Install Perl

Published on October 22, 2009 in Linux, SSH and Tutorial. 0 Comments Tags: , .

Very simple install, only 4 commands via SSH and takes about 20 minutes for the install to complete.

wget http://layer1.cpanel.net/perl588installer.tar.gz
tar -xvzf perl588installer.tar.gz
cd perl588installer
./install

Upgrade MySQL4 to MySQL5 on cPanel server

Published on October 21, 2009 in Linux, SSH, Tutorial and cPanel. 0 Comments Tags: , , , .

Upgrading MySQL versions is a quick and easy process, not much work involved. Always be sure to make a backup before you start though, just in case the upgrade fails or some other unforeseen issue arises.

cp -Rpf /var/lib/mysql /var/lib/mysql.BAK
Login to WHM –> Tweak Settings –> MySQL -> 5.0  and Save settings
/scripts/mysqlup –force
/scripts/perlinstaller –force Bundle::DBD::mysql
/scripts/realperlinstaller –force DBD::mysql
Recompile PHP

You’re done :)

Disable root SSH access

Published on October 20, 2009 in Linux, SSH and Tutorial. 0 Comments Tags: , , .

Allowing the root user to login directly is a major security issue, we’ll show you how to disable it so you can still login as root but just not directly, reducing the security issue.

This will force a hacker to have to guess 2 seperate passwords to gain root access.
(you do have 2 seperate passwords for admin and root right?)
What happens is you’ll first need to login as your admin user in SSH, then switch to the super user with the su command to get root.

We also will be forcing the use of SSH protocol 2, which is a newer, more secure SSH protocol
Just a couple more ways to help your server stay safe from the bad guys. If you’re using cPanel make sure you add your admin user to the ‘wheel‘ group so that you will be able to ‘su -‘ to root, otherwise you may lock yourself out of root.

1. SSH into your server as ‘admin‘ and gain root access by su

2. Copy and paste this line to edit the file for SSH logins
pico -w /etc/ssh/sshd_config

3. Find the line
Protocol 2, 1

4. Uncomment it and change it to look like
Protocol 2

5. Next, find the line
PermitRootLogin yes

6. Uncomment it and make it look like PermitRootLogin no

7. Save the file Ctrl+X then Y then enter

8. Now you can restart SSH
/etc/rc.d/init.d/sshd restart

Now, no one will be able to login to root with out first loggin in as admin and ’su -’ to root, and you will be forcing the use of a more secure protocol. Just make sure you remember both passwords!

Screen in SSH

Published on October 19, 2009 in Linux, SSH and Tutorial. 0 Comments Tags: , .

I’m short on time, but here’s a nice little tutorial on screen in SSH courtesy of Aperiodic.net.

Getting in

start a new screen session: screen
.. with session name: screen -S <name>
attach to a running session: screen -r
.. to session with name: screen -r <name>
the “ultimate attach”: screen -dRR (Attaches to a screen session. If the session is attached elsewhere, detaches that other display. If no session exists, creates one. If multiple sessions exist, uses the first one.)

Escape key

All screen commands are prefixed by an escape key, by default C-a (that’s Control-a, sometimes written ^A). To send a literal C-a to the programs in screen, use C-a a.

Getting out

detach: C-a d
detach and logout (quick exit): C-a D D
exit screen: exit all of the programs in screen.
force-exit screen: C-a C-\ (not recommended)

Help

See help: C-a ? (lists keybindings)

Window Management

create new window: C-a c
change to last-visited active window: C-a C-a (commonly used to flip-flop between two windows)
change to window by number: C-a <number> (only for windows 0 to 9)
change to window by number or name: C-a ' <number or title>
change to next window in list: C-a n or C-a <space>
change to previous window in list: C-a p
see window list: C-a ” (allows you to select a window to change to)
show window bar C-a w (if you don’t have window bar)
close current window: Close all applications in the current window (including shell)
kill current window: C-a k (not recommended)
rename current window: C-a A

Split screen

split display: C-a S
jump to next display region: C-a tab
remove current region: C-a X
remove all regions but the current one: C-a Q

Misc

redraw window: C-a C-l
enter copy mode: C-a [ (also used for viewing scrollback buffer)
paste: C-a ]
monitor window for activity: C-a M
monitor window for silence: C-a _
enter digraph: C-a C-v
lock (password protect) display: C-a x
enter screen command: C-a :

Server time keeps resetting

Published on October 16, 2009 in Linux, SSH and Tutorial. 0 Comments Tags: , .

