eCS: Installing

(At least for now, this page--mainly about things to think through before beginning the install process--is what there is here; more about the process itself might be added later.

(The other pre-install topic needing thought, but not covered here, is using the "Advanced Installation" option to leave off installation of any "lite" software for which you plan to acquire and install the full-strength version--often, installing a full-strength version over a "lite" version is a pain in the elbow, so it is best to leave the "lite" version off altogether. One example of such a product is the excellent XWorkPlace package, of which, left to itself, the "Easy Installation" will put a lite form called eWorkPlace on your system. See the Tips'n'Tricks page listed below under "More Resources" for details.)


Pre-Installation Drive Planning:

Basic Concepts

To plan your eCS installation, and to successfully implement your plan, you must understand certain terms. Because the "Logical Volume Manager" (LVM) program that comes with eCS has some new features, it is best to begin at the very beginning in explaining the key terms.

Aside from "volatile" (goes away when you turn the computer off) storage memory--typically RAM--all of your operating system (OS), other programs, and data are stored on devices that your computer accesses to get at those programs and data. Under eCS, those devices are, for historical reasons, commonly termed drives, which is a most unfortunate term, because it can cause confuson with real, physical "drives" (such as hard disks or CD readers). A "drive", for our purposes, is some data storing/supplying resource that your operating system "sees" as a single, distinct entity--not (necessarily) a physical device; physical "hard drives" we will call disks.

(Be aware that some operating systems other than eCS--most notably Linux and all the rest of the *nix-family systems--do not use the same approach to handling storage-device access; the explanations here apply only to eCS and OS/2, though they mostly apply to the Windows family as well, and even DOS.)

Also for historical reasons, such "drives" are designated by single letters of the alphabet, which places an immediate upper limit--26--on the number of distinct drives that eCS can recognize. Moreover, the first two letters of the alphabet, A and B, are always reserved to designate diskette drives, even if there is only one such drive, or no such drive at all, in a given system.

Normally, resources other than hard disks are each assigned as a single "drive"--so if you had, say, a CD-ROM drive and two optical (DVD) R-W drives, those would each be recognized as a distinct "drive" and would require, between them, three alphabet letters.

When you power up your computer, micro-programs stored in the chips making up your system's "BIOS" load certain portions of your OS into memory and start them running; those, in turn, bring in the rest of the operating system and such of your other programs as the OS starts at powerup. This process is referred to as "booting", from the old reference to "pulling oneself up by one's bootstraps".

To boot up, the BIOS needs to know where the OS is to be found, and it will look for it in an order that depends on settings in the BIOS (which can be user-changed, but BIOS-setting changes are unwise for the inexperienced), but which is typically:

  1. on a diskette in diskette drive A,
  2. on a hard disk, or
  3. on a CD or DVD in an appropriate drive.

Except in special cases (such as initial install from a CD), we will have our operating system, and the programs we run on it, and the data for all of them, stored on one or more hard disks. We thus now need to focus on how individual, physical hard disks relate to "drive" resources under eCS and LVM.


How Hard-Disk Space Is Conceived

"Partitions"

The space on any one hard disk can be divided up into various sections that computer software will see as distinct units. For--yes, again--historical reasons, the maximum number of such segments or sections on any one disk is four. Such segmentation is recorded in a small (512-byte) but crucial bit of space on the disk called the "Master Boot Record" (MBR); the MBR keeps track of the number of segments and their actual, physical locations on the disk.

Such segments or sections are called (and this is the first crucial term to learn) primary partitions. They are "primary" because they are recorded directly in the MBR.

(Way back when, it was supposed that one might want more than one OS on a system, and the "partition" concept was devised as a way to, in effect, break one disk into up to four disks, each of which would be used wholly by a particular operating system; that's why four was thought an ample number.)

When the BIOS goes to look for the OS on a hard disk, it relies on the MBR to tell it from which of the existing partitions to start loading bootup instructions. That partition is said to be the active partition, or to be marked active in the MBR.

Rather obviously, if you have only one hard disk, and that one was set up as one single, all-encompassing partition, the MBR will necessarily point at that one partition. But such a set-up is uncommon: users typically find it useful, or even necessary, to partition their hard disks into multiple partitions.

If you have more than one physical disk, you may--and probably will--have disks that have no active partition, since your OS will be on some one drive only.

