Can a (second) hard disc consist of only 1 extended/logical partition? Or is at least one primary necessary? - Hardware

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Thread: Can a (second) hard disc consist of only 1 extended/logical partition? Or is at least one primary necessary?

  1. Can a (second) hard disc consist of only 1 extended/logical partition? Or is at least one primary necessary?

    Assume I have a second hard disc in my system.
    Can I put only one extended/logical partiton on it?

    or is at least one primary partition per hard disc necessary?

    J.


  2. Re: Can a (second) hard disc consist of only 1 extended/logical partition? Or is at least one primary necessary?

    Jason Stacy wrote:

    > Assume I have a second hard disc in my system.
    > Can I put only one extended/logical partiton on it?


    Yes, you can. In fact, if GNU/Linux is your only operating system, you
    could even do that on your system disk.

    The Linux kernel doesn't care whether it lives in a partition that's either
    primary or logical. That's just legacy stuff from the days of DOS, and
    both OS/2 and Windows still require primary partitions to exist.

    The DOS-based versions of Windows needed to be installed in an active and
    primary partition starting within the first 32 MB of the disk volume, on
    the first disk found by the BIOS. For NT-based systems, only the
    bootloader and a few files need to exist in such a primary partition, while
    the rest can be installed in a logical partition in an extended partition
    container, or even on another disk.

    UNIX-style operating systems like GNU/Linux have traditionally not cared
    about the partition being primary or logical.

    > or is at least one primary partition per hard disc necessary?


    Negative, although you may be surprised to hear that even an extended
    partition container is in fact a primary partition. The definition
    "primary partition" simply means that it's a partition with its entry in
    the partition table in the disk's master boot record. Logical partitions
    have their partition entry in the extended partition container.

    The whole thing came to be when hard disks started becoming available with
    capacities that exceeded 32 MB, e.g. the 40 and 60 MB hard disk in the IBM
    PS/2 series. The FAT filesystem under DOS 3.xx could only handle 32 MB, so
    a second partition was needed to take advantage of the extra space, but DOS
    (and later on the DOS-based Windows versions) could only handle one primary
    partition per disk, so the concept of an extended partition container was
    born, i.e. a primary partition that holds other, logical partitions,
    together with a partition table for them.

    In addition, it was a solution for the fact that systems using the
    legacy /x86/ BIOS can only handle four primary partitions, while more
    partitions may be needed. However, systems with an EFI BIOS - this is
    still rare in the /x86/ world - can handle as much as 128 primary
    partitions per disk.

    Technically, you can even do without a partition at all for GNU/Linux and
    simply format the available diskspace, but this is not something I would
    advise. Especially for UNIX systems, I am much rather a proponent of using
    different partitions for specified branches of the filesystem hierarchy
    tree. For instance, you best split off */var* and */home* from the root
    filesystem, and have */tmp* exist on a /tmpfs./

    I personally split off way more than that on my own systems and on our
    network's servers, but at least those(/three) two are the ones containing
    variable files and are thus best separated from the static data. Splitting
    certain subtrees off from the root filesystem also allows you to mount them
    with different options - e.g. read-only - or to even have them housing a
    different filesystem type.

    Either way and to summarize, if you're running an NT-based Windows on your
    system - e.g. XP or Vista - then only the partition containing the Windows
    bootloader needs to be primary (and marked active), regardless of whether
    you install the main Windows system in it or in another partition.
    Everything else can be a logical partition in an extended partition
    container. If on the other hand your system _only_ runs GNU/Linux, then
    none of it matters.

    The most common set-up for dual-booting systems with Windows and GNU/Linux
    is to have an active primary partition on the first disk in which you
    install Windows, and to use logical partitions on all disks from there on
    for both the Windows data partitions and the GNU/Linux partitions.

    --
    Aragorn
    (registered GNU/Linux user #223157)

  3. Re: Can a (second) hard disc consist of only 1 extended/logical partition? Or is at least one primary necessary?

    Jason Stacy wrote:

    > Assume I have a second hard disc in my system.
    > Can I put only one extended/logical partiton on it?
    >
    > or is at least one primary partition per hard disc necessary?


    ------------------------------------------------------------
    NOTE: FollowUp-To ignored. If your post was on-topic to each of the
    newsgroups to which you cross-posted then the continued discussion is
    also on-topic. Don't be rude by yanking away a discussion from visitors
    in the other newsgroups to what you like as your "home" group (since you
    can see the replies there, anyway, because you cross-posted). If you
    don't want to show the discussion there then don't cross-post there.
    ------------------------------------------------------------

    You must meet all of the following conditions:

    x = 1 (or 0) to 4 primary partitions (*)
    y = 0 or 1 extended partition
    x + y = 1 to 4 partitions

    Or, put another way:

    - Primary partitions:
    1 minimum (or 0 minimum) (*)
    4 maximum
    - Extended partitions:
    0 minimum
    1 maximum
    - Total partition count:
    1 minimum
    4 maximum

    (*) The 1 minimum primary partition applies to the first hard disk that
    is detectable by the BIOS.

