/inreadobase_backup.sh in command line the backup is created. And the only line the file contains is this:

mysqldump -h example.com -u username -ppassword dbname | gzip > db.zip

I'm deploying my project to production server using scp command. As part of the deployment process I upload to server the .htaccess file. Locally, the environment is set to DEVELOPMENT:

#Set environment
#[PRODUCTION, STAGING, TESTING, DEVELOPMENT] 

SetEnv KOHANA_ENV 'DEVELOPMENT'

However, when uploaded to server it needs to be changed to PRODUCTION. Is there any way I can accomplish that with ssh?