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  • Puppet: array in parameterized classes VS using resources

    - by Luke404
    I have some use cases where I want to define multiple similar resources that should end up in a single file (via a template). As an example I'm trying to write a puppet module that will let me manage the mapping between MAC addresses and network interface names (writing udev's persistent-net-rules file from puppet), but there are also many other similar usage cases. I searched around and found that it could be done with the new parameterised classes syntax: if implemented that way it should end up being used like this: node { "myserver.example.com": class { "network::iftab": interfaces => { "eth0" => { "mac" => "ab:cd:ef:98:76:54" } "eth1" => { "mac" => "98:76:de:ad:be:ef" } } } } Not too bad, I agree, but it would rapidly explode when you manage more complex stuff (think network configurations like in this module or any other multiple-complex-resources-in-a-single-config-file stuff). In a similar question on SF someone suggested using Pienaar's puppet-concat module but I doubt it could get any better than parameterised classes. What would be really cool and clean in the configuration definition would be something like the included host type, it's usage is simple, pretty and clean and naturally maps to multiple resources that will end up being configured in a single place. Transposed to my example it would be like: node { "myserver.example.com": interface { "eth0": "mac" => "ab:cd:ef:98:76:54", "foo" => "bar", "asd" => "lol", "eth1": "mac" => "98:76:de:ad:be:ef", "foo" => "rab", "asd" => "olo", } } ...that looks much better to my eyes, even with 3x options to each resource. Should I really be passing arrays to parameterised classes, or there is a better way to do this kind of stuff? Is there some accepted consensus in the puppet [users|developers] community? By the way, I'm referring to the latest stable release of the 2.7 branch and I am not interested in compatibility with older versions.

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  • How does syslog-ng handles flush_lines(0) ?

    - by Luke404
    I wanted to make sure my syslog-ng was doing async logging. Reading through the documentation I see the flush_lines() option for file() destinations, if unspecified, will use the global default. Then I see that the global setting defaults to 0 but it doesn't explain what that means. Is it going to do synchronous logging when set to 0? is it going to buffer an unlimited number of lines (flushing just every flush_timeout() number of seconds)? is it going to bite me?

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  • Looking for an application to record audio and video on a linux "embedded" device

    - by Luke404
    I am working with a linux x86 device with limited CPU resources (as a prototype we just use a pentium-m netbook). We'd like to record video from one V4L2 device (we'll probably end up using just USB Video Class devices like all modern webcams) and one audio stream from an ALSA source. The thing will not have screen and keyboard, and obviously no X11 environment. Goals are: do as little work as possible to cope with little cpu resources - for example I'd like to record video in the native MJPEG I get out of the UVC devices encoding audio to MPEG3 Layer-2 (aka mp2) is ok since it let us save a lot of space (compared to raw pcm samples) and does use little cpu power I don't mind loosing some video frames here and there (UVC devices do that) as long as I can get audio and video streams syncronized not require user input to start the thing (a python script takes care of initialization, startup, shutdown, etc...) be able to open the resulting files for postprocessing without too much effort (ie, if mplayer or vlc can play it, it's fine) So far the only app I found that could be started from command line and record V4L2 video + ALSA audio is mencoder but I'm having some difficulties with it. It should be able to do that but I cannot record audio and video together - just one of the two. And if I use two different processes to record to two different files I have no means to get them in sync (audio is more or less always correct, but video framerate will vary over time and it seems to lack timestamps to correctly play it back to the correct time). Long story short, how do you record an unconverted MJPEG stream (from an UVC device) and an audio stream (from an ALSA device, possibly encoding to any standard format) using a command line tool, to a single file (MPEG or any other container), keeping audio and video in sync?

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  • Postfix spool on ext3 optimiziations in >=linux-2.6.34 days

    - by Luke404
    Given the very specific nature of the subject (we're not talking about mailboxes, just the spool; we're not talking about other filesystems, just ext3; and so on...) and the maturity of the softwares involved (linux kernel, ext3fs, postfix) I'd think there should be a more or less agreed on set of best practices to filesystem related tuning. I'm trying to get a roundup of them: data=journal became the default in recent kernels (somewhere around 2.6.30 IIRC) so we should be ok with that Wietse Venema says atime must be on, but Postfix documentation recommendsnoatime while talking about the Incoming Queue. Does that mean that postfix needs atime on just for some queue directories and will benefit from noatime on the others? can we use noatime if we just don't use ETRN? filesystem can be mounted nodev,noexec,nosuid - no* won't prevent you from setting attributes (postfix uses exec attr) they just won't have any effect (we don't run anything from the spool) the fsync() issue cited by Wietse and/or the chattr -S are probably linked to sync/async options of ext3fs but I do not understand them enough. Mouting the filesystem with async option is equivalent to chattr -R -S the whole fs? Seems like it will increase performance, but will that pose a risk of "loss of mail after a system crash" or is it really "safe on /var/spool/postfix" ? would you tune anything else on postfix-2.6.x to work better on ext3 or do you leave defaults everywhere? is there a "best" linux I/O scheduler for this kind of workload (namely CFQ or deadline?) or that's something that will vary too much based on hardware configuration? would you tune anything else in the filesystem or in the kernel? anything else? References: Postfix Performance here on SF Postfix documentation about the Incoming Queue Wietse Venema in Best file system on [email protected] here Postfix and ext3 on [email protected] here and there