    After the BIOS completes its POST (power-on self test), it loads the
    bootstrap program from the MBR (master boot record) from the first hard
    disk that it finds. The first sector of the hard disk is the MBR and is
    not allocated to any partition (as well as the remaining 62 sectors of
    the first track on the hard since tracks are assigned in 63-sector
    increments). The first 446 bytes are the bootstrap program. So the
    BIOS needs to load the bootstrap program into memory and pass control to
    it. The BIOS *only* looks for the bootstrap program from the MBR on the
    *first* hard disk detected.

    The standard bootstrap program reads the partition table (also in the
    MBR on the first hard disk). It looks for which partition is marked
    "active". Only primary partitions can be marked with a status of active
    and only one primary partition can be active at a time. The bootstrap
    program uses the partition table information to figure out where the
    partitions reside. Partition entries in the MBR can only define areas
    within the same hard disk. So the bootstrap program finds which primary
    partition is active and that partition must be on that hard disk. The
    MBR bootstrap program then loads the OS boot loader starting in the
    first sector of the active (primary) partition.

    This is the old BIOS scheme of how to boot a system. The BIOS loads the
    bootstrap program in the MBR from the first detected hard disk which
    reads the partition tables in the same MBR to then load the OS boot
    loader in the primary partition marked as active and which can only
    reside on the same hard disk since partition tables only delineate areas
    on that hard disk. Other software-based schemes have evolved that
    replace the OS boot loader in the first sector of the partition (that
    the MBR bootstrap loaded), the OS loader lets you specify from where to
    load the actual OS (like Microsoft's dual-boot), or they replace the MBR
    bootstrap program to eliminate the restriction that the boot partition
    is primary or even has to be on the same hard disk. So with a multiboot
    manager replacement for the bootstrap program, you can boot to any type
    of partition (primary or to a logical drive under an extended partition)
    which can be on any hard disk. Some BIOSes have been extended to
    perform the same functionality as the software multiboot managers to
    allow booting from any partition or logical drive on any hard disk.

    So it depends on the capabilities of your BIOS and/or bootstrap program
    as to how you can setup your partitions. For the old BIOS scheme using
    a standard bootstrap program, you'll need a minimum of 1 primary
    partition on the first BIOS-detectable hard disk. For newer extended
    BIOS schemes or when replacing the MBR bootstrap program, your limits
    are still based on what that extended BIOS or multiboot software can do
    but those exceed what you could do under the old scheme.

    RTFM

  4. Re: Can a (second) hard disc consist of only 1 extended/logical partition? Or is at least one primary necessary?

    VanguardLH wrote:

    > ------------------------------------------------------------
    > NOTE: FollowUp-To ignored. If your post was on-topic to each of the
    > newsgroups to which you cross-posted then the continued discussion is
    > also on-topic. Don't be rude by yanking away a discussion from
    > visitors in the other newsgroups to what you like as your "home"
    > group (since you can see the replies there, anyway, because you
    > cross-posted). If you don't want to show the discussion there then
    > don't cross-post there.
    > ------------------------------------------------------------


    How exactly does Follow-Up work? I looked at OP's headers and noticed
    Follow-Up. Why it used? How? I wasn't able to tell which news reader was
    used, either.

    Is it ever appropriate to use Follow-Up? How does one undo Follow-Up
    (which I presume you did)?



  5. Re: Can a (second) hard disc consist of only 1 extended/logical partition? Or is at least one primary necessary?

    Daave wrote:

    > VanguardLH wrote:
    >
    >> ------------------------------------------------------------
    >> NOTE: FollowUp-To ignored. If your post was on-topic to each of the
    >> newsgroups to which you cross-posted then the continued discussion is
    >> also on-topic. Don't be rude by yanking away a discussion from
    >> visitors in the other newsgroups to what you like as your "home"
    >> group (since you can see the replies there, anyway, because you
    >> cross-posted). If you don't want to show the discussion there then
    >> don't cross-post there.
    >> ------------------------------------------------------------

    >
    > How exactly does Follow-Up work? I looked at OP's headers and noticed
    > Follow-Up. Why it used? How? I wasn't able to tell which news reader was
    > used, either.


    If your newsreader doesn't alert you (and Outlook Express will not) then
    you need to notice the Newsgroups header of the article that you read
    versus the Newsgroups header in your reply. If they are different, a
    FollowUp-To header was probably used. This means when you reply, the
    poster is deliberately trying to redirect your reply to only one or some
    of the original newsgroups or even to a completely different newsgroup
    (spammers and malcontents love to try using FollowUp-To to redirect
    negative replies to, say, alt.test). If you look at the headers of a
    post and see a FollowUp-To, that post's author is trying to send replies
    somewhere not expected. Usenet etiquette dictates that if you change
    the Newsgroups header in your reply or you use the FollowUp-To header
    that you announce it at the start of your reply so respondents know what
    you did or are trying to do.

