Securing Your /tmp Partition with Cpanel/WHM Published: Nov 07, 2003
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If you are renting a server then chances are you only have one big partition. Learn how to create a secure /tmp partition even while your server is already up and running on Cpanel/WHM.

Securing Your /tmp Partition with Cpanel/WHM

If you are renting a server then chances are everything is lumped in / and a small amount partitioned for /boot and some for swap. With this current setup, you have no room for making more partitions unless you have a second hard-drive. Learn how to create a secure /tmp partition even while your server is already up and running.
Recently, I found out it would be worthwhile to give /tmp it's own partition and mount it using noexec- This would protect your system from MANY local and remote exploits of rootkits being run from your /tmp folder.

What we are doing it creating a file that we will use to mount at /tmp. So log into SSH and SU to root so we may being!

cd /dev

Create 100MB file for our /tmp partition. If you need more space, make count size larger.

dd if=/dev/zero of=tmpMnt bs=1024 count=100000

Make an extended filesystem for our tmpMnt file

/sbin/mke2fs /dev/tmpMnt

Backup your /tmp dir- I had mysql.sock file that I needed to recreate the symbolic link for. Other programs may use it to store cache files or whatever.

cd /

cp -R /tmp /tmp_backup

Mount the new /tmp filesystem with noexec

mount -o loop,noexec,nosuid,rw /dev/tmpMnt /tmp

chmod 1777 /tmp

Copy everything back to new /tmp and remove backup

cp -R /tmp_backup/* /tmp/

rm -rf /tmp_backup

Now we need to add this to fstab so it mounts automatically on reboots.

pico -w /etc/fstab

You should see something like this:
/dev/hda3               /                       ext3    defaults,usrquota        1 1
/dev/hda1               /boot                   ext3    defaults        1 2
none                    /dev/pts                devpts  gid=5,mode=620  0 0
none                    /proc                   proc    defaults        0 0
none                    /dev/shm                tmpfs   defaults        0 0
/dev/hda2               swap                    swap    defaults        0 0

At the bottom add
/dev/tmpMnt             /tmp                    ext2    loop,noexec,nosuid,rw  0 0

(Each space is a tab)
Save it!
Ctrl + X and Y

Your done- /tmp is now mounted as noexec. You can sleep a little bit safer tonight. I created a hello world c++ and compiled it then moved it to /tmp. Upon trying to run it (even chmod +x'ed), it gives the following error:

bash: ./a.out: Permission denied

Yay! /tmp no longer has execute permissions :-D

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Comments (39)

  • Gravatar - Thomas Dawson
    Thomas Dawson 13:19, November 12, 2003
    mke2fs command is not recognized in my ssh. What do I do?
  • Gravatar - Ramprage
    Ramprage 15:22, November 14, 2003
    Use /sbin/mke2fs instead
  • Gravatar - kel
    kel 22:58, November 15, 2003
    How to increase the /tmp space?

    I got this error:

    Warning: Unknown(): write failed: No space left on device (28) in Unknown on line 0

    Warning: Unknown(): Failed to write session data (files). Please verify that the current setting of session.save_path is correct (/tmp) in Unknown on line 0

    Please help as soon.

  • Gravatar - Don Holeman
    Don Holeman 22:18, November 16, 2003
    I just followed these directions, pretty much flawlessly. Got one warning about it not being a block special device when I went to create the partition.

  • Gravatar - simoa
    simoa 02:10, November 17, 2003
    I run a chkrootkit and found this after I secured the /tmp partition
    Checking `aliens'...

    is this normal or I have to worry about?? PLease reply as soon thanks
  • Gravatar - Ramprage
    Ramprage 14:35, November 18, 2003
    The chkrootkit aliens found message is normal when creating a tmp from a file, no worries.
  • Gravatar - mazen
    mazen 23:42, January 6, 2004
    I make the step by step
    when I type mount command I get this message

    root@server [/]# mount -o loop,noexec,nosuid,rw /dev/tmpMnt /tmp
    mount: Could not find any loop device, and, according to /proc/devices,
    this kernel does not know about the loop device.
    (If so, then recompile or `insmod loop.o'.)
  • Gravatar - cruz
    cruz 20:37, January 9, 2004
    3 things.
    Does this break cpanel in its normal use and in updates?
    If I want to revert back to the way it was before doing this modification, how is it done?
    Do I have to reboot the server once this I implement the changes?
  • Gravatar - Mo
    Mo 12:42, January 16, 2004
    use: cp -pR /tmp /tmp_backup
    instead of : cp -R /tmp /tmp_backup

