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Exim Error: Ratelimit database not available

Nov 18th

Posted by Clayton in Linux

8 comments

2009-07-20 21:58:07 Failed to get write lock for /var/spool/exim/db/ratelimit.lockfile: timed out
2008-07-20 21:58:07 H=[xx.xx.xx.xx] temporarily rejected connection in “connect” ACL: ratelimit database not available

To fix such an error , the exim cache database on the server side needs to be clear off to stop this message. More >

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exim, Linux, ratelimit, SSH

Creating an extracting tar files

Nov 7th

Posted by Clayton in Linux

3 comments

The most common compressed archive file format in Linux is the tar.gz format. Tar file is an archive file format. Tar.gz is a compressed tar file.

How to create a compressed tar.gz file from a folder or file in Linux?

In order to create a compressed tar.gz archive from a folder/file we need to run the following tar command:

tar -czf new-tar-file-name.tar.gz file-or-folder-to-archive

Here is the command explanation:

  • tar – the tar command.
  • c – create new archive.
  • z – compress the archive using gzip.
  • f – use archive file.
  • new-tar-file-name.tar.gz – the name of the tar.gz to create.
  • file-or-folder-to-archive – the name of the folder we want to archive.

More >

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compress folder, decompress folder, gzip, SSH, tar, tar.gz

cPanel Icon Missing From WHM List Accounts

Nov 3rd

Posted by Clayton in Tutorial

1 comment

I came across an issue for the first time where the cPanel icon was missing in the list accounts section. After digging around WHM, I found where the function was disabled.

  • Log into WHM
  • Select “Tweak Settings”
  • Uncheck the box next to “Disable login with root or reseller password into the users’ cPanel interface. Also disable switch account dropdown in themes with switch account feature”
  • Click save

After hitting save, you can go back to the list account section and the cPanel icon will be back.

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cPanel, WHM

pty, ptyp, and tty errors

Nov 2nd

Posted by Clayton in Linux

No comments

So I came across this error for the first time today when trying to SSH directly into a clients VPS.

login as: root
root@server’s password:
Server refused to allocate pty
stdin: is not a tty

After a quick google search I came across the fix.

[root@node /]# vzlist -a
VEID      NPROC STATUS  IP_ADDR         HOSTNAME
1337         78 running 69.10.59.80     grumpy.thelinuxnoob.com
[root@node /]# vzctl exec 1337 /sbin/MAKEDEV ptyp
[root@node /]# vzctl exec 1337 /sbin/MAKEDEV tty
[root@node /]# vzctl exec 1337 /sbin/MAKEDEV pty

The issue should now be resolved and you can SSH into the VPS.

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root, SSH, vps

Install Perl

Oct 22nd

Posted by Clayton in Linux

No comments

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

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perl, SSH

Upgrade MySQL4 to MySQL5 on cPanel server

Oct 21st

Posted by Clayton in Linux

3 comments

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 :)

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cPanel, MySQL, SSH, WHM

Disable root SSH access

Oct 20th

Posted by Clayton in Linux

3 comments

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!

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root, SSH, su

Screen in SSH

Oct 19th

Posted by Clayton in Linux

1 comment

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 :

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screen, SSH

Server time keeps resetting

Oct 16th

Posted by Clayton in Linux

No comments

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 :)

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SSH, time

Hide your Shell commands

Oct 15th

Posted by Clayton in Linux

No comments

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 :)

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