    In Outlook Express and while composing a post, use the View -> All
    Headers menu to show the FollowUp-To field. The FollowUp-To header is
    usually not included in the overview headers when your newsreader polls
    for a list of new messages on the NNTP server, so you cannot define a
    rule that will delete or colorize any that use the FollowUp-To header.
    However, in some newsreaders, you can still define a filter or score
    value to posts when you yank them in full because all headers will then
    be included. So my program can color them in the message list to notify
    me that the poster used the FollowUp-To header when I pull their message
    in full. I can also configure which headers, when present, will appear
    in the header pane above the preview window showing the body of their
    post. So if I add FollowUp-To as a header to display (and make it
    bolded and colored) then I also see it there. OE can't do any of that.
    At best, you can try to use the NewsProxy (aka nFilter) on your host
    through which you yank newsgroups and have it drop or tag posts that use
    the FollowUp-To header and use a rule in OE to look for the tag (if you
    chose not to drop the post) but, again, that would only work if the NNTP
    server to which you connect happens to include the FollowUp-To header in
    the set of overview headers, and few NNTP server include it. OE can't
    test on but a few headers, and FollowUp-To is not one of them so using
    NewsProxy to add a tag is how you would get OE to exercise a rule on
    them. You'd think that if you set OE to sync by yanking the whole
    message instead of just headers that you would then have the tag added
    by NewsProxy but OE doesn't update the headers that it already got from
    a prior message poll that included the Subject, From, and other headers
    for that post.

    Because of nym-shifters, mail2news cowards, kooks, children (regardless
    of age), and especially due to spam, I had to eventually give up using
    OE (even with NewsProxy). I had trialed several newsreaders in several
    tests over the last few years but they all had defects that I wouldn't
    tolerate or would not meet my one critical criteria that I can sort
    watched threads to the top of the message list. Obviously if I mark
    them to be watched then I really do want to watch them without having to
    scroll through dozens or hundreds of other posts to get to them, or
    having to use some convoluted workaround. I had include 40tude Dialog
    in those prior trials but canned it because of this deficiency. Decent
    multi-column sorting is missing in many newsreaders. It was only
    because I gave Dialog a lot more of a chance and spent 4 nights working
    on scripts to get it to work at about 98% of what I demanded that I then
    chose to stick with it.

    > Is it ever appropriate to use Follow-Up? How does one undo Follow-Up
    > (which I presume you did)?


    No, I *ignored* the attempt to use FollowUp-To for a post sent to 4
    groups that tried to send replies to just 1 of them. That means I made
    the Newsgroups header in my post the same as the Newsgroups header in
    the original poster's message; i.e., my replies went to the same groups
    that the poster decided to submit their message. The original poster
    claims those groups are all related to his topic (and I only remove them
    if it is obvious that they are not) but is then rude in yanking away the
    replies so the discussion disappears to a different group than where the
    user read it. Below is my rant on the very poor usage of FollowUp-To
    that is rampant because users are recommended to use it on some sites
    but don't think it through using some logic.


    --- Rant on inappropriate use of the FollowUp-To header ---

    Don't use the FollowUp-To header. Posting to, say, 3 newsgroups but
    moving replies to just 1 of them or to a completely different one means
    you disconnect the visitors of those other 2 (or 3) newsgroups from the
    rest of the discussion. If a newsgroup is appropriate for your post
    then it is also appropriate for the replies. Or, converserly, if the
    continued discussion of your post is not appropriate in all the
    newsgroups to which you cross-posted then you should not have posted to
    those other newsgroups in the first place. You are using the
    FollowUp-To header to move replies to YOUR "home" newsgroup but which
    the users of the other newsgroups may not visit. After all, if you
    cross-post and include your "home" newsgroup then you'll see all those
    replies in your home newsgroup and meanwhile all the other users can
    still see the replies in their newsgroup where you decided to also
    publish your post.

    In http://www.faqs.org/faqs/usenet/primer/part1/, it says, "For a
    cross-post, you may want to set the Followup-To: header line to the most
    suitable group for the rest of the discussion". Read another way, that
    means you disconnect the discussion from all the visitors of the other
    newsgroups to which you decided to publish your post. Why did you
    publish to those other newsgroups if you are going to yank the
    discussion away from those users and perhaps even from the respondents
    you were attempting to elicit? It is exasperating to post a reply and
    never see it in the newsgroup where you read the original post. If your
    post was appropriate for all the groups to which you cross-posted then
    why wouldn't those same groups be appropriate for the replies? To yank
    away the discussion to your "home" group is rude since that is probably
    not the "home" group for your respondents. You wanted replies which may
    require further replies but now your respondents no longer see the
    thread in the newsgroup that they visit to where you published your
    post. Also, the respondents may not know if their reply is appropriate
    in the "home" group that you happen to choose. In general, malcontents
    and spammers use the FollowUp-To header to hide negative replies to
    their flame or spam posts, often sending the replies off to a *.test
    newsgroup.