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  • How to refresh open source software pkg manager on oldish OpenSolaris?

    - by Luke404
    I'm being presented with an OpenSolaris vps, actually a Solaris Container, which is based on SXCE snv_121 and is active since mid 2007: the good old Sun days, IIRC even before the Indiana stuff! For various reasons the system itself can't be rebuilt/upgraded but we can do whatever we want with the additional package manager on it. My Solaris skills and especially knowledge of the free package managers ecosystem is a bit rusty so I don't know what I can actually use while keeping the somewhat oldish base system. Currently there is pkg-get using some older Blastwave mirror, it has been used to install things such as Apache2, PHP, Python, Nagios. I would like to remove all the old rusty stuff and all of Blastwave, and start fresh with some newer package distribution. Can the current Blastwave system be used on that snv_121? Is there any better alternative still compatible with that system (eg. OpenCSW or anything else) ?

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  • Puppet: how to use data from a MySQL table in Puppet 3.0 templates?

    - by Luke404
    I have some data whose source-of-truth is in a MySQL database, size is expected to max out at the some-thousands-rows range (in a worst-case scenario) and I'd like to use puppet to configure files on some servers with that data (mostly iterating through those rows in a template). I'm currently using Puppet 3.0.x, and I cannot change the fact that MySQL will be the authoritative source for that data. Please note, data comes from external sources and not from puppet or from the managed nodes. What possible approaches are there? Which one would you recommend? Would External Node Classifiers be useful here? My "last resort" would be regularly dumping the table to a YAML file and reading that through Hiera to a Puppet template, or to directly dump the table in one or more pre-formatted text file(s) ready to be copied to the nodes. There is an unanswered question on SF about system users but the fundamental issue is probably similar to mine - he's trying to get data out of MySQL.

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  • DAS vs SAN storage for serving 2 to 4 nodes

    - by Luke404
    We currently have 4 Linux nodes with local storage, arranged in two active/passive pairs with storage mirrored using DRBD, running virtual machines (actually using Xen Hypervisor) for typical hosting workloads (mail, web, a couple VPS, etc.). We're approaching the (presumed) maximum IOPS of those servers, and we're planning to migrate to an external storage solution with two active nodes, with capacity for up to four active nodes. Since we're an all-Dell shop I've done some research and found the MD3200 / MD3200i products should be the ones we're looking for. We are pretty sure we won't be attaching more than 4 hosts on a single storage and I'm wondering if there is any clear advantage for one or the other. In theory I should be able to attach 4 SAS hosts to a single MD3200 (single links on a single controller MD3200, or dual redundant SAS links from each host to a dual-controller MD3200), or 4 iSCSI hosts to a single MD3200i (directly on its 4 GigE ports without any switch, again with dual links for the dual controller option). Both setups should let us implement live VM migration since all hosts can access all the LUNs at the same time, and also some shared filesystem like GFS2 or OCFS2. Also, both setups should allow full redundancy of the whole system (assuming dual controllers in the storage). One difference I can see is that the DAS solution is actually limited to 4 hosts while the iSCSI one should be able to grow to more hosts (adding two GigE switches to the mix). One point for the iSCSI solution is that it would allow us to start out with our current nodes and upgrade them at a later time (we can't add other SAS controllers, but they already have 4 GigE ports each). With the right (iSCSI|SAS) controllers I should be able to connect diskless nodes and boot them off the external storage which I think is a good thing (get rid of any local storage). On the other hand, I would have thought the SAS one to be cheaper but it seems like an MD3200 actually costs a little less than an MD3200i (?) (please note: I've used Dell gear in my examples since that's what we're looking for but I assume the same goes with other vendors) I would like to know if my assumptions above are correct, and if I'm missing any important difference between the two setups.

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  • How do I collect SNMP readings from intermittently-connected sites?

