Set date on all your JPG photos from EXIF data

I don’t know if it’s a normal situation or it is one of that things that only happens to me: All my photos had lost their original timestamp. So all files have the same date (the date when files were copied from the old hard disk) and it’s a mess when you have gigs of photos from travels, family, events, animals, etc. without its original shoot date.

So I adapted this little script that reads EXIF data from JPGs recursively into folders and sets timestamp on the files accordingly. Easy!

All you need is the exiv2 tool (quickly available on your distro repos) and run this little script: (Remember to chmod it to a+x or 755).

Resize a mounted Linux partition

Today I’ve learnt that a Linux partition (which is mounted) can be grown “a la brava” (means “the hard way” in Catalan) directly modifying it through Fdisk and then resizing with resize2fs. That’s it….

With my own conservative way I’d boot the machine into Gparted (A very useful small distro that boots into Gparted directly), resize the partition (unmounted), and then reboot again.

The only condition is that the partition which has to be grown is the last one. If not… things get more complicated (or not, if the last partition is a swap one, which can be erased and recreated without problems). Other condition is that particion can only be grown (not shrink).

The process it’s easy:

  • First grow the disk physically (can be a VM disk, a new bigger disk just cloned, or simply a partition that does’nt fill the entire disk).
  • With Fdisk, remove the partition.
  • Without exiting Fdisk, create a new partition. Carefully note that the first sector match the previous first sector. The last sector can be the end of the disk i.e.
  • Verify/toggle Boot flag, must be activated.
  • Save and exit. Cross your fingers and reboot.
  • Once rebooted, grow the filesystem with resize2fs.


Bye backups… hi ZFS snapshots!

Today an entire folder disappeared from my Owncloud instance. It is an entire mystery why has disappeared. And I haven’t backups since owncloud data supposedly is synced between all client computers…

But, who wants backups when you have ZFS snapshots? I have all my private Owncloud data into a ZFS volume, and a cron job that do snapshots at midnight. Unlike Solaris, ZFS on Linux doesn’t have snapshotting natively so we have to use this set of pretty scripts: zfs-auto-snapshot

ZFS snapshots can be accessed like if they were a regular filesystem and they show you the files as it were just at the snapshot moment. The good thing is that the space occupied is *very* low (only stores changed data like it were an incremental backup).

So you only have to copy the missing data from the snapshot folder into the original place.

zfs list shows us all the datastores, mountpoints and snapshots:


We want to restore the latest snapshot from May 12th at 04:25am. First we have to ensure that snapshots are visible to us. We’ll set RomaniHD/Magatzem datastore to show snapshots. It will be located hidden on the datastore root (/datastore/.zfs)


Voilà, we have a virtual copy of our datastore of the last week:

Now we have to enter the desired folder (day) and copy the contents into the correct place.

In my case, I restored Owncloud data, so after copying the missing data I had to do a content refresh. First become www-data user and tell owncloud to refresh its entire data folder:


Streaming audio to two different targets (or networks)

It may sound strange, but one radio station (or somebody) may want to stream audio to two different networks. I had this special need in Boca Ràdio (a local Radio Station from Barcelona) because this station broadcasts through a provider and also broadcasts into (A community based, open and neutral network).

So, the box that transcode analog audio coming from the station’s sound mixer, it has to send it to:

  • Streaming provider in Shoutcast format
  • Localhost in Icecast format. In the same box there is an Icecast server listening to Guifi network clients. (Note that Icecast server may be running on another location).

I utilize this little transcoder: Darkice that reads configuration from /etc/darkice.cfg and sends analog audio coming from the Soundboard to the specified targets and in the specified format. It is available in Debian repo.

Configuring Icecast server is pretty straightforward but be sure that this items are properly configured:


Multiple internet WAN at home or office

It’s not uncommon to see on many offices that the Internet connection comes from several WAN connections (for redundancy, or whatever). Even on the more freak homes I’ve seen a multiwan setup (i.e., one wan from the ISP, other from a vpn, and other wan being stolen from the neighbors).

I know three methods for managing automatically more than one WAN connection. Best yet, automatically but meeting several rules (i.e.: youtube transit sent to wan1, bittorrent to wan2 and HTTPS transit to wan3).

Method 1: RouterOS PCC

Mikrotik routers can handle natively a multiwan setup through PCC (Per Connection Classifier). Packets must be marked with a routing mark and then the PCC chosses where to send them. Best references:

Method 2: OpenWRT MWAN3

MWAN3 is a package for OpenWRT that do the job and can be configured in a easy and visual way. So you need a powerful router fully compatible with OpenWRT and MWAN3. I have an ex-coworker that uses this stuff and wrote this excellent post:

Method 3: Linux

Method 1 and 2 requires a special router, but this method only requires a Linux Box with two or more ethernet cards. I’ve not tested it but it seems very interesting because it’s not hardware-dependant. In fact, that software is designed for, given more than one WAN connection, discard the first that gets disconnected (hence the title of the project).