Last night I came across a ticket where a customers time kept resetting on their dedicated server. Typically I would fix the time by using the date command because most of issues I came across the servers were only minutes off. After reading through the clients ticket history I realized that the timezone and minutes were correct, but the hour was still off. After a nice little google search I came across a post on a popular linux forum, where a member had the same issue the client was having. In the post a member suggested creating a symlink for /etc/localtime to point to the clients timezone in the /usr/share/zoneinfo folder. I figured it was worth a shot and tried this fix out, and it worked perfectly :)

Since the client was located in Pakistan, he needed the server to be set to the Asai/Karachi time zone.

root@server [/]# ln -sf /usr/share/zoneinfo/Asia/Karachi /etc/localtime

Before the symlink the time showed in EST but listed the timezone as GMT +5

root@server[/]# date
Mon Jan 26 02:46:24 GMT+5 2009
root@server[/]#

After the symlink the time showed in Asia/Karachi (or GMT +5)

root@server [/]# date
Mon Jan 26 12:48:14 PKT 2009
root@server[/]#

Your localtime file should look like this now:

lrwxrwxrwx  1 root   root       32 Jan 26 12:47 localtime -> /usr/share/zoneinfo/Asia/Karachi

I’m not entirely sure why the date wasn’t correct to begin with as the timezone was correct (+5GMT) when checking with the date command. But, things are fixed now so I really can’t complain since the customer is happy :)

Hide your Shell commands

Published on October 15, 2009 in Linux, SSH and Tutorial. 0 Comments Tags: .

Today  I came across a neat, but pointless shell command. By running the following in shell, it will hide any commands you run.

root@server2 [/]# stty -echo

In order to disable this mode, simply remove the “-” before echo.

root@server2 [/]# stty echo

I guess there really is no point to the command, though you could always mess with your coworkers if they leave their shell prompt open :)

Enable PHP5 when PHP4 is default

Published on October 14, 2009 in Linux, SSH and Tutorial. 0 Comments Tags: , , , .

The following tutorial will show how to enable PHP5 on your site, when Apache has PHP4 as default. I normally do everything through SSH, so here are the steps.

root@thelinuxnoob.com [/]# cd home/thelinux/public_html/
root@thelinuxnoob.com [~/public_html]# nano .htaccess
Add the following line to the .htaccess: AddType application/x-httpd-php5 .php
ctrl + x
ctrl + y
enter
root@thelinuxnoob.com [~/public_html]# cat .htaccess | grep php5
AddType application/x-httpd-php5 .php
root@thelinuxnoob.com [~/public_html]# chmod 644 .htaccess
root@thelinuxnoob.com [~/public_html]# chown thelinux.thelinux .htaccess
root@thelinuxnoob.com [~/public_html]#

Via FTP

Open favorite text editor
AddType application/x-httpd-php5 .php
Save as “.htaccess”
Upload through FTP client

That’s my quick tutorial of the day, tune in next time for more tutorials :)

Chattr FTW!

Published on October 13, 2009 in Linux, SSH and Tutorial. 0 Comments Tags: , , .

I’m tired of clients breaking their sites and then complaining about it saying it’s an issue with the server, when in reality it’s 100% their fault to begin with. I’ve ran into a few issues where clients needed something set in their php.ini or .htaccess in order for their site to work, such as “allow_url_fopen” or “register_globals”. So to make things easier on the client I would set these variables for them and get their site working. Normally I would not hear back from the client if they left things alone, but it seems like lately the inexperienced clients have been getting the urge to modify the changes I’ve made, thus breaking their site an either getting either a 500 or some other kind of error. To prevent something like this from happening, you can go in an change the file attributes to keep them from screwing things up by using chattr. Chattr is also useful for important files on the server, as it can prevent people from removing those critical files from the server.

The letters select the new attributes for the files: append only (a), compressed (c), no dump (d), immutable  (i),  data journalling  (j),  secure deletion (s), no tail-merging (t), undeletable (u), no atime updates (A), synchronous directory updates (D), synchronous updates (S), and top of directory hierarchy (T).

Using chattr is pretty straight forward as the syntax is not too complicated. The command below would add the A and I attributes to the file, thus making it read-only so that it cannot be deleted nor modified

chattr +ai /home/clay/public_html/.htaccess

To remove the file attributes you would simply replace the “+” with “-” like so.

chattr -ai /home/clay/public_html/.htaccess

There are other attributes that can used with chattr but “AI” are the ones I commonly use. Now you can have fun using chattr to prevent clients from changing files they shouldn’t be changing.