    add -p to preserve file permitions and ownership.
  • Gravatar - Shanlar
    Shanlar 09:50, April 3, 2004
    ok i made my tmp to big, how do i reverse this process? tmp keeps saying device is busy and wont umount...
  • Gravatar - Gary
    Gary 12:15, May 16, 2004
    remember though, this wont save you for losers who run scripts by perl php etc....those commands can still work in /tmp
  • Gravatar - Rona
    Rona 11:32, May 22, 2004
    Can anybody tell me now how to unsecure /tmp because when i install DigiChat it's give me this error
    root@server [/home]# sh ./Install_DigiChat.bin -i console /home
    Preparing to install...
    Extracting the JRE from the installer archive...
    Unpacking the JRE...
    Extracting the installation resources from the installer archive...
    Configuring the installer for this system's environment...

    Launching installer...

    ./Install_DigiChat.bin: /tmp/install.dir.9155/Linux/resource/jre/bin/java: /bin/sh: bad interpreter: Permission denied

    Hope to get help ... :)
  • Gravatar - ca
    ca 18:14, May 23, 2004
    I suppose you should take it out of fstab, do a server reboot and create a tmp directory again.
  • Gravatar - Michael Curtis
    Michael Curtis 16:39, May 24, 2004
    Instructions worked perfect for me other than that one warning about a block device.
    One tip, any path which exists and is owned by 'nobody'... create the directory under /tmp and make a symlink... this can be used to make any path noexec, anywhere on the server... just make sure /tmp has enough space ;)
  • Gravatar - C0NIk
    C0NIk 20:32, June 9, 2004
    well there is a better way for secure the tmp

