Игорь Олемской — практические заметки по системному администрированию Linux CentOS

Before we get started, I really ought to drop this here:

Upgrading Fedora via yum is not the recommended method. Your first choice for upgrading Fedora should be to use preupgrade. Seriously.

This begs the question: When should you use another method to upgrade Fedora? What other methods are there?

You have a few other methods to get the upgrade done:

• Toss in a CD or DVD: You can upgrade via the anaconda installer provided on the CD, DVD or netinstall media. My experiences with this method for Fedora (as well as CentOS, Scientific Linux, and Red Hat) haven't been too positive, but your results may vary.
• Download the newer release's fedora-release RPM, install it with rpm, and yum upgrade: This is the really old way of doing things. Don't try this (read the next bullet).
• Use yum's distro-sync functionality: If you can't go the preupgrade route, I'd recommend giving this a try. However, leave plenty of time to fix small glitches after it's done (and after your first reboot).

Personal anecdote time (Keep scrolling for the meat and potatoes)
I have a dedicated server at Joe's Datacenter (love those folks) with IPMI and KVM-over-LAN access. The preupgrade method won't work for me because my /boot partition is on a software RAID volume. There's a rat's nest of a Bugzilla ticket over on Red Hat's site about this problem. I'm really only left with a live upgrade using yum.

Live yum upgrade process
Before even beginning the upgrade, I double-checked that I'd applied all of the available updates for my server. Once that was done, I realized I was one kernel revision behind and I rebooted to ensure I was in the latest Fedora 15 kernel.

A good practice here is to run package-cleanup --orphans (it's in the yum-utils package) to find any packages which don't exist on any Fedora mirrors. In my case, I had two old kernels and a JungleDisk package. I removed the two old kernels (probably wasn't necessary) and left JungleDisk alone (it worked fine after the upgrade). If you have any external repositories, such as Livna or RPMForge, you may want to disable those until the upgrade is done. Should the initial upgrade checks bomb out, try adding as few repositories back in as possible to see if it clears up the problem.

Once you make it this far, just follow the instructions available in Fedora's documentation: Upgrading Fedora using yum. I set SELinux to permissive mode during the upgrade just in case it caused problems.

I'd recommend skipping the grub2-install portion since your original grub installation will still be present after the upgrade. If your server has EFI (not BIOS), don't use grub2 yet. Keep an eye on the previously mentioned documentation page to see if the problems get ironed out between grub2 and EFI.

Before you reboot, be sure to get a list of your active processes and daemons. After your reboot, some old SysVinit scripts will be converted into Systemd service scripts. They might not start automatically and you might need to enable and/or start some services.

New to Systemd? This will be an extremely handy resource: SysVinit to Systemd Cheatsheet.

I haven't seen too many issues after cleaning up some daemons that didn't start properly. There is a problem between asterisk and SELinux that I haven't nailed down yet but it's not a showstopper.

Good luck during your upgrades. Keep in mind that Fedora 15 could be EOL'd as early as May or June 20102 when Fedora 17 is released.

Live upgrade Fedora 15 to Fedora 16 using yum is a post from: Major Hayden's Racker Hacker blog.

Thanks for following the blog via the RSS feed. Please don't copy my posts or quote portions of them without attribution.

Fedora 15 was released with some updates to allow for consistent network device names. Once it's installed, you'll end up with network devices that are named something other than eth0, eth1, and so on.

For example, all onboard ethernet adapters are labeled as emX (em1, em2...) and all PCI ethernet adapters are labeled as pXpX (p[slot]p[port], like p7p1 for port 1 on slot 7). Ethernet devices within Xen virtual machines aren't adjusted.

This may make sense to people who swap out the chassis on servers regularly and they don't want to mess with hard-coding MAC addresses in network configuration files. Also, it should give users predictable names even if a running system's drives are inserted into a newer hardware revision of the same server.