    There are some cases where FollowUp-To should be used. For example, say
    a newsgroup is supposed to only get used for citing the content of a
    spam e-mail. Discussions about that spam are not supposed to be
    published in that citing newsgroup. Just the exhibits are published
    there. If someone wants to discuss that particular spam, their replies
    should go into a different newsgroup meant for those discussions. I
    believe that is how some of the NANAE newsgroups operate but the
    principle may apply elsewhere but it is rare few newsgroups where
    FollowUp-To is appropriate. For the vast majority of newsgroups,
    FollowUp-To is *not* appropriate. If you do not want continue the
    discussion in the other newsgroups then don't cross-post over there (and
    then use FollowUp-To to yank away the continued discussion). If the
    discussion is not appropriate in those other newsgroups then it seems
    you have nominated your post to be spam.

    If you do use the FollowUp-To header, you are expected per netiquette to
    alert the readers of your post that you used that header. Be polite and
    add a note (at the start of your post) saying that you used the header
    (ex., "WARNING: FollowUp-To was used and points to ". You
    might also want to explain why any further discussion in the other
    newsgroups is inappropriate despite your rudeness in posting to those
    other newsgroups. Many times respondents wonder where their reply post
    went because they expect to see it in the group they visited and where
    they read your post. Not all NNTP clients alert the user that the
    poster used the FollowUp-To header. Think about it: you post to
    multiple newsgroups but yank the replies to a different newsgroup than
    where your respondents visited, then you need more help and reply to
    those replies but which are now only in your "home" newsgroup, but the
    respondents won't see their posts nor will they see your replies to them
    asking for more help. FollowUp-To is not required when you cross-post
    since your "home" newsgroup should be one those that were specified in
    the list of newsgroups. You'll watch the discussion in your home
    newsgroup and the respondents or lurkers can watch that same discussion
    in their own newsgroup. If you don't want replies to show up in all the
    newsgroups to which you cross-posted then don't cross-post over there in
    the first place!

    When crossposting, there are not multiple copies of your post that
    wastes bandwidth for each to get them propagated to other NNTP servers
    and there aren't multiple copies of your post consuming disk space. A
    single copy gets sent to the other NNTP servers and a single copy
    resides on each NNTP server with pointers to it to make it show up in
    multiple newsgroups. You aren't saving bandwidth or disk space by
    redirecting replies for a cross-posted message to a single newsgroup.
    You are just being rude to the visitors of the other newsgroups to which
    you cross-posted but tried to yank away the discussion.

    --- End of rant ---

    If you choose to continue this subthread which has become off-topic to
    these newsgroups, I'll probably use FollowUp-To myself - but with notice
    - to move it to news.software.readers where it is on-topic. I doubt the
    hardware folks really want to debate over the pros and cons of various
    newsreaders or over Usenet etiquette.

  6. Re: Can a (second) hard disc consist of only 1 extended/logical partition? Or is at least one primary necessary?

    VanguardLH wrote:



    > If you choose to continue this subthread which has become off-topic to
    > these newsgroups, I'll probably use FollowUp-To myself - but with
    > notice - to move it to news.software.readers where it is on-topic. I
    > doubt the hardware folks really want to debate over the pros and cons
    > of various newsreaders or over Usenet etiquette.


    That was very thorough. Thanks for the post!



  7. Re: Can a (second) hard disc consist of only 1 extended/logicalpartition? Or is at least one primary necessary?

    On Sun, 20 Apr 2008 03:31:41 +0200, Aragorn wrote:

    > Technically, you can even do without a partition at all for GNU/Linux
    > and simply format the available diskspace, but this is not something I
    > would advise. Especially for UNIX systems, I am much rather a proponent
    > of using different partitions for specified branches of the filesystem
    > hierarchy tree. For instance, you best split off */var* and */home*
    > from the root filesystem, and have */tmp* exist on a /tmpfs./


    The style I like is to have one partition for /boot and the rest of the
    disk in a single partition which is allocated to LVM. LVM volumes can
    then be created for /home, /usr, /var, etc. This permits new volumes to
    be created, or existing ones resized, w/o having to worry about the
    concept of "disk layout".

    This is also easily RAIDed by md.

    Adding a non-boot disk, I create a single partition and allocate that to
    LVM. In theory, this can be done using the entire disk (as opposed to a
    single partition consuming the entire disk). But someone not expecting
    this can be easily confused if he or she were to try to look at the
    disk's partition table, so I avoid that choice in following the principle
    of least astonishment.

    - Andrew

  8. Re: Can a (second) hard disc consist of only 1 extended/logical partition? Or is at least one primary necessary?

    (Follow-up set to comp.sys.ibm.pc.hardware.storage)
    On 2008-04-20, Aragorn wrote:

    > The Linux kernel doesn't care whether it lives in a partition that's either
    > primary or logical. That's just legacy stuff from the days of DOS, and
    > both OS/2 and Windows still require primary partitions to exist.


