I had just run some simple patching on a test webserver and had some issues with PHP. Ran a few more commands and the problem went away. Until I decided to patch a production server as well.

Basically the update included an apache update, which wrecked the php modules. How do I know this?

Running Ubuntu 10.04.03 LTS
apt-get update
apt-get dist-upgrade
Load website and it prompts to download/save the PHP file instead of displaying the PHP file. Great.

Check if the PHP5 module is activated:
a2enmod php5
apache2ctl restart

Only the restart yielded this:

apache2: Syntax error on line 204 of /etc/apache2/apache2.conf: Syntax error on line 1 of /etc/apache2/mods-enabled/php5.load: Cannot load /usr/lib/apache2/modules/libphp5.so into server: /usr/lib/apache2/modules/libphp5.so: cannot open shared object file: No such file or directory

So just install the module libraries for PHP5:
apt-get install libapache2-mod-php5

This should automatically restart apache, but just for good measure you can do it again to verify there are no more errors:
apache2ctl restart

Proxmox 1.9 – not fully updated (1.9 build 6542)
Had backups set to backup snapshots of machines every day starting at 2AM. They generally took about 3 hours and would finish by 5AM.

Little did I realize that I was no longer receiving the emails saying “backup successful”. Last one was 4 weeks ago. Whoops doesn’t even start to cover that.

Checking it out it looks like the backup stalled on one of the virtual machines.
ps auxww |grep vzdump
Then just kill any PID that looks like vzdump is running.

Re-run the command to backup either from the GUI or from the command line:
vzdump --quiet --snapshot --storage STORAGE --maxfiles 5 --mailto admin 101 102 103 etc

Ubuntu 10.04.3 LTS x32 fully patched.

I needed to install SNMP so my cacti installation could work with graphing. And I thought I had already installed SNMP on the server I was testing against.

Testing from cacti:
snmpwalk -v 1 -c public IPOFSERVER

Timeout: No Response from IPOFSERVER

OK, so let me see if the process is running:
ps aux | grep snmp

root 439193 0.0 0.0 3884 616 pts/0 S+ 09:59 0:00 grep snmp

Well, looks like I need to install it:
apt-get install snmpd

The installation auto-starts the snmpd service with the default configuration file. I verified it was working with ps aux again, and the snmpd service is running under the snmp user.
On the local machine I could now run snmpwalk:
snmpwalk -v 1 -c public localhost
Which retrieved the information I wanted. Unfortunately I still could not run snmpwalk from the cacti server. Doh!

Edit the snmpd.conf file if you want a different community or RO/RW rights:
nano /etc/snmp/snmpd.conf

Otherwise, just edit the default snmpd configuration:
nano /etc/default/snmpd
Change the following line:

SNMPDOPTS=’-Lsd -Lf /dev/null -u snmp -I -smux -p /var/run/snmpd.pid 127.0.0.1′

To:

SNMPDOPTS=’-Lsd -Lf /dev/null -u snmp -I -smux -p /var/run/snmpd.pid -c /etc/snmp/snmpd.conf’

Save and quit

Restart the snmpd service:
/etc/init.d/snmpd restart

Test again:
snmpwalk -v 1 -c public IPOFSERVER

Profit.

I needed to find an easy, and fairly secure, way to allow a user to login on a website and display their current user’s disk usage. Generally I just navigate to the user’s home directory and run
du -hc
But in this case I needed it to work from the web.

By default, Ubuntu runs apache as www-data. Enter sudoers. My editor’s file is nano.
visudo
Add the following to the bottom of the file:
www-data ALL=NOPASSWD: /usr/bin/du, /usr/bin/ls, other/command
Save and quit

Now your www-data user can run those commands by running sudo command. And it will not allow the user to sudo any other commands.

My PHP page is as follows:
echo exec("sudo du -hc /mnt/ | grep " . $_SESSION["valid_user"] . "| awk '{print $1}'") . " Disk Space Used
";
Obviously the SESSION variable comes from a login page, but it’s a pretty good start for me.

I know there is a GUI for RHEL, but I still prefer to do these things via a command line.

RHEL Setup NTPd

To simply set the time to the time server (correct time one-off), use the following command:
/usr/sbin/ntpdate IP_or_ADDR_of_NTP_Server

In my case it was this command and this result:

-bash-3.2# /usr/sbin/ntpdate 10.4.0.253
18 Jan 08:16:02 ntpdate[13347]: step time server 10.4.0.253 offset 756.199630 sec

As you can see, this server was off by over 12 minutes!

If you want to edit the NTP Servers List:
nano (or vi) /etc/ntpd.conf
Add the specific time server you require
/sbin/service ntpd restart

I recently installed FreeNAS 8.x release and wanted to setup a per user quota. There is no way to set this up using the GUI front end – you can only setup a mount point quota at this time.

To setup a per user quota using the CLI, just login as root using your admin password, then issue the following commands:

zfs set userquota@USERNAME=10g SHARENAME
So in my case I had a /mnt/files filesystem, so I used:
zfs set userquota@thelibrarie=10g files

You can list the user quota
zfs list -o userquota@USERNAME SHARENAME

You can remove the user quota
zfs set userquota@USERNAME=none SHARENAME

View the current Input/Output statistics
zpool iostatzpool upgrade -v

View the current compression for all pools
zfs list -o compression