But what if you have more than one hard disk, and more than one of those disks has an "active" partition? What happens depends on the details of the BIOS in your particular computer: different kinds handle the issue in different ways. Such setups are distinctly unusual: almost everyone has all their bootable partitions on some one drive, the one that their BIOS sees as the "first" hard drive--with what "first" means being beyond our scope here.

Today, four partitions is not a lot, especially considering that there may be up to 24 assignable drive letters. Thus, disk design evolved to allow one of the primary partitions on a disk to be marked in the MBR as an "extended" partition (your next crucial term). An extended partition can be subdivided into any number of what are normally referred to as "logical drives" (occasionally called "logical partitions", which can be confusing), which are independent units that are in most ways effectively--but not actually--further partitions. But, again: there can only be a single extended partition on a given physical disk.

(And "any number of" is still limited by the alphabet letters available to designate such subdivided logical drives.)


"Volumes"

In older operating systems, what we have called a "drive" was either a primary partition or one of the "logical drives" in an extended primary partition, and the term "volume" was then synomous with a "drive" letter; but under the new LVM-based management scheme, that is no longer so. We have more options--but to use them, we need to understand them.

Under LVM, it remains true that a "drive"--a resource uniquely identified by a letter of the alphabet--is a "volume", and for clarity we will from here on out call such things "volumes". But now, a volume is not tied to a particular partition, primary or logical: it can be made up of multiple partitions--even partitions that reside on physically distinct disks.

There is nothing "automatic" about volumes: just like partitions, they do not exist till you create them with LVM. You can explicitly first create the wanted partitions, then make volumes from them (which allows you control over where, physically, the partitions will reside on the disk), or you can use the "Allocate from free space" option of LVM, under which the needed partition is made "on the fly" by LVM and assigned to the volume you are creating. (There are subtle performance-related consequences of where on a disk a given partition is relative to its typical usage load.)

(LVM was designed expressly to emphasize to users a "logical"--as opposed to physical--view of disks; you will rarely if ever find reference to "extended partitions" in LVM documentation, except by third parties. The eCS Manual expressly states "LVM hides the numbers, size and location of physical partitions from users." That is not quite true, but it demonstrates the intent.)

All the partitions that you, using LVM, allot to a given volume are treated by the OS as a single resource. So your "Drive F" could be spread, in a physical sense (which is normally transparent to you), over, say, as much as seven (or more) chunks of disk space on three (or more) different disks.

LVM can create two distinct kinds of volumes ("Compatible" or "LVM"); what those are and why are discussed farther below, at "Multi-OS Complications".


"Bootable" Volumes and Boot Manager

Bootable Volumes

You cannot install your OS on just any old volume: a volume needs to be expressly set as "bootable" (by you, when you create it). Nor can just any old volume be set bootable: it needs to meet certain criteria, those being (for eCS) that it:

  1. comprise only a single partition, or be a logical drive;
  2. be a "Compatible" volume (discussed farther below)--which automatically enforces the requirement above; and
  3. not be formatted as a "JFS" volume (discussed farther below).
Boot Manager

Many users will want more than one bootable volume. Some will be using multiple operating systems on the same computer--say, for example, eCS and Linux; even those running purely eCS will often want a second "maintenance" (emergency backup/repair resource) bootable volume. When more than one volume is to be bootable, your computer (meaning its BIOS) needs a way to ask you which volume to boot from. Software to handle that matter is typically referred to as a Boot Manager (BM).

Using the LVM that comes with eCS, you can install a suitable BM. You should definitely always do this at first install, even if you run only eCS and don't presently want a maintenance partition, because your plans may change later and putting BM in on an established disk can create needless complications. Be aware that BM, though relatively small, always requires a dedicated primary partition--so, at least on your first drive (if you have more than one), only three primary partitions are left for other purposes.

Note that when you have a BM in place, necessarily the MBR points to the BM's partition as the "active" one. The BIOS "boots" (loads in and runs) BM, which then passes off actual booting to whatever bootable OS partition the BM selects. While a BM can be set up simply as a menu from which the user selects an OS, much more commonly it is set up to default to some one OS unless the user manually intervenes during some brief time window (typically 5 to 15 seconds) during the boot-up process.

If you have multiple hard disks, BM (and, of course, the OSes it will manage) can only reside on either the first or the second of those disks (in the order that your BIOS sees them). Most people just put it and the OSes on the first drive, but now you know.