However, I don't like this on my personal dedicated servers and I prefer to revert back to the old way of doing things. Getting back to eth0 is pretty simple and it only requires a few configuration files to be edited followed by a reboot.

First, add biosdevname=0 to your grub.conf on the kernel line:

title Fedora (2.6.40.4-5.fc15.x86_64)
	root (hd0,0)
	kernel /boot/vmlinuz-2.6.40.4-5.fc15.x86_64 ro root=/dev/md0 SYSFONT=latarcyrheb-sun16 KEYTABLE=us biosdevname=0 quiet LANG=en_US.UTF-8
	initrd /boot/initramfs-2.6.40.4-5.fc15.x86_64.img

Open /etc/udev/rules.d/70-persistent-net.rules in your favorite text editor (create it if it doesn't exist) and add in the following:

# Be sure to put your MAC addresses in the fields below
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:11:22:33:44:10", ATTR{dev_id}=="0x0", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0"
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:11:22:33:44:11", ATTR{dev_id}=="0x0", ATTR{type}=="1", KERNEL=="eth*", NAME="eth1"

Be sure to rename your ifcfg-* files in /etc/sysconfig/network-scripts/ to match the device names you've assigned. Just for good measure, I add in the MAC address in /etc/sysconfig/network-scripts/ifcfg-ethX:

...
HWADDR=00:11:22:33:44:10
...

Reboot the server and you should be back to eth0 and eth1 after a reboot.

Getting back to using eth0 in Fedora 15 is a post from: Major Hayden's Racker Hacker blog.

Thanks for following the blog via the RSS feed. Please don't copy my posts or quote portions of them without attribution.

SELinux isn't a technology that's easy to tackle for newcomers. However, there's been a lot of work to smooth out the rough edges while still keeping a tight grip on what applications and users are allowed to do on a Linux system. One of the biggest efforts has been around setroubleshoot.

The purpose behind setroubleshoot is to let users know when access has been denied, help them resolve it if necessary, and to reduce overall frustration while working through tight security restrictions in the default SELinux policies. The GUI frontend for setroubleshoot is great for users who run Linux desktops or those who run servers with a display attached. Don't worry, you can configure setroubleshoot on remote servers to send alerts elsewhere when a GUI alert isn't an option.

Install a few packages to get started:

yum install setroubleshoot{-server,-plugins,-doc}

Open /etc/setroubleshoot/setroubleshoot.conf in your favorite text editor and adjust the [email] section to fit your server:

recipients_filepath = /var/lib/setroubleshoot/email_alert_recipients
smtp_port = 25
smtp_host = localhost
from_address = selinux@myserver.com
subject = [MyServer] SELinux AVC Alert

You could probably see it coming, but you need to put the e-mail addresses for your recipients into /var/lib/setroubleshoot/email_alert_recipients:

echo "selinux@mycompany.com" >> /var/lib/setroubleshoot/email_alert_recipients

You'll notice that setroubleshoot doesn't have an init script and it doesn't exist in systemd in Fedora 15. It runs through the dbus-daemon and a quick bounce of the messagebus via its init script brings in the necessary components to run setroubleshoot:

service messagebus restart

A really easy (and safe) test is to ask sshd to bind to a non-standard port. Simply define an additional port on in your /etc/ssh/sshd_config like this:

Port 22
Port 222

When you restart sshd, it will bind to port 22 with success, but it won't be allowed to bind to port 222 (since that's blocked by SELinux as a non-standard port for the ssh_port_t port type). DON'T WORRY! Your sshd server will still be listening on port 22. If you wait a moment, you'll get an e-mail (perhaps two) that not only notify you of the denial, but they make suggestions for how to fix it:

SELinux is preventing /usr/sbin/sshd from name_bind access on the tcp_socket port 222.
 
*****  Plugin bind_ports (99.5 confidence) suggests  *************************
 
If you want to allow /usr/sbin/sshd to bind to network port 222
Then you need to modify the port type.
Do
# semanage port -a -t PORT_TYPE -p tcp 222
   where PORT_TYPE is one of the following: ...