    root@server [/]# cd scripts ; ./securetmp

    thats all and it well secure the /var/tmp as well

  • Gravatar - GIGI
    GIGI 04:38, June 17, 2004
    look this<br />
    ------------<br />
    root@localhost [~]# sh ./Install_DigiChat.bin -i console<br />
    Preparing to install...<br />
    tail: `-1' option is obsolete; use `-n 1'<br />
    Try `tail --help' for more information.<br />
    ./Install_DigiChat.bin: line 329: [: `)' expected, found -z<br />
    WARNING! The amount of /tmp disk space required and/or available<br />
    could not be determined. The installation will be attempted anyway.<br />
    Extracting the JRE from the installer archive...<br />
    Unpacking the JRE...<br />
    Extracting the installation resources from the installer archive...<br />
    Configuring the installer for this system's environment...<br />
    <br />
    Launching installer...<br />
    <br />
    ./Install_DigiChat.bin: /tmp/install.dir.3158/Linux/resource/jre/bin/java: /bin/sh: bad interpreter: Permission denied<br />
    -------<br />
    pliz help me....
  • Gravatar - Robert Greenwood
    Robert Greenwood 12:14, July 9, 2004
    You will need to increase the size of the mount
  • Gravatar - Foow
    Foow 18:15, August 23, 2004
    can you tell me why you set the /tmp partition to ext2 and not ext3?
  • Gravatar - Mark
    Mark 10:18, October 21, 2004
    i already run /scripts/securetmp from cpanel, but it seem that /tmp still not secured, can i use this tutorial while i already run /scripts/securetmp?
  • Gravatar - JLChafardet
    JLChafardet 08:10, November 3, 2004
    have any one tried this over Plesk Based webservers?<br />
    <br />
    if yes, please let me know if there is any change.<br />
    <br />
    regards,<br />
    <br />
  • Gravatar - Sotek
    Sotek 15:58, November 10, 2004
    change this:<br />
    <br />
    code:<br />
    chmod 0777 /tmp<br />
    <br />
    and put this:<br />
    <br />
    chmod 1777 /tmp<br />
    <br />
    beacuse you need to set the bit who lets everyone write on /tmp
  • Gravatar - kaveh
    kaveh 16:29, December 17, 2004
    hi<br />
    how can i resize the partition ? <br />
    97% full !!!!
  • Gravatar - Big AL
    Big AL 03:11, February 25, 2005
    you can't resize a partition, just move things to /home/tmp and link /tmp to /home/tmp via ln -s /home/tmp /tmp
  • Gravatar - Mateus
    Mateus 20:45, March 7, 2005
    Hi, thanks for this tuto..<br />
    But, i already have this partition <br />
    LABEL=/tmp /tmp ext3 defaults 1 2<br />
    <br />
    my server is in theplanet and is the default mount for them.. how can i modify this ? thank you!
  • Gravatar - Lechoad
    Lechoad 07:11, April 19, 2005
    how do you undo this?
  • Gravatar - netkinetics
    netkinetics 20:19, July 21, 2005
    Change defaults to say noexec,nosuid if you already have a seperate /tmp partition.<br />
    <br />
    Then umount / mount it again. <br />
    <br />
    Also do the same with the /dev/shm mount.<br />
    <br />
    Don't forget to secure /usr/local/apache/proxy, its 777 and owned by nobdoy after every apache build on cpanel servers. Change it to 0400 and owned by root.root , or safely remove it. If you use mod_proxy you should setup another loop device like in this tutorial and mount it to /usr/local/apache/proxy to run your proxy safely. <br />
    <br />
  • Gravatar - rayan
    rayan 12:14, July 25, 2005
    hi<br />
    ist same steps for directadmin control panel?<br />
  • Gravatar - Steve
    Steve 18:22, July 26, 2005
    Yeah it should be the same Rayan, it's not control panel reliant.<br />
  • Gravatar - David
    David 21:55, July 31, 2005
    Can i add the "noexec" just by changing the fstab?
  • Gravatar - complex
    complex 05:02, December 25, 2005
    Just in case anyone wants to do this with FreeBSD, see this page (example 16-5 or 16-7):<br />
    <br />
  • Gravatar - Kapil
    Kapil 20:23, April 1, 2006
    If you have cpanel for freebsd, then just run the script /tmp/securetmp<br />
    <br />
  • Gravatar - Mateus
    Mateus 05:18, May 16, 2006
    Securetmp from cpanel does not work well, it will not protect you /tmp dir, and, this won't protect your tmp from executing Perl Scripts!.. :/
  • Gravatar - M.S.
    M.S. 03:54, June 6, 2006
    Would you whiners stop bitching and pick up a manual? This guy was kind enough to offer you a solution. So STFU. As for the perl/php errors, just edit your php.ini and make sure safe mode is on, sql safe mode is on, and make sure that url_fopen and file uploads are off. you'll be good to go.
  • Gravatar - xkasi
    xkasi 14:27, June 28, 2006
    To increase the /tmp size just redo the tutorial with a bigger count and an different filename.<br />
    e.g: <br />
    dd if=/dev/zero of=tmpMnt2 bs=1024 count=2000000<br />
    <br />
  • Gravatar - Vijay
    Vijay 13:13, October 13, 2006
    Hi,<br />
    <br />
    /scripts/securetmp<br />
    Would you like to secure /tmp & /var/tmp at boot time? (y/n) y<br />
    Would you like to secure /tmp & /var/tmp now? (y/n) y<br />
    Securing /tmp & /var/tmp<br />
    /tmp is already secure<br />
    /var/tmp is already secure<br />
    Process Complete.<br />
    <br />
    But fstab does not show noexec,<br />
    # cat /etc/fstab<br />
    # This file is edited by fstab-sync - see 'man fstab-sync' for details<br />
    LABEL=/tmp /tmp ext3 defaults 1 2<br />
    <br />
    I request others to verify whether following method is correct for CPanel 10.8. ?<br />
    <br />
    1) Because cpanel installed with /tmp saperate partition. - we do not need to change/recreate partition & copy.<br />
    2) modify /etc/fstab to following.<br />
    LABEL=/tmp /tmp ext3 loop,noexec,nosuid,rw 0 0<br />
    3) reboot server.<br />
  • Gravatar - steve
    steve 23:40, January 4, 2007
    Use this to create a 512 MB /tmp parition<br />
    <br />
    dd if=/dev/zero of=tmpMnt bs=1024 count=2097152
  • Gravatar - Daniel
    Daniel 16:56, March 8, 2008
    Which way increase space folder / tmp? <br />
    I created folder / tmp with 100MB. <br />
    Now folder / tmp fills fast. <br />
    I need to increase 2GB. <br />
    Someone can help me?
  • Gravatar - Rick
    Rick 03:51, June 7, 2008
    I just wanted to say thanks for this tutorial! My /tmp partition was created too small, and my /home partition is huge, so I used your tutorial to mount a new tmp partition inside my /home directory. Worked like a charm, thanks a bunch! :)
  • Gravatar - guy
    guy 00:41, September 10, 2008
    so does this just create another tmp folder in /dev rather than /var/tmpDSK or something? how does everything forward to this folder rather than the old just /tmp? I don't quite understand, thanks.

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