(BM is normally the first thing one installs on a blank, new disk, and so is placed at the beginning of disk space. Because BM is itself a primary partition, it cannot lie in the midst of a logical partition, so--to avoid "blocking off" usable disk space--it should only be placed at the very beginning or very end of usable disk space. There are occasionally, for certain particular system setups, reasons to want it at the end, and tricks for getting LVM to put it there, but those are beyond our scope here--if you need this, you will probably already know why and how.)

File Systems

Before being usable for data storage, every hard-disk volume has to be "formatted" to a space-layout scheme corresponding to some standard method of file organization. Old DOS used something called the "File-Allocation Table" system (FAT), which is still available under eCS, and is efficient for rather small volumes (such as a bare-bones-type "maintenance volume" might be). Till recently, the best general-use format available was the "High Performance File System" (HPFS). Now, though, there are other formats, notably the "Journalling File System" (JFS), that many people consider superior to HPFS.

Regrettably, for now (this may change soon) eCS cannot be booted from a volume formatted as JFS--so, for a bootable volume you will want to format that volume as HPFS (or, if it's a very small volume, as for a bare-bones "maintenance" bootable, perhaps the old FAT file system).


Optimally Organizing a Disk

So we see that if you are using just eCS, you could (after installing Boot Manager in a primary partition of its own) simply make all the rest of the disk one second extended primary partition, and carve out a bootable logical volume and even a second, backup "maintenance" bootable volume, plus as many other program and data volumes as your heart desires and the alphabet allows.

It is, though, wise here to apply some forethough and consider whether you want, or think you might ever want, to install any other OS on the same disk. Even if you don't think so just now, prudence suggests that you consider that times change, and opinions with them. Especially in light of the almost comically huge size of modern hard disks--with 250 GB presently being more or less the norm for new drives--it behooves one to leave unused disk space sufficient for some future installation of one, or even two, other OSes (each of which can thus have a primary partition all to itself). And if, after some time, you haven't installed any other OSes and find you need that space, you still have it available anyway. (You could even use it to expand some existing volume or volumes--recall that the LVM can create multi-partition volumes.)

The eCS extended partition ideally wants two bootable volumes: one, preferably Drive C, for the actual operating system install, and another (might as well be Drive D) for a "maintenance partition", for use in case of either some corruption occurring on Drive C, or as a backup if one wants to later install an eCS upgrade from scratch on a wiped Drive C. While some users make only a stripped-down "bare-bones" maintenance volume, it makes more sense to just do a second full install on Drive D, so you have available all the same full functionality you're used to. (But it makes sense to wait till you are confident that your main install is working just as you want and expect, so you know exactly what to do or not do in installing the second version).

The bootable volumes will each want to be "Compatible Volumes" (see the next section) formatted (if both are full-blown installs) to HPFS. As to volume size, a common recommendation is about 2 GB, and a practical upper limit is the 4.2 GB that would fill a single plain DVD-RAM (this is discussed more farther on). The only drawback (considering disk capacities) to sizes toward that upper limit is that in the event a CHKDSK is needed, the larger size could materially increase the nontrivial time required. My personal opinion is that CHKDSKs aren't needed very often, whereas operating systems tend to grow and grow; I'd hate to make a couple of 2-GB main OS partitions, then find that in 2007 I need 2½ to 3 GB for the latest OS version. But this is what is called in sports a "judgement call".

The rest of the extended partition one carves up into further logical drives to use for programs and data as one thinks best, each formatted as JFS. Some advocate leaving the whole remainder as one vast logical drive, or at most two, on the ground that JFS is most efficient with larger drives; others like to have drives that will fit in their entirety on one DVD-RAM, which is about 4.2 GB a drive. (But, except on rather small--by modern standards--disks, at least one drive has to be pretty big, as there are only so many letters in the alphabet.) Volume size is another judgement call.


Multi-OS Complications

If you are going to have volumes intended to boot OSes other then eCS, there are two potentially confusing or complex considerations.

First, in eCS (or, technically, any "LVM-aware" OS), the "drive" letters assigned to volumes are "sticky": you can assign any then-unused letter to any new volume--regardless of its physical placement on the disk or of sequentiality--and that letter is that drive's permanent designation under eCS.