For this particular example, the quick fix would be to run:

semanage port -a -t ssh_port_t -p tcp 222

Much of this post's information was gathered from the detailed documentation on Fedora's setroubleshoot User's FAQ as well as Dan Walsh's setroubleshoot blog post.

Receive e-mail reports for SELinux AVC denials is a post from: Major Hayden's Racker Hacker blog.

Thanks for following the blog via the RSS feed. Please don't copy my posts or quote portions of them without attribution.

I'm using SELinux more often now on my Fedora 15 installations and I came up against a peculiar issue today on a new server. My PHP installation is configured to store its sessions in memcached and I brought over some working configurations from another server. However, each time I accessed a page which tried to initiate a session, the page load would hang for about a minute and I'd find this in my apache error logs:

[Thu Sep 08 03:23:40 2011] [error] [client 11.22.33.44] PHP Warning:
Unknown: Failed to write session data (memcached). Please verify that
the current setting of session.save_path is correct (127.0.0.1:11211)
in Unknown on line 0

I ran through my usual list of checks:

• netstat showed memcached bound to the correct ports/interfaces
• memcached was running and I could reach it via telnet
• memcached-tool could connect and pull stats from memcached
• double-checked my php.ini
• tested memcached connectivity via a PHP and ruby script — they worked

Even after all that, I still couldn't figure out what was wrong. I ran strace on memcached while I ran a curl against the page which creates a session and I found something significant — memcached wasn't seeing any connections whatsoever at that time. A quick check of the lo interface with tcpdump showed the same result. Just before I threw a chair, I remembered one thing:

SELinux.

A quick check for AVC denials showed the problem:

# aureport --avc | tail -n 1
4021. 09/08/2011 03:23:38 httpd system_u:system_r:httpd_t:s0 42 tcp_socket name_connect system_u:object_r:memcache_port_t:s0 denied 31536

I'm far from being a guru on SELinux, so I leaned on audit2allow for help:

# grep memcache /var/log/audit/audit.log | audit2allow
 
#============= httpd_t ==============
#!!!! This avc can be allowed using one of the these booleans:
#     httpd_can_network_relay, httpd_can_network_memcache, httpd_can_network_connect
 
allow httpd_t memcache_port_t:tcp_socket name_connect;

The boolean we're looking for is httpd_can_network_memcache. Flipping the boolean can be done in a snap:

# setsebool -P httpd_can_network_memcache 1
# getsebool httpd_can_network_memcache
httpd_can_network_memcache --> on

After adjusting the boolean, apache was able to make connections to memcached without a hitch. My page which created sessions loaded quickly and I could see data being stored in memcached. If you want to check the status of all of the apache-related SELinux booleans, just use getsebool:

# getsebool -a | grep httpd | grep off$
allow_httpd_anon_write --> off
allow_httpd_mod_auth_ntlm_winbind --> off
allow_httpd_mod_auth_pam --> off
allow_httpd_sys_script_anon_write --> off
httpd_can_check_spam --> off
httpd_can_network_connect_cobbler --> off
httpd_can_network_connect_db --> off
httpd_can_network_relay --> off
httpd_can_sendmail --> off
httpd_dbus_avahi --> off
httpd_enable_ftp_server --> off
httpd_enable_homedirs --> off
httpd_execmem --> off
httpd_read_user_content --> off
httpd_setrlimit --> off
httpd_ssi_exec --> off
httpd_tmp_exec --> off
httpd_unified --> off
httpd_use_cifs --> off
httpd_use_gpg --> off
httpd_use_nfs --> off

If you're interested in SELinux, a good way to get your feet wet is to head over to the CentOS Wiki and review their SELinux Howtos

Getting apache, PHP, and memcached working with SELinux is a post from: Major Hayden's Racker Hacker blog.