    OS/2 only needs a primary partition for its Boot Manager. If you're not
    using the OS/2 Boot Manager you don't need a primary partition.

    --

    John (john@os2.dhs.org)

  9. Re: Can a (second) hard disc consist of only 1 extended/logical partition? Or is at least one primary necessary?

    ["Followup-To:" header set to comp.os.linux.hardware.]
    Andrew Gideon :
    > On Sun, 20 Apr 2008 03:31:41 +0200, Aragorn wrote:
    > >
    > > hierarchy tree. For instance, you best split off */var* and */home*
    > > from the root filesystem, and have */tmp* exist on a /tmpfs./

    >
    > The style I like is to have one partition for /boot


    Why? What's that get you if /sbin is unreadable?

    > and the rest of the
    > disk in a single partition which is allocated to LVM. LVM volumes can
    > then be created for /home, /usr, /var, etc. This permits new volumes to
    > be created, or existing ones resized, w/o having to worry about the
    > concept of "disk layout".


    Or, have a 40 Gb disk, install (a la Aragorn) $OS, add a ca. 3 Gb
    /scratch, and I've 26 Gb left to portion out whenever I wish. What
    does lvm gain you in this situation but an added level of complexity?

    [Sorry for the rant ...]

    We've already the distros throwing their ideas of "simpler" at us, as
    in UUIDs in /etc/fstab (b*st*rds!), and the *obvious* need to migrate
    from a perfectly workable /dev/hd* /dev/sd* /dev/sr* to
    /dev/_everything's_an_s_something.

    Installers have improved greatly, don't get me wrong, and I'm very
    grateful, but these sorts of changes ought to be user-selectable in
    NON-expert mode installs. Sweeping changes demand strong warnings!

    I helped a guy install etch on his sandbox yesterday. It was already
    running Sidux fine. etch (non-expert) install insisted I install
    grub. I told it /dev/hdb, where we were installing etch.

    On reboot, Sidux' (all on hda) grub couldn't find ptn 5. Ripping
    UUIDs out of Sidux menu.list and fstab and converting it back to /dev/hd*
    fixed it.

    Why did we have to go there? For the convenience of a bunch of dolts
    who can't find their usb keys when they plug them in? Why are we
    turning fstab and menu.lst into non-human-usable registries?

    fdisk /dev/hda
    Command (m for help): m
    Command action
    a toggle a bootable flag
    b edit bsd disklabel
    c toggle the dos compatibility flag
    ....
    U Select UUID addressable partitions
    ....

    or something. :-|

    Sorry about that b*! crack, but I think this is going the wrong way.


    --
    Any technology distinguishable from magic is insufficiently advanced.
    (*) http://blinkynet.net/comp/uip5.html Linux Counter #80292
    - - http://www.faqs.org/rfcs/rfc1855.html Please, don't Cc: me.

  10. Re: Can a (second) hard disc consist of only 1 extended/logical partition? Or is at least one primary necessary?

    In comp.os.linux.hardware, s. keeling wrote:

    > ["Followup-To:" header set to comp.os.linux.hardware.]
    > Andrew Gideon :
    >> On Sun, 20 Apr 2008 03:31:41 +0200, Aragorn wrote:
    >> >
    >> > hierarchy tree. For instance, you best split off */var* and */home*
    >> > from the root filesystem, and have */tmp* exist on a /tmpfs./

    >>
    >> The style I like is to have one partition for /boot

    >
    > Why? What's that get you if /sbin is unreadable?


    Why would you think that the only dependancy is on the readability of /sbin?

    A separate /boot partition
    - can be used with older machines where there is a BIOS limit to the
    location of the OS
    - can be mounted as read/only while the rest of the filesystem tree is r/w
    - can be backed up to a duplicate partition for recovery (alternate boot)
    purposes
    - can be stored as an ext2 (or minix, or vfat or ...) filesystem while the
    rest of the filesystem tree is some other fs (like ext3 or reiserfs)

    [snip]
    --
    Lew Pitcher

    Master Codewright & JOAT-in-training | Registered Linux User #112576
    http://pitcher.digitalfreehold.ca/ | GPG public key available by request
    ---------- Slackware - Because I know what I'm doing. ------



  11. Re: Can a (second) hard disc consist of only 1 extended/logicalpartition? Or is at least one primary necessary?

    On Mon, 21 Apr 2008, Lew Pitcher wrote:

    > In comp.os.linux.hardware, s. keeling wrote:
    >
    >> ["Followup-To:" header set to comp.os.linux.hardware.]
    >> Andrew Gideon :
    >>> On Sun, 20 Apr 2008 03:31:41 +0200, Aragorn wrote:
    >>>>
    >>>> hierarchy tree. For instance, you best split off */var* and */home*
    >>>> from the root filesystem, and have */tmp* exist on a /tmpfs./
    >>>
    >>> The style I like is to have one partition for /boot

    >>
    >> Why? What's that get you if /sbin is unreadable?