Second, the eCS LVM can create two significantly different kinds of volumes:

The chief differences are these: only LVM volumes can comprise multiple partitions, and LVM volumes are "invisible" to OSes that are not "LVM-aware" (most or all OSes except eCS)--they have to be invisible to them because such OSes cannot "understand" a multi-partition volume. (But "LVM volumes" remain invisible even if they only comprise a single partition.) If you are sure that all you will ever boot is eCS, you can and should--to get the multi-partition-volume ability--create all volumes as LVM volumes (remembering, though, that any volume to be a bootable volume must be made as a "Compatible Volume").

The potential complications that arise in multi-OS systems relate to drive-letter correspondences, or rather to the possible lack of them--mismatches between what eCS calls a given volume (say, Drive E) and what a non-LVM-aware OS might call it (perhaps Drive D). These mismatches can arise because non-LVM-aware OSes (we really need an acronym for that term, bit I'm not going to invent one here) do not see either any "LVM Volume" or the "sticky" drive-letter assignments that an LVM-aware OS would see. A non-LVM-aware OS will parcel out drive letters at bootup time according to its private scheme, which is typically the order it finds the volumes (the volumes that it can see, that is) on the disk; it will thus have mismatches if either a) there are one or more "LVM volumes" not at the physical end of the drives on the disk, or b) the LVM-based drive letters were not assigned in the sequence in which their physical volumes appear on the disk.

Such mismatches can potentially--and very probably would--cause huge problems, in that drive letters appear in countless program ini-type files, and often data files themselves. Anyone planning a multi-OS system in which more than one of the OSes needs to "see" any of the same drives as another needs to put great care into their planning of drive assignments on disk. The basic rules would correspond to the two potential sources of mismatch:

(Note carefully that Compatibility volumes cannot span multiple partitions: you are thus back to the old volume=partition=drive scheme.)

But, again, if multiple OSes will not ever need to see any of the same volumes, then you can make all the eCS-only non-bootable volumes as LVM volumes, lettered as you please.


Summary

Let's summarize what we have learned (recalling that these things apply to eCS and many other OSes, but not necessarily all--*nix OSes, in particular, organize things differently):

  1. Many OSes, including eCS, identify the sources of non-volatile storage available to them as "drives", each such drive designated by a single letter of the alphabet. The letters A and B are always reserved to be used for diskette drives (whether or not any are present). Other mechanisms that use "removeable media", such as CD readers, are also designated by letters, typically one per actual, physical unit, as can be some software products that emulate a physical drive; these designations are not reserved or standardized (but eCS gives you some control over their assignment--see farther below).

  2. Hard disks can be, and usually are, divided up into multiple blocks, each of which is a "drive" in the sense just mentioned. Such "drives" are, however, better and less confusingly called "volumes".

  3. Using LVM, any available letter can be assigned to any volume at its creation, and that letter will be that volume's permanent ("sticky") designation--but only to eCS (or any other "LVM-aware" OS).

  4. Using LVM, a volume can be created as one of two types: as a "Compatible Volume", which any OS can see, or as an "LVM Volume", which only eCS (or another "LVM-aware" OS) can see.

  5. Volumes (or "drives") on a physical disk are constituted from partitions, a partition being a user-designated chunk of space (to which the user creating it can give an arbitrary identifying name) on a particular hard disk. Hard disks can each have up to no more than four "primary" partitions, but one (and only one) of those can be designated an "extended" partition, which can be subdivided into numerous "logical" drives.

  6. A volume that is not "bootable" (that is, which cannot carry an operating system) can--under eCS and its LVM--comprise from one to many partitions, even on physically distinct disks; a bootable volume, however, can only comprise a single partition--which, moreover, must be a "Compatible" type volume.

  7. A "Boot Manager" program--which requires a primary partition all to itself--is needed to designate which "bootable" volume will be used if more than one such (as with separate "maintenance" bootable volumes, or other OSes) is present on that disk.

  8. Every volume, to be usable by an OS, must be "formatted" to some fixed scheme known to that OS. Common schemes include FAT (from DOS), HPFS (from Warp), and the new JFS.

  9. Under eCS as it is at present, a bootable volume cannot be formatted to JFS, only to HPFS (or some normally immaterial alternatives), and must be a Compatible Volume.

  10. Because OSes other than eCS ("non-LVM-aware" OSes) cannot "see" either an LVM Volume or the sticky drive letters LVM assigns, such an OS, when booted, can and often will--if not carefully planned for--assign drive-designation letters that do not correspond to those known to eCS (an "LVM-aware" OS); such letter mismatches would probably cause major problems, owing to drive letters stored in data and ini files. "Planning" means assigning eCS volume types and letters in such a way that other OSes will see the volumes visible to them in the same order as the letters assigned to them under eCS.