Thanks for following the blog via the RSS feed. Please don't copy my posts or quote portions of them without attribution.

If you haven't noticed already, full Xen dom0 support was added in the Linux 3.0 kernel. This means there's no longer a need to drag patches forward from old kernels and work from special branches and git repositories when building a kernel for dom0.

Something else you might not have noticed is that the Fedora kernel team has quietly slipped Linux 3.0 into Fedora 15's update channels in disguise. Click that link, scroll down, and you'll see «Rebase to 3.0. Version reports as 2.6.40 for compatibility with older userspace.» Although I'm not a fan of calling something what it isn't (2.6.40 doesn't exist on kernel.org), I can understand some of the reasoning behind the choice.

This change makes the Xen installation on Fedora 15 pretty trivial. To get started, update your kernel to the latest if you're not already on Fedora's 2.6.40 kernels:

yum -y upgrade kernel

We need three more packages (quite a few dependencies will roll in with them):

yum -y install xen libvirt python-virtinst

The xen package reels in the hypervisor itself along with libraries and command line tools (like xl and xm). Libvirt gives us easy access to VM management with the virsh command and python-virtinst gives us the handy virt-install command to make OS installations easy.

Once those packages are installed, we need to make some adjustments in your grub configuration. Open /boot/grub/menu.lst in your text editor of choice and add something like this at the bottom:

title Fedora + Xen (2.6.40-4.fc15.x86_64)
        root (hd0,1)
	kernel /boot/xen.gz
        module /boot/vmlinuz-2.6.40-4.fc15.x86_64 ro root=/dev/sda1
        module /boot/initramfs-2.6.40-4.fc15.x86_64.img

Ensure that the root (hd0,1) is applicable to your system (adjust it if it isn't). Also, check the kernel version to ensure it matches your installed kernel and adjust the root= portion to match your root volume. Flip the default line to a value which will boot your new grub entry and ensure the timeout is set to a reasonable number if you need to temporarily switch back to your original grub entry at boot time. (Hey, we all make mistakes.)

I take one extra precaution and change the UPDATEDEFAULT=yes line to no in /etc/sysconfig/kernel. This ensures that future kernel updates don't trample the entry you've just made. Keep in mind that you'll need to manually update your grub configuration when you do kernel upgrades later.

Cross your fingers and reboot. If your system doesn't reboot properly, reboot it again and choose your old kernel from the grub menu. Double-check your configuration for fat-fingering and give it another try. If your system boots and pings but you have no output via a monitor, don't fret. There's a patch for the problem which should appear soon in Linux 3.0. The impatient can snag a kernel source RPM, add the patch file, and build a local kernel (or you can download my local build from when I did it).

Log in and verify that you booted into the dom0:

[root@xenbox ~]# xm dmesg | head -n 5
 __  __            _  _    _   _   ____     __      _ ____
 \ \/ /___ _ __   | || |  / | / | |___ \   / _| ___/ | ___|
  \  // _ \ '_ \  | || |_ | | | |__ __) | | |_ / __| |___ \
  /  \  __/ | | | |__   _|| |_| |__/ __/ _|  _| (__| |___) |
 /_/\_\___|_| |_|    |_|(_)_(_)_| |_____(_)_|  \___|_|____/

Once you're done with that, make sure libvirtd is running:

/etc/init.d/libvirtd start; chkconfig libvirtd on

Try installing a VM:

virt-install \
  --paravirt \
  --name=testvm \
  --ram=512 \
  --vcpus=4 \
  --file /dev/vmstorage/testvm \
  --graphics vnc,port=5905 --noautoconsole \
  --autostart --noreboot \
  --location=http://mirrors.kernel.org/debian/dists/squeeze/main/installer-amd64/

You should have a VM installation underway pretty quickly and it will be visible via port 5905 on the local host. Enjoy the power and freedom of your brand new type 1 hypervisor.