    - by Luke404
    I am collecting SNMP data on-site for a number of systems, currently using Cacti. These systems are spread on a number of sites that aren't always connected to internet, but I also need to centralize the data on a single system (datacenter housed server) and get graphs out of it. If I directly poll remote systems with a centralized Cacti I'd loose data when a site is not connected to internet. I should record data on-site (I have a server at each site and I can run whatever I want on it) and then 'sync' everything to the central system. One hack could be a cacti or directly an rrdtool on site and then periodically rsync RRD data to the central Cacti system, but that doesn't sound like a 'clean' solution: every RRD would have to be defined at both places and rsync scripts setup with the specific file names. Can you suggest a better solution? Cacti is not a requirement but I'd like to use something like that on the central system. On-site systems need only to collect data I don't need to graph it there or manage users rights to view data and stuff like that, users will only access the centralized system.

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  • Ubuntu: disable udev's persistent-net-generator.rules

    - by Luke404
    I'm using Ubuntu 12.04 LTS server edition and I am modifying /etc/udev/rules.d/70-persistent-net.rules to define my own mappings of ethernet interfaces to MAC addresses; that file is initially generated by rules in /lib/udev/rules.d/75-persistent-net-generator.rules at system installation time (or at the first boot, I actually don't know and it doesn't matter here). How can I be sure that my edited version will never ever be overwritten by anything? Removing the persistent-net-generator, as suggested on some websites, is not the Right Thing™ to do as told by comments in the file itself: it will be overwritten by any update of the udev package. I'm looking for a more formally correct way to disable it. Is it enough to just make sure that /etc/udev/rules.d/70-persistent-net.rules does exist? Maybe there are other events that could trigger its regeneration? (eg. adding or removing ethernet interfaces to the system?)

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  • does it still have any sense to directly drop mails that trigger RBLs?

    - by Luke404
    Once upon a time, using RBLs to drop mails was actually a good idea. These days seems it is no more possible for a reason or the other, so every one switched / is_switching to just use RBLs as another test in score based antispam solutions (read: SpamAssassin & friends). This gives good results, but neglects one of the benefits of RBLs, namely the ability to reject (supposed) spam before even receiving the message body. Is still there any RBL that makes sense to use that way, to hardly reject anything that fires a match in that list? If there are people doing it that way, do you ever get false positives due to the list?

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  • Get Safari to use different autocompletion on different URLs on same hostname

    - by Luke404
    I have a webserver publishing different services over the same SSL VirtualHost, the two most commonly used being PhpMyAdmin and Cacti. These (and others) use 'cookie' style authentication, asking user and password in an HTML form (thus not using HTTP Authentication). Being on the same hostname, the Safari browser didn't manage too well stored passwords: if I login to one app with user foo, and then go to app two it would propose me user foo and its password in the login form. Changing just the username to bar used to be sufficient to let Safari autocomplete the correct password in its form field. Annoying, but I could live with it - usernames are short and easy to remember when compared to the passwords we use. After the update to safari5 this seems to be no longer true: if I store in safari (actually user keychain on OSX) credentials for https://www.foobarbaz.com/app1 AND credentials for https://www.foobarbaz.com/app2 there seem to be no way for it to autocomplete both based on the url. Even editing the keychain to add the path (it will store only the hostname by default) does not help. Is there anything I can do to let it work the way I want while still keeping everything on one hostname? Modifying anything server side is of course possible, but I can't switch apps to HTTP Auth (and not every one will support it anyway) to use different 'realms'.

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  • What disk setup is needed / best practice for hypervisor-only servers?

    - by Luke404
    Planning to buy some servers to run an hypervisor (Citrix XenServer or VMware vSphere, still have to decide between the two) we'd like to boot off the local redundant SD card module offered by various vendors (eg. Dell, HP, etc...). The actual VMs will run from an existing iSCSI SAN (which, by the way, can't support booting the servers directly off the SAN). What are the reasons, if any, to choose completely diskless servers VS having some local storage? And what would be the guidelines to choose that local storage? (number of spindles, raid level, etc)

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  • When should NTPd broadcast/broadcastclient be used instead of client/server or peer modes?

    - by Luke404
    The NTP deamon if often used in its simplest mode, which is client/server: you specify one or more server directives in your ntp.conf and your clients will use those servers. In addition to that, when you run your own NTP servers, it is good practice to peer them together, so if one of them looses connectivity to its upstream servers, it will get time from its peers. But NTPd can also work with broadcast and/or multicast distribution of time data, with the documentation stating: broadcast and multicast modes are intended for configurations involving one or a few servers and a possibly very large client population The documentation also says elsewhere: It is possible and frequently useful to configure a host as both broadcast client and broadcast server. A number of hosts configured this way and sharing a common broadcast address will automatically organize themselves in an optimum configuration based on stratum and synchronization distance. I can see one obvious administrative benefit: you don't have to manually specify and update your list of NTP servers in the clients ntp.conf, so to me it looks tempting to use broadcast mode even for a small client population (say 5+ clients with 3~4 servers). I expect network traffic to be a little higher with broadcasts instead of client/server associations, but given the usual gigabit ethernet LAN the impact should be negligible unless you have a very very large number of hosts in the same broadcast domain. At the end of the day, when should broadcast mode be used or avoided? Are there pros and cons I haven't seen?

