Geekdom » Linux

Getting iPhones, iPads and other iDevices to Print

Rich — Tue, 17 Jan 2012 21:47:39 +0000

БогородицаiDevices like the iPhone and iPad have the ability to print to select “supported” printers. Basically, those printers are just broadcasting Apple’s bonjour service to which the iDevice detects natively.

However, those “supported” printers aren’t all that readily available and corporate environments being inundated with iDevices can’t rightly replace all of their printers.

With a standard CUPS server, the avahi-daemon, and a simple python script, this can be easily solved! Grab the script from https://github.com/tjfontaine/airprint-generate and run it against your installed CUPS printers.

Avahi/Bonjour is a protocol that does not cross subnets. If you have a need for this, which is a typical corporate need, check out http://www.grouplogic.com/Knowledge/PDFUpload/Info/WanBonjour_1.pdf

Recovering a Linux LVM due to lost information on a single member drive

Rich — Thu, 29 Dec 2011 22:48:36 +0000

ikoniIf an LVM partition table or data containing the LVM information on the physical volume is ever lost, there is a way back out

First, boot the system without the volume active. Get in to single user.
Second, identify the device in question. In this example, let’s say /dev/sdb1 has lost its LVM information.
Third, find the latest archive of the volume information in /etc/lvm/archive which contains the UUID that the system cannot find, but you are sure it is the disk that has had its volume information overwritten or lost (in this example, let’s say the file is MyLVMgroupA.vg)
Fourth, run pvcreate to restore the information:
pvcreate –uuid –restorefile /etc/lvm/archive/MyLVMgroupA.vg -ff /dev/sdb1
Fifth, reboot and all is good. Run an fsck just to be on the safe side!

Fedora 16 quirk

Rich — Thu, 29 Dec 2011 20:27:36 +0000

Fedora has become rather dramatic in its fast moving changes. Fedora of today is what RHEL will become, and the system as a whole will look entirely different. systemctl is one of the bigger changes, and going from Fedora 14 to Fedora 15 wasn’t that painl since most services transferred over with ease. However, going from Fedora 15 to Fedora 16, some key services got renamed.

It’s best to do a systemctl command prior to any upgrade to record what you had running previously. The NFS server, for example, is one such service that gets renamed and, thus, will not automatically start on an upgraded system due to the name change. To correct this:

systemctl enable nfs-server.service

Linux Logical Volumes

Rich — Thu, 29 Dec 2011 20:24:32 +0000

Fedora, as do other distros, freaks out when you add a physical drive to a system which had been previously part of another logical volume. This doesn’t happen often, but if it does, the symptom is when you run system-config-lvm and it exits unexpectedly with:

'NoneType' object is not iterable

The way to resolve this is to fdisk the new disk on the system, create a partition on it, and write that partition table back to the disk. This overwrites the previous LVM information.

Converting an ext3 file system to ext4

Rich — Sun, 14 Aug 2011 17:59:35 +0000

иконографияикони(adapted from https://ext4.wiki.kernel.org/index.php/Ext4_Howto#Converting_an_ext3_filesystem_to_ext4)

Assuming you have enabled ext3 on your filesystem via:

# tune2fs -j /dev/DEV

It is very easy to then enable the ext4 features on an existing ext3 filesystem, using the command:

# tune2fs -O extents,uninit_bg,dir_index /dev/DEV

WARNING: Once you run this command, the filesystem will no longer be mountable using the ext3 filesystem!

After running this command (specifically, after setting the uninit_bg parameter), you MUST run fsck to fix up some on-disk structures that tune2fs has modified:

# e2fsck -fDC0 /dev/DEV

Be sure to update your /etc/fstab accordingly! And, if you do perform this update on an ext3 root file system, BE AWARE that you may have to jump through some hoops to get this work work. Many modern distributions boot off of a ram disk, and it is likely that ext4 is not in that ram disk. You will have to rebuild your ramdisk in order to boot your system.