Xen 4.1 on Fedora 15 with Linux 3.0 is a post from: Major Hayden's Racker Hacker blog.

Thanks for following the blog via the RSS feed. Please don't copy my posts or quote portions of them without attribution.

Some might call me paranoid, but I get nervous when my package manager automatically removes a kernel. I logged into my Fedora 15 VM this morning and found this:

================================================================================
 Package        Arch           Version                   Repository        Size
================================================================================
Installing:
 kernel         x86_64         2.6.35.13-92.fc14         updates           22 M
Removing:
 kernel         x86_64         2.6.35.11-83.fc14         @updates         104 M
 
Transaction Summary
================================================================================
Install       1 Package(s)
Remove        1 Package(s)

Fedora 15's default behavior is to keep three kernels: the latest one and the two previous versions. However, this behavior may be counter-productive if you compile your own modules, or if you have compatibility issues with subsequent kernel versions.

You can change how yum handles kernel packages with some simple changes to your /etc/yum.conf. The installonly_limit option controls how many old packages are kept:

installonly_limit Number of packages listed in installonlypkgs to keep installed at the same time. Setting to 0 disables this feature. Default is '0'.

I disabled the functionality altogether by setting installonly_limit to 0:

#installonly_limit=3
installonly_limit=0

It's important to keep in mind that you will need to purge these packages from your system yourself now. Kernel packages can occupy a fair amount of disk space, so make a note to go back and clean them up when you no longer need them.

Keep all old kernels when upgrading via yum is a post from: Major Hayden's Racker Hacker blog.

Thanks for following the blog via the RSS feed. Please don't copy my posts or quote portions of them without attribution.

It's no secret that I'm a big fan of the RouterBoard network devices paired with Mikrotik's RouterOS. I discovered today that these devices offer Cisco NetFlow-compatible statistics gathering which can be directed to a Linux box running ntop. Mikrotik calls it «traffic flow» and it's much more efficient than setting up a mirrored or spanned port and then using ntop to dump traffic on that interface.

These instructions are for Fedora 15, but they should be pretty similar on most other Linux distributions. Install ntop first:

yum -y install ntop

Adjust /etc/ntop.conf so that ntop listens on something other than localhost:

# limit ntop to listening on a specific interface and port
--http-server 0.0.0.0:3000 --https-server 0.0.0.0:3001

I had to comment out the sched_yield() option to get ntop to start:

# Under certain circumstances, the sched_yield() function causes the ntop web
# server to lock up.  It shouldn't happen, but it does.  This option causes
# ntop to skip those calls, at a tiny performance penalty.
# --disable-schedyield

Set an admin password for ntop:

ntop --set-admin-password

Once you set the password, you may need to press CTRL-C to get back to a prompt in some ntop versions.

Start ntop:

/etc/init.d/ntop start

Open a web browser and open http://example.com:3000 to access the ntop interface. Roll your mouse over the Plugins menu, then NetFlow, and then click Activate. Roll your mouse over the Plugins menu again, then NetFlow, and then click Configure. Click Add NetFlow Device and fill in the following:

• Type «Mikrotik» in the NetFlow Device section and click Set Interface Name.
• Type 2055 in the Local Collector UDP Port section and click Set Port.
• Type in your router's IP/netmask in the Virtual NetFlow Interface Network Address section and click Set Interface Address.

Enabling traffic flow on the Mikrotik can be done with just two configuration lines:

/ip traffic-flow
set enabled=yes interfaces=all
/ip traffic-flow target
add address=192.168.10.65:2055 disabled=no version=5

Wait about a minute and then try reviewing some of the data in the ntop interface. Depending on the amount of traffic on your network, you might see data in as little as 10-15 seconds.

Measure traffic flows with Mikrotik's RouterOS and ntop on Fedora 15 is a post from: Major Hayden's Racker Hacker blog.

Thanks for following the blog via the RSS feed. Please don't copy my posts or quote portions of them without attribution.