Installation Notes:

Note! This material is not a step-by-step walk-through of installation, or even an overview of that process; it is only a pointer to a few perhaps nonobvious points about the partition/volume aspects of installing.


Have a Plan

There is an old carpenter's saying: measure twice, cut once.

Before beginning your eCS installation, think very, very carefully through how you want your system to end up configured, and why. Every user will have unique needs and tastes; others can give advice, and it will often be helpful, but you need to make your own final decisions.

That said, one guideline that is widely recommended is this: keep your OS as separate as possible from your other programs and data. The reason is simple: it allows OS updating, or total replacement (which can be the same thing) without risking interference with or damage to the rest of your system. In the end, that means keeping your bootable volume occupied by eCS and nothing but eCS. Even the ancillary apps and utilities that come with eCS--unless they're an integral part of eCS itself--should be placed outside the eCS volume.

Another consideration is facilitating backing up. The modern way to back up is to make data-DVD copies of your system. That is most easily done when two criteria are met: one, that no one volume be bigger than will readily fit on a single DVD; and two, that your volumes are an intelligent separation of content by backup need (that is, that it makes sense to have all the contents of a given volume backed up in one place--for example, don't have different pieces of some one website on different volumes). "Fitting on a single DVD" can mean different things, because there are single-layer and double-layer DVDs. But even a single-layer DVD--the least expensive form--is still roughly 4.2 gigabytes of storage space (the nominal 4.7 GB one often sees quoted is "raw" space--after formatting, file system overhead, and so on, 4.2 is the safest "net space" figure to use), and so is a reasonable upper limit for at least most of one's volumes.

(Note that for serious archiving of data--as opposed to storage of movies or sound tracks--the DVD-RAM format is the clear preference. It uses a read-after-write checking mechanism that makes a slower burn process, but guarantees data accuracy; no serious long-term archiver will use any other DVD format.)

Be especially careful in creating primary partitions: be sure your plan does not require more than four primary partitions a disk, or more than one extended partition a disk.


"Drive"-Letter Allocation

In eCS, there is a designated "reserved" drive letter. What that marks is the last letter eCS will "reserve" for hard-disk volumes; it will use letters starting right after that for any other kinds of drive (such as a DVD burner) that it finds attached. Curiously, the default eCS installer will set R as that reserved letter, which has several drawbacks. If you want, as many will, to change that letter to something farther down the alphabet, you have to do so right at the very start of your install.

You can find more detail at this very useful eCS 1.1 Install Tips'n'Trick page by Walter Metcalf, as well as on pages 44 and on in the eCS Manual (at least in my edition), but in summary:

  1. The very second screen you will see in the install (right after the "boot from eComStation CD-ROM" screen) offers you the choice Boot with menu for own values--select that option.

  2. From the initial options screen, press <PgUp> to get to the next page (which will be the first actual selections page).

  3. <Tab> to the line saying Reserve the following drive letter:, then change the selection from R to whatever you want instead (use the <up> and <down> cursor keys to make your selection); note that the CD-ROM letter allocation on the next line will follow along.

    Note that eCS itself requires the letter Z, and that you should be sure to leave available at least as many letters as you plan ever to have non-hard-disk drive devices; if, say, you will have a CD drive and a separate DVD drive, you would need to leave at least two letters for eCS to use (so you would "reserve" W, leaving X and Y for the devices and Z for eCS's use). You should also take care to leave a further drive letter for other present or future devices, such as LAN drives (you can get by with a single letter if you use something like NetDrive, which allows multiple external resources to be "attached" to your system via a single drive letter).

  4. Exit and continue with the install by pressing the <F10> key (unless there are other things you want to change here as well).


More Resources

These pages ought to be especially useful for planning and executing an eCS install:



Mr. Bob Eager of Tavi Systems, whose knowledge of these matters very far surpasses my own, and whose ceaseless contributions to the OS/2 community can be seen all over usenet as well as at Tavi's OS/2 pages, kindly and with awesome patience walked me through correction of many of my original misunderstandings, and I much thank him; any infelicities of exposition or actual errors of fact that might remain (none, I hope and think) are purely my fault.



©2005, Eric Walker.