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  • How to batch convert video files on OSX for AppleTV2 / iPhone4?

    - by Luke404
    I'd like to have a solution to batch convert video files to a format suitable for the AppleTV2, iPad2, iPhone4, while at the same time preserving as much quality as possible; I want a single output file that will play on both devices and also good for consumption by other Mac software (eg. Aperture, iMovie, iTunes). Batch processing is a requirement since I'm gonna convert many many files from different sources (mainly lots of videos captured by compact digital cameras, cell phones, and so on). I'm looking into ffmpeg and MEncoder (both installed via MacPorts), but I can't seem to find a suitable preset for libx264 even if everyone out there is talking about them. A different approach involving different software would be ok too as long as I can script it somehow and run it on a whole directory full of files to be converted.

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  • Puppet: is it ok to "force" certname when you expect to shuffle nodes around?

    - by Luke404
    We all know (good example on SF) that Puppet hostname detection could be... fun. At our company (and I guess we're not alone at this) we usually pre-configure servers at our offices and test them before bringing the gear to a remote datacenter and rack them. Of course the reverse dns will change when doing that, even if we don't change the actual hostname of the system. We're slowly drafting our puppet setup and I'd like to be sure those moves won't create problems. My idea is to explicitly configure the desired full FQDN of the system as certname in puppet.conf at server provision time (before the very first puppet run). My process would look something like this: basic o.s. installation basic network configuration, enough to reach the internet and resolve dns install puppet and set up certname start puppet and let him manage the whole configuration test, fix problems in config (via puppet), re-test, and so on... manually stop puppet set up new network configuration for the datacenter network move the machine to DC turn it on puppet should automatically start and keep on doing its job The process is supported by detecting the environment in puppet's manifests (eg. based on subnet, like they do at Wikimedia) and modify configuration as needed (eg. resolv.conf contents appropriate for each network). Each node's certname will never change for the whole system life cycle. Is there any problem with this approach? Could it be improved?

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  • What URL scheme would be better for "nested" resources in a RESTful application?

    - by Luke404
    Let's say we want a RESTful web service to manage some logically nested resources, where each instance of resource 'B' is logically contained by an instance of resource 'A'. The first example that comes to mind, working as a sysadmin, is email accounts and their domains: [email protected] [email protected] [email protected] ... What URL scheme would you suggest? At first I'd try: /domain/[domainname] /domain/[domainname]/account/[accountname] is that in line with RESTful principles? or should I go with something like: /domain/[domainname] /account/[account@domainname]/ or anything else?

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  • python: how to design a container with elements that must reference their container

    - by Luke404
    (the title is admittedly not that great. Please forgive my English, this is the best I could think of) I'm writing a python script that will manage email domains and their accounts, and I'm also a newby at OOP design. My two (related?) issues are: the Domain class must do special work to add and remove accounts, like adding/removing them to the underlying implementation how to manage operations on accounts that must go through their container To solve the former issue I'd add a factory method to the Domain class that'll build an Account instance in that domain, and a 'remove' (anti-factory?) method to handle deletions. For the latter this seems to me "anti-oop" since what would logically be an operation on an Account (eg, change password) must always reference the containing Domain. Seems to me that I must add to the Account a reference back to the Domain and use that to get data (like the domain name) or call methods on the Domain class. Code example (element uses data from the container) that manages an underlying Vpopmail system: class Account: def __init__(self, name, password, domain): self.name = name self.password = password self.domain = domain def set_password(self, password): os.system('vpasswd %s@%s %s' % (self.name, self.domain.name, password) self.password = password class Domain: def __init__(self, domain_name): self.name = domain_name self.accounts = {} def create_account(self, name, password): os.system('vadduser %s@%s %s' % (name, self.name, password)) account = Account(name, password, self) self.accounts[name] = account def delete_account(self, name): os.system('vdeluser %s@%s' % (name, self.name)) del self.accounts[name] another option would be for Account.set_password to call a Domain method that would do the actual work - sounds equally ugly to me. Also note the duplication of data (account name also as dict key), it sounds logical (account names are "primary key" inside a domain) but accounts need to know their own name.

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