As promised in one of my previous posts about dual-primary DRBD and OCFS2, I've compiled a step-by-step guide for Fedora. These instructions should be somewhat close to what you would use on CentOS or Red Hat Enterprise Linux. However, CentOS and Red Hat don't provide some of the packages needed, so you will need to use other software repositories like RPMFusion or EPEL.

In this guide, I'll be using two Fedora 14 instances in the Rackspace Cloud with separate public and private networks. The instances are called server1 and server2 to make things easier to follow.

NOTE: All of the instructions below should be done on both servers unless otherwise specified.

First, we need to set up DRBD with two primary nodes. I'll be using loop files for this setup since I don't have access to raw partitions.

yum -y install drbd-utils
dd if=/dev/zero of=/drbd-loop.img bs=1M count=1000

Put this loop file initialization init script in /etc/init.d/loop-for-drbd and finish setting it up:

chmod a+x /etc/init.d/loop-for-drbd
chkconfig loop-for-drbd on
/etc/init.d/loop-for-drbd start

Place this DRBD resource file in /etc/drbd.d/r0.res. Be sure to adjust the server names and IP addresses for your servers.

resource r0 {
	meta-disk internal;
	device /dev/drbd0;
	disk /dev/loop7;
 
	syncer { rate 1000M; }
        net {
                allow-two-primaries;
                after-sb-0pri discard-zero-changes;
                after-sb-1pri discard-secondary;
                after-sb-2pri disconnect;
        }
	startup { become-primary-on both; }
 
	on server1 { address 10.181.76.0:7789; }
	on server2 { address 10.181.76.1:7789; }
}

The net section is telling DRBD to do the following:

• allow-two-primaries — Generally, DRBD has a primary and a secondary node. In this case, we will allow both nodes to have the filesystem mounted at the same time. Do this only with a clustered filesystem. If you do this with a non-clustered filesystem like ext2/ext3/ext4 or reiserfs, you will have data corruption. Seriously!
• after-sb-0pri discard-zero-changes — DRBD detected a split-brain scenario, but none of the nodes think they're a primary. DRBD will take the newest modifications and apply them to the node that didn't have any changes.
• after-sb-1pri discard-secondary — DRBD detected a split-brain scenario, but one node is the primary and the other is the secondary. In this case, DRBD will decide that the secondary node is the victim and it will sync data from the primary to the secondary automatically.
• after-sb-2pri disconnect — DRBD detected a split-brain scenario, but it can't figure out which node has the right data. It tries to protect the consistency of both nodes by disconnecting the DRBD volume entirely. You'll have to tell DRBD which node has the valid data in order to reconnect the volume. Use extreme caution if you find yourself in this scenario.

If you'd like to read about DRBD split-brain behavior in more detail, review the documentation.

I generally turn off the usage reporting functionality in DRBD within /etc/drbd.d/global_common.conf:

global {
	usage-count no;
}

Now we can create the volume and start DRBD:

drbdadm create-md r0
/etc/init.d/drbd start && chkconfig drbd on

You may see some errors thrown about having two primaries but neither are up to date. That can be fixed by running the following command on the primary node only:

drbdsetup /dev/drbd0 primary -o

If you run cat /proc/drbd on the secondary node, you should see the DRBD sync running:

version: 8.3.8 (api:88/proto:86-94)
srcversion: 299AFE04D7AFD98B3CA0AF9
 0: cs:SyncTarget ro:Secondary/Primary ds:Inconsistent/UpToDate C r----
    ns:0 nr:210272 dw:210272 dr:0 al:0 bm:12 lo:1 pe:2682 ua:0 ap:0 ep:1 wo:b oos:813660
        [===>................] sync'ed: 20.8% (813660/1023932)K queue_delay: 0.0 ms
        finish: 0:01:30 speed: 8,976 (6,368) want: 1024,000 K/sec