    >
    > Why would you think that the only dependancy is on the readability of /sbin?
    >
    > A separate /boot partition
    > - can be used with older machines where there is a BIOS limit to the
    > location of the OS
    > - can be mounted as read/only while the rest of the filesystem tree is r/w
    > - can be backed up to a duplicate partition for recovery (alternate boot)
    > purposes
    > - can be stored as an ext2 (or minix, or vfat or ...) filesystem while the
    > rest of the filesystem tree is some other fs (like ext3 or reiserfs)
    >

    I don't even mount /boot unless I have to make changes to it. I suppose
    you'll now give me a good reason why that's bad, but by definition /boot
    is only needed at boot time, and once you set up the bootloader so it
    knows where the actual kernel is, I can't see any reason why it needs
    to be mounted unless you are actually making changes to it.

    Michael


  12. Re: Can a (second) hard disc consist of only 1 extended/logicalpartition? Or is at least one primary necessary?

    On Tue, 22 Apr 2008 05:04:07 +0200, s. keeling wrote:


    >> The style I like is to have one partition for /boot

    >
    > Why? What's that get you if /sbin is unreadable?


    This isn't to make /sbin's content available; that's what RAID is for.
    This is to make the content of /boot available to GRUB. As far as I know
    - and please let me know if I'm out of date on this - GRUB doesn't
    "speak" LVM.


    [...]
    > Or, have a 40 Gb disk, install (a la Aragorn) $OS, add a ca. 3 Gb
    > /scratch, and I've 26 Gb left to portion out whenever I wish. What does
    > lvm gain you in this situation but an added level of complexity?


    A layer of indirection so that, when you "portion out whenever you wish",
    you don't need to worry that you've the necessary contiguous blocks.

    >
    > [Sorry for the rant ...]


    Yeah, what's that about? Did LVM kick you as a child or something
    ?

    - Andrew

  13. Re: Can a (second) hard disc consist of only 1 extended/logical partition? Or is at least one primary necessary?

    In comp.os.linux.hardware, Michael Black wrote:

    > On Mon, 21 Apr 2008, Lew Pitcher wrote:
    >
    >> In comp.os.linux.hardware, s. keeling wrote:
    >>
    >>> ["Followup-To:" header set to comp.os.linux.hardware.]
    >>> Andrew Gideon :
    >>>> On Sun, 20 Apr 2008 03:31:41 +0200, Aragorn wrote:
    >>>>>
    >>>>> hierarchy tree. For instance, you best split off */var* and */home*
    >>>>> from the root filesystem, and have */tmp* exist on a /tmpfs./
    >>>>
    >>>> The style I like is to have one partition for /boot
    >>>
    >>> Why? What's that get you if /sbin is unreadable?

    >>
    >> Why would you think that the only dependancy is on the readability of
    >> /sbin?
    >>
    >> A separate /boot partition
    >> - can be used with older machines where there is a BIOS limit to the
    >> location of the OS
    >> - can be mounted as read/only while the rest of the filesystem tree is
    >> r/w - can be backed up to a duplicate partition for recovery (alternate
    >> boot)
    >> purposes
    >> - can be stored as an ext2 (or minix, or vfat or ...) filesystem while
    >> the
    >> rest of the filesystem tree is some other fs (like ext3 or reiserfs)
    >>

    > I don't even mount /boot unless I have to make changes to it. I suppose
    > you'll now give me a good reason why that's bad,


    No, I won't. To me, that's a perfectly acceptable step to take to secure
    your system.

    > but by definition /boot
    > is only needed at boot time, and once you set up the bootloader so it
    > knows where the actual kernel is, I can't see any reason why it needs
    > to be mounted unless you are actually making changes to it.
    >
    > Michael


    --
    Lew Pitcher

    Master Codewright & JOAT-in-training | Registered Linux User #112576
    http://pitcher.digitalfreehold.ca/ | GPG public key available by request
    ---------- Slackware - Because I know what I'm doing. ------



  14. Re: Can a (second) hard disc consist of only 1 extended/logical partition? Or is at least one primary necessary?

    Andrew Gideon staggered into the Black Sun and said:
    > On Tue, 22 Apr 2008 05:04:07 +0200, s. keeling wrote:
    >>> The style I like is to have one partition for /boot

    >> Why? What's that get you if /sbin is unreadable?

    > This isn't to make /sbin's content available; that's what RAID is for.
    > This is to make the content of /boot available to GRUB. As far as I
    > know - and please let me know if I'm out of date on this - GRUB
    > doesn't "speak" LVM.


    It's not so much that GRUB *can't* understand LVM, but that LVM is
    complex enough that it'd be a complete and total PITA to implement an
    LVM reader in real-mode x86 code. And whatever they came up with would
    probably be too big to fit in the slack space between the MBR and the
    start of the first partition. It'd probably be doable if the VG
    containing the LV where /boot was was guaranteed to be composed of only
    PVs that are BIOS-addressable. The whole point of LVM is to remove
    those restrictions on where you can put LVs.

