Fstab change

bperegrine · n00b Joined: 23 Dec 2017 Posts: 37

Along with the other boot scripts (see https://forums.gentoo.org/viewtopic-t-1077378.html), I also want to include a script that tells fstab to list all my devices under /mnt/ with their UUID (rather than their device file).

Is there a command that allows to do this, or is there a line I can add to /etc/fstab that would do this ?

I read https://wiki.gentoo.org/wiki/Fstab and https://wiki.gentoo.org/wiki/Removable_media#UUIDs_and_labels
but neither has the answers I seek.

charles17 · Advocate Joined: 02 Mar 2008 Posts: 3664

Are you looking for something like this?

John R. Graham · Posted: Sat Mar 10, 2018 3:25 pm Post subject: Re: Fstab change

bperegrine · n00b Joined: 23 Dec 2017 Posts: 37

As I understand, fstab uses eudev, not udev.
So if I use udev instead, Autofs ( https://wiki.gentoo.org/wiki/AutoFS ) won't work any more ?
The only alternative I found for autofs are a few scripts for mdev (https://wiki.gentoo.org/wiki/Mdev/Automount_USB ) which I prefer not to use either.

If setting up the system to automatically show the uuid instead isn't possible, then are there any other ways on how I can customize things more ? I'm thinking of either adding labels automatically or changing the device names, or making symlinks.
See https://wiki.gentoo.org/wiki/Device_file
http://swift.siphos.be/linux_sea/hardwaremanagement.html#idm3548298893536

I assume I'll need to make udev rules, and so will need to make .rules files which need to be copied upon boot from my usb stick to /etc/udev/rules.d/ and which are then read by the machine.
See https://unix.stackexchange.com/questions/333697/etc-udev-rules-d-vs-lib-udev-rules-d-which-to-use-and-why
However, to make these rules I need to know how gentoo makes the standard names for the devices (ie does it detect the computer port on which the device is connected, or does it categorise the devices some other way (optical drives, ... ?)
Also, can someone list the contents of /lib/udev/rules.d/ here so they can be examined (I'm not working on gentoo yet) ?

In regards to the device names: if these can be altered easily, will I need to make changes on other programs too (like autofs ?) and if so, how do I do this ?

John R. Graham · Posted: Mon Mar 12, 2018 11:41 am Post subject:

Both udev and eudev run the rules identically by design. (I use eudev too.) eudev was forked from udev based on the concern that it would become impossible to build udev independent of systemd one day, not to significantly alter its behavior.

Zucca · Posted: Mon Mar 12, 2018 1:21 pm Post subject: Re: Fstab change

bperegrine · n00b Joined: 23 Dec 2017 Posts: 37

I've started to read up on how udev works (https://www.linux.com/news/udev-introduction-device-management-modern-linux-system ), but here are a few more questions that arose from that:

I read that a "cdrom" and "dvd" symlink is automatically created (https://wiki.gentoo.org/wiki/Device_file#Symlinks ); however /etc/udev/rules.d/ is empty, so which file specifies the creation of these symlinks ? and how do I change or remove these symlinks (the proper way) ?

---

I understand that it indeed looks at the computer port (see http://www.linuxfromscratch.org/lfs/view/6.3/chapter07/symlinks.html ; ata_id, scsi_id, ... ) and also attains additional data from the device (http://hintshop.ludvig.co.nz/show/persistent-names-usb-serial-devices/ ;Vendor ID Product ID) but how does it determine what's an optical drive (sr0) and what's a disk (https://wiki.gentoo.org/wiki/Removable_media ) ? (since both harddisks and optical drives can have the same computer port -ie IDE-cable, USB-cable, serial ata-cable) ?

---

If I make symlinks, then I assume I'll get more devices listed in /dev/ (which will make things more confusing). Is there a way to stop standard drivenames (not symlinks) from showing up (so hiding them, as deleting them will break the symlinks too I guess). Or can I just add a line in a .start file to delete the standard drivenames upon boot ?

krinn · Watchman Joined: 02 May 2003 Posts: 7470

bperegrine · n00b Joined: 23 Dec 2017 Posts: 37

At https://www.linux.com/news/udev-introduction-device-management-modern-linux-system I also noticed that serial ATA drives aren't differentiated from parallel ATA drives (both have their partitions given sdaX names).

Couldn't this be solved by making symlinks in dev/disk of all devices with "by-id's" beginning "scsi-SATA"+number 1-9
And if so, how ? Also, with what do the "by-id's" of the parallel ATA's start, and can these be renamed in a similar way ?

USB and firewire devices get different numbers in their names in between bootups due to operating in "by path" mode. Can this be changed to operate in "by-id" mode, without breaking anything ? If so, how ?

How are the USB and firewire drives called, regardless of the mode they use ? Are these names like "ttyUSB1", ... ? (see http://hintshop.ludvig.co.nz/show/persistent-names-usb-serial-devices/ ) If these are indeed the correct names, can't I just rename the symlinks (using a .start script) to USB+number ?

Next, since dev/sr0 and other sr's are located at /dev/disk/, there's actually no differentiation at all between "opticals" and "disks". So to do a differentiation, I was thinking to use a .start script to:
* move sr0 and other sr's (so all opticals) to a new folder called /dev/optical/
* update the /dev/cdrom and the /dev/dvd symlinks to point to the new location (/dev/optical/sr0)
* make the /dev/cdrom and the /dev/dvd symlinks invisisible in pcmanfm (so only the sr's in /dev/optical/ are visible in pcmanfm)

How do I do the above ?
Are additional changes needed (fstab changes); ie are there already mountpoints for these altered files, and if so, what are they, standardly ? Note that I'll use autoFS btw.