Before you go any further, wait for the DRBD sync to fully finish. When it completes, it should look like this:

version: 8.3.8 (api:88/proto:86-94)
srcversion: 299AFE04D7AFD98B3CA0AF9
 0: cs:Connected ro:Secondary/Primary ds:UpToDate/UpToDate C r----
    ns:0 nr:1023932 dw:1023932 dr:0 al:0 bm:63 lo:0 pe:0 ua:0 ap:0 ep:1 wo:b oos:0

Now, on the secondary node only make it a primary node as well:

drbdadm primary r0

You should see this on the secondary node if you've done everything properly:

version: 8.3.8 (api:88/proto:86-94)
srcversion: 299AFE04D7AFD98B3CA0AF9
 0: cs:Connected ro:Primary/Primary ds:UpToDate/UpToDate C r----
    ns:1122 nr:1119 dw:2241 dr:4550 al:2 bm:1 lo:0 pe:0 ua:0 ap:0 ep:1 wo:b oos:0

We're now ready to move on to configuring OCFS2. Only one package is needed:

yum -y install ocfs2-tools

Ensure that you have your servers and their private IP addresses in /etc/hosts before proceeding. Create the /etc/ocfs2 directory and place the following configuration in /etc/ocfs2/cluster.conf (adjust the server names and IP addresses):

cluster:
	node_count = 2
	name = web
 
node:
	ip_port = 7777
	ip_address = 10.181.76.0
	number = 1
	name = server1
	cluster = web
 
node:
	ip_port = 7777
	ip_address = 10.181.76.1
	number = 2
	name = server2
	cluster = web

Now it's time to configure OCFS2. Run service ocfs2 configure and follow the prompts. Use the defaults for all of the responses except for two questions:

• Answer «y» to «Load O2CB driver on boot»
• Answer «web» to «Cluster to start on boot»

Start OCFS2 and enable it at boot up:

chkconfig o2cb on && chkconfig ocfs2 on
/etc/init.d/o2cb start && /etc/init.d/ocfs2 start

Create an OCFS2 partition on the primary node only:

mkfs.ocfs2 -L "web" /dev/drbd0

Mount the volumes and configure them to automatically mount at boot time. You might be wondering why I do the mounting within /etc/rc.local. I chose to go that route since mounting via fstab was often unreliable for me due to the incorrect ordering of events at boot time. Using rc.local allows the mounts to work properly upon every reboot.

mkdir /mnt/storage
echo "/dev/drbd0  /mnt/storage  ocfs2  noauto,noatime  0 0" >> /etc/fstab
mount /dev/drbd0
echo "mount /dev/drbd0" >> /etc/rc.local

At this point, you should be all done. If you want to test OCFS2, copy a file into your /mnt/storage mount on one node and check that it appears on the other node. If you remove it, it should be gone instantly on both nodes. This is a great opportunity to test reboots of both machines to ensure that everything comes up properly at boot time.

Dual-primary DRBD with OCFS2 is a post from: Major Hayden's Racker Hacker blog.

Thanks for following the blog via the RSS feed. Please don't copy my posts or quote portions of them without attribution.

The first day of FUDCon 2011 in Tempe is coming to a close tonight and I'm completely exhausted. As promised, I'll try to summarize the day and cover the talks which I attended.

The day started out with Jared Smith's «State of Fedora» address. The audio has already been posted on the wiki, but the speech was very positive overall. He talked about some of the struggles that have happened in the past and how they'll probably happen again in some form or another. It was pretty inspirational and you could obviously tell that people in the room were energized by it.

After the address, all of the talks were pitched in BarCamp format. It was a very efficient and entertaining way to create a schedule for the conference. Everyone had 15-20 seconds to present their talk and then they had to rush outside to post their topic on the wall. We all had the opportunity to go outside and vote for the talks that sounded interesting. Once the votes were tallied, the schedule was set and the conference was fully underway.