    >> What does lvm gain you in this situation but an added level of
    >> complexity?

    > A layer of indirection so that, when you "portion out whenever you
    > wish", you don't need to worry that you've the necessary contiguous
    > blocks.


    "It's a hell of a lot easier to resize an LV than it is to resize a
    partition" in other words. If you have your / on an LV, you can hook up
    a new disk and *move your / to that disk while the system is running*,
    which is a pretty cool thing to be able to do.

    >> [Sorry for the rant ...]

    > Yeah, what's that about? Did LVM kick you as a child or something
    >?


    LVM is more complicated, and nothing but Linux can understand LVM right
    now. This makes it a bad idea, IMHO, to use LVM unless the box is only
    running Linux, or if the other OS(es) will never need to access the
    stuff on the LVs.

    --
    Really, I'm not out to destroy Microsoft. That will just be a
    completely unintentional side effect. --Linus Torvalds
    My blog and resume: http://crow202.dyndns.org:8080/wordpress/
    Matt G|There is no Darkness in Eternity/But only Light too dim for us to see

  15. Re: Can a (second) hard disc consist of only 1 extended/logicalpartition? Or is at least one primary necessary?

    On Tue, 22 Apr 2008 17:47:07 +0000, Dances With Crows wrote:

    [...]

    > It's not so much that GRUB *can't* understand LVM, but that LVM is
    > complex enough that it'd be a complete and total PITA to implement an
    > LVM reader in real-mode x86 code.


    I didn't write "can't"; I wrote "doesn't". Please don't misunderstand
    me; what I wrote wasn't a complaint. Given the number of file systems
    "out there", it's not unreasonable for GRUB to require /boot be in some
    very limited set of file systems even if the rest of the file systems are
    from the wider set of what's available.

    [...]

    >> A layer of indirection so that, when you "portion out whenever you
    >> wish", you don't need to worry that you've the necessary contiguous
    >> blocks.

    >
    > "It's a hell of a lot easier to resize an LV than it is to resize a
    > partition" in other words.


    True, but the reason is that level of indirection. I think it worthy to
    mention that frequently, but I'm one of those "no problem cannot be
    solved by another level of indirection" people .

    > If you have your / on an LV, you can hook up
    > a new disk and *move your / to that disk while the system is running*,
    > which is a pretty cool thing to be able to do.


    Yes? I've never tried this, and I'd have assumed that this wouldn't work
    because *something* would have an open descriptor on / thus preventing
    the umount of the previous /. Not so? Pretty nice.

    >
    >>> [Sorry for the rant ...]

    >> Yeah, what's that about? Did LVM kick you as a child or something
    >>?

    >
    > LVM is more complicated, and nothing but Linux can understand LVM right
    > now. This makes it a bad idea, IMHO, to use LVM unless the box is only
    > running Linux, or if the other OS(es) will never need to access the
    > stuff on the LVs.


    That's okay; I've yet to be convinced that running anything other than
    Linux is a good idea nowadays. However, I'll be taking a look at Solaris
    10 shortly (the last version I've used being 8), so we'll see how my
    opinion evolves.

    - Andrew



  16. Re: Can a (second) hard disc consist of only 1 extended/logical partition? Or is at least one primary necessary?

    Andrew Gideon staggered into the Black Sun and said:
    > On Tue, 22 Apr 2008 17:47:07 +0000, Dances With Crows wrote:
    >> It's not so much that GRUB *can't* understand LVM, but that LVM is
    >> complex enough that it'd be a complete and total PITA to implement an
    >> LVM reader in real-mode x86 code.

    > I didn't write "can't"; I wrote "doesn't". Please don't misunderstand
    > me; what I wrote wasn't a complaint. Given the number of file systems
    > "out there", it's not unreasonable for GRUB to require /boot be in
    > some very limited set of file systems


    LVM is orthogonal to filesystems. You can have any filesystem you want
    inside of an LV. The real problem is that an LV's sectors can be
    distributed among a number of PVs, and when you combine that with the
    need for the BIOS to be able to read every sector, you end up with a
    Real Mess that has no practical solution in the general case.

    >> "It's a hell of a lot easier to resize an LV than it is to resize a
    >> partition" in other words.

    > True, but the reason is that level of indirection. I think it worthy
    > to mention that frequently, but I'm one of those "no problem cannot be
    > solved by another level of indirection" people .


    ....except the "too many levels of indirection have caused performance to
    suck basketballs through capillary tubes" problem (-: . BTDTGTTS.

    >> If you have your / on an LV, you can hook up a new disk and *move
    >> your / to that disk while the system is running*, which is a pretty
    >> cool thing to be able to do.