Update: I overlooked one other important issue: are all sdX's placed in /dev/disk/ standardly ? Or are they at /dev/ and is the /dev/disk/ folder empty ? In case the folder is empty, I could just add in a line to delete the folder instead, and just keep the srX's and sdX's in /dev/. It just needs to be coherent; ie if there's a /disk/ folder, there should also be a /optical/ folder, or otherwise, none should exist.

John R. Graham · Posted: Sun Mar 18, 2018 6:01 pm Post subject:

bperegrine · n00b Joined: 23 Dec 2017 Posts: 37

John R. Graham · Posted: Mon Mar 19, 2018 2:26 pm Post subject:

Okay that makes sense, but for mass storage, mounting by UUID solves the problem and is already supported. No need to reinvent that particular wheel. In my defense, that's what your original post was asking about. Did you get around to installing Gentoo yet? Do you intend to?

- John
_________________
I can confirm that I have received between 0 and 499 National Security Letters.

krinn · Watchman Joined: 02 May 2003 Posts: 7470

I could understand if your issue was like this user https://forums.gentoo.org/viewtopic-t-1072550.html but really, just for disk.
Just gives them a label and problem solve, you don't even need to figure out their UUID or any cryptic numbers, just look at /dev/disk/by-label to identify the wanted disk.

bperegrine · n00b Joined: 23 Dec 2017 Posts: 37

John R. Graham · Posted: Mon Mar 19, 2018 3:52 pm Post subject:

bperegrine · n00b Joined: 23 Dec 2017 Posts: 37

krinn · Watchman Joined: 02 May 2003 Posts: 7470

John R. Graham · Posted: Tue Mar 20, 2018 6:38 pm Post subject:

Besides, you know that you will need a running Gentoo system to build your custom Gentoo LiveCD, right? It should be obvious that you can't have the custom LiveCD available to get this running Gentoo system. So what do you intend to use? And what are you waiting for?

Anyway, krinn is right. I hardly ever touch the LiveCD except for occasional troubleshooting. In fact, I hardly ever install Gentoo because it's a rolling distribution. I'm currently typing on a Gentoo installation that was originally created in 2004:

bperegrine · n00b Joined: 23 Dec 2017 Posts: 37

krinn · Watchman Joined: 02 May 2003 Posts: 7470

then http://www.knopper.net/knoppix/index-en.html would better fit your needs, because linux is not a livecd

John R. Graham · Posted: Wed Mar 21, 2018 5:51 pm Post subject:

I somewhat agree with krinn. Let me point out that your planned approach is suboptimal in several ways:

LiveCDs are slow because CDs are slow. They also spin down frequently, which exacerbates their speed problem. Consider instead acquiring a USB hard drive and installing Gentoo there.
LiveCDs are not updatable, but only replaceable. On average, I install new software a few times per week, but you won't be able to. This is, in fact, one of Gentoo's strengths: the ease of adding new (and tweaking existing) software.
LiveCDs won't store your work. Since you need some re-writeable persistent storage anyway, why not make your vision simpler and install Gentoo on a removable hard drive?

- John
_________________
I can confirm that I have received between 0 and 499 National Security Letters.

bperegrine · n00b Joined: 23 Dec 2017 Posts: 37

Zucca · Posted: Thu Mar 22, 2018 12:54 pm Post subject:

You're losing all the benefits of Gentoo there.

bperegrine · n00b Joined: 23 Dec 2017 Posts: 37

The change has been finished, see
https://github.com/Sharrisii/TAZ_optional_usb_stick/blob/master/bootscripts/change_device_names.sh

In regards to the distro packages:
I got a list over at https://github.com/Sharrisii/TAZ/blob/master/TAZ_x86_v1_specs/package_list_TAZ.txt
The list isn't complete (no dependencies added), but I assume gentoo will add the dependencies automatically -using catalyst, or using the packages_install script here below- ?

I also made a "packages_install.sh script" ( https://github.com/Sharrisii/TAZ/blob/master/TAZ_x86_v1_specs/packages_install.sh ), the idea is to run this in between building the different catalyst stages (the idea is to start from scratch, so to make all 3 spec files, without a portage snapshot (as not needed when building from scratch).
The question I have however is: can such a packages_install.sh script be used at all ?

Another question is: does it need to install all packages (since I'll use many "boot options" ? By "boot options", I mean several squashfs archives in which the first one is the "core programs" squashfs, and additional boot options add more programs to this first squashfs (for instance boot option 2 adds program A and B to core programs, boot option 3 adds programs C and D (so NOT A + B + C + D).
If the packages_install script does not need to install all programs at once (after which the programs listed is pulled apart over several squashfs archives), do I need to install all packages for the core programs, and then immediately separate off the additional programs for the other boot options ? But how can these be separated off then if they can't be installed first ?
As said, I'm not going to do it myself, but it would help to know so that I can change the packages_install.sh script accordingly.

Re Tiny Core Linux: I know of that but I want an upstream distribution that actually has a large userbase and is updated often. I still want to update the live cd every year or so. Also, gentoo is closer to my preferences (tiny core is almost "unworkably" light, it still needs to be practical for everyday use.