The first talk for me was about Marek Goldmann's BoxGrinder. (Note: If you Google for BoxGrinder, make sure that you enter it as a single word. You'll get some wild unrelated results if you use two words.) In short, BoxGrinder gives you the ability to have a kickstart-ish method for automatically building images for virtual machine environments. It's completely plugin-based, so you can have different platform and delivery plugins depending on where your VM needs to be deployed. For example, you could deploy a VM with BoxGrinder that is in a format for VMWare (platform) and is delivered to the target server via SFTP (delivery). The public cloud plugins are only compatible with Amazon's products, but I'm eager to change that during one of the upcoming hackfests.

The Sheepdog talk started up right after lunch and although it was interesting, I think it left most people with quite a few questions when it was over. However, I think people are generally apprehensive when anyone tries to do anything innovative with storage. Losing data due to a bug is a big concern and many of the questions went deeper into data safety than performance and functionality.

Next up was Dave Malcolm's talk about the different implementations of python. This was definitely an eye-opening talk for my coworker and I. Dave covered CPython, Jython, PyPy and various other implementations and compared their advantages and disadvantages. I'm still pretty new to Python (I'm clutching on to ruby, PHP and perl still), but this talk really had me thinking about which implementations are best for a particular environment or task. It was quite a bit of fun to learn about some of the deep underpinnings of Python and how they differ depending on the specific implementation.

Jeff Darcy's talk about CloudFS was very intriguing. I've been a fan of GlusterFS recently, but I eventually moved away due to a lack of enterprise features and degrading performance. Jeff is working to add in encryption and authentication without rewriting the filesystem itself. There are quite a few tricky problems involved in the encryption portion due to partial writes and general security during the handshake process. CloudFS could potentially be a network filesystem which could be shared by multiple tenants with their own individual namespaces and segregated UID's. This could be a big win for providers as they could offer up large amounts of storage in an organized fashion without too many management headaches.

We wrapped up the day of talks with Chris Lalancette's presentation about Deltacloud. In short, it's a bag of daemons that allow you to manage multiple public or private clouds. Everything from image management to provisioning are included in the project. Questions were raised about whether another application was needed since vendor-specific libraries are abundant and libcloud offers many of the same features in a simpler package.

Tonight's social event was FUDPub at ASU's Memoral Union building. The food and drinks were excellent (thanks to Rackspace!) and it was a great opportunity to relax and talk with other Fedora users and developers. We had the opportunity to meet people from around the world while playing round after round of bowling and billiards. The discussions were extremely valuable, but as I said before, it was quite tiring.

I've compiled the FUDCon photos I've taken into a Flickr photo set.

That's the end of today's summary. I'll try to keep this going tomorrow as well. Thanks for reading!

FUDCon 2011: Day One is a post from: Major Hayden's Racker Hacker blog.

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FUDCon 2011 in Tempe hasn't even fully started yet, but it's been well worth the trip already. We put quite a few names with faces (or IRC nicks with faces) and discussed our initial forays into Linux when we were young.

From what I was told last night, this is the first conference organized by folks not already working for Red Hat (even though some of them were hired on after planning was underway) and presentations are done in BarCamp format. This morning kicks off with the BarCamp pitches themselves and they are supposed to last only 20 seconds each. I'm new to this format of conferences but I'm eager to see how it works.

Quite a few people on Twitter have asked me if I could toss some summaries of some of the talks onto the blog. I will certainly try my best to do so!

Here's a sampling of the photos I've taken so far:

• iPad being used as a laptop
• List of sponsors (hey, it's Rackspace!)
• Ian Weller has a great job title
• Strange «Loaf Love» truck in the hotel parking lot
• My conference badge along with a handy QR barcode
• Sunrise over Tempe

Gearing up for FUDCon 2011 is a post from: Major Hayden's Racker Hacker blog.

Thanks for following the blog via the RSS feed. Please don't copy my posts or quote portions of them without attribution.