    > Yes? I've never tried this, and I'd have assumed that this wouldn't
    > work because *something* would have an open descriptor on / thus
    > preventing the umount of the previous /.


    You can't umount / while the system is running. If / is on an LV which
    resides on a PV, you can move it using pvmove.

    >> LVM is more complicated, and nothing but Linux can understand LVM
    >> right now. This makes it a bad idea, IMHO, to use LVM unless the box
    >> is only running Linux, or if the other OS(es) will never need to
    >> access the stuff on the LVs.

    > That's okay; I've yet to be convinced that running anything other than
    > Linux is a good idea nowadays.


    You've never had to deal with brain-damaged suits who think that
    I.Exploder is the only browser in existence, and who hard-code
    dependence on that into their company's main website? BTDT, though
    having a 2K install on virtualbox got around that idiocy.

    --
    "Assembly of God". Haven't you ever wondered what goes on in a place
    like that? What kinds of parts does God need? --Slacquer
    My blog and resume: http://crow202.dyndns.org:8080/wordpress/
    Matt G|There is no Darkness in Eternity/But only Light too dim for us to see

  17. Re: Can a (second) hard disc consist of only 1 extended/logicalpartition? Or is at least one primary necessary?

    On Thu, 24 Apr 2008 14:14:54 +0000, Dances With Crows wrote:


    > LVM is orthogonal to filesystems.


    If you want to be pedantic, that's true. But it's still the case that
    Grub would need to be able to read LVM volumes (and then the filesystem
    installed on a given volume) to eliminate the need to have a non-LVMed /
    boot. As has been mentioned, this isn't too likely [anytime soon].

    [...]


    > You can't umount / while the system is running. If / is on an LV which
    > resides on a PV, you can move it using pvmove.


    I guess I don't understand your point. One can move / with the system
    down regardless of whether it is in an LVM volume.

    [...]

    >> That's okay; I've yet to be convinced that running anything other than
    >> Linux is a good idea nowadays.

    >
    > You've never had to deal with brain-damaged suits who think that
    > I.Exploder is the only browser in existence


    That's true. I'm careful about the work I agree to do. And where I
    work, the two owners have MS degrees in computer science, not "business
    science" (or whatever you'd call that studied to achieve an MBA {8^).

    - Andrew

  18. Re: Can a (second) hard disc consist of only 1 extended/logical partition? Or is at least one primary necessary?

    In comp.os.linux.hardware VanguardLH wrote:

    | After the BIOS completes its POST (power-on self test), it loads the
    | bootstrap program from the MBR (master boot record) from the first hard
    | disk that it finds. The first sector of the hard disk is the MBR and is
    | not allocated to any partition (as well as the remaining 62 sectors of
    | the first track on the hard since tracks are assigned in 63-sector
    | increments). The first 446 bytes are the bootstrap program. So the
    | BIOS needs to load the bootstrap program into memory and pass control to
    | it. The BIOS *only* looks for the bootstrap program from the MBR on the
    | *first* hard disk detected.

    That should be "WHEN tracks are assigned in 63-sector increments".
    Although all hard drives today do use that number as the default, at one
    time that was not true. You can still label/format the drive to specify a
    different value, as well. I've done this specifying 8-sector increments
    and it works fine in Linux (have not tested other systems). I regularly
    do that on my USB flash keys. I'd do it on my SD(HC) memory cards if my
    camera would accept it. But for some reason it gets confused, so I leave
    it in the form originally on the memory card when I got it (I saved a
    compressed copy of the original content image of the memory card so I
    can restore it, as a means to reset the card).


    | This is the old BIOS scheme of how to boot a system. The BIOS loads the
    | bootstrap program in the MBR from the first detected hard disk which
    | reads the partition tables in the same MBR to then load the OS boot
    | loader in the primary partition marked as active and which can only
    | reside on the same hard disk since partition tables only delineate areas
    | on that hard disk. Other software-based schemes have evolved that
    | replace the OS boot loader in the first sector of the partition (that
    | the MBR bootstrap loaded), the OS loader lets you specify from where to
    | load the actual OS (like Microsoft's dual-boot), or they replace the MBR
    | bootstrap program to eliminate the restriction that the boot partition
    | is primary or even has to be on the same hard disk. So with a multiboot
    | manager replacement for the bootstrap program, you can boot to any type
    | of partition (primary or to a logical drive under an extended partition)
    | which can be on any hard disk. Some BIOSes have been extended to
    | perform the same functionality as the software multiboot managers to
    | allow booting from any partition or logical drive on any hard disk.

    And some even allow booting from a specific sector offset from the whole
    disk, allowing placement of the kernel image (or stage 2 image of a boot
    loader) in the space intentionally left between partitions. You better
    know what you are doing if you want to do stuff like that; it's not for
    newbies in a production environment.

    --
    |WARNING: Due to extreme spam, I no longer see any articles originating from |
    | Google Groups. If you want your postings to be seen by more readers |
    | you will need to find a different place to post on Usenet. |
    | Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |

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