I love how the first comment praises it for being "straightforward". For reference, this is how you shrink a file system on Windows:
diskpart
select volume C:
shrink desired=4096
I guess it's nice that the Linux version lets you move the partition as well (or "shrink from behind", so to speak), but damn, "straightforward" is not a word I would have used to describe it.
I think by straightforward they mean you can follow it properly, that's because it's a full step by step that explains each step in enough details to be used, and even includes details for "what to do if you're not in the state expected".
A lot of such guides have a fair amount of "then use tool X to do important part Y" without explaining any of it, making it horrible if you don't know X or the details of Y.
Source: I once tried to fix and resize half-broken LVM volumes and if the sonology guys didn't take time to help me I would probably have just ended up wiping it all and recovering all 16 TB from backups because internet self help is still a harsh place on some linux fs matter.
They asked a permission and for me to fill a form so that they could remote connect to my NAS, and after investigating gave me on the support chat/list thingy the commands that they thought would fix it but they wouldn't run them themselves. Ended up working (issue was that a power failure happened during a shr2 reshape, and while the lvm volume had recovered mdadm hadn't and was blocked in a failed reshape loop, since it was a mix of mdadm and synology's own shr2 [which uses lvm to achieve its goal] trying to find help on the internet was next to impossible, which is why without them I would have wiped the whole thing).
Was as a personnal customer and no paid support (beside having bought the product of course), within the second year of my purchase. Overall I've had a fair amount of support requests with them for my personnal NASes and the couple dozen I manage for professionnal purpose, and I'm very happy with that relationship.
PS: my original support request was very detailled though, I did not just go and ask "doesn't work, fix it !"
And this is how to shrink a mounted filesystem in Linux when you use btrfs:
btrfs filesystem resize 4g /
It's just not supported for ext4. You can grow an ext4 file system, even when it is your currently mounted root, just not shrink it. While it's great that NTFS does (now) support it few other file systems do because it's a relatively uncommon and quite risky.
I certainly wouldn't shrink mounted filesystems even on those that support it because storage systems are quite fickle and the threat of silent corruption is real.
For most filesystems what you normally do is a full dump and restore. Closing all file handles and live migrating to a moved root filesystem is someone's idea of a showing off, it is absolutely not something anyone would do in production.
Does that also shrink the partition? Otherwise you're not comparing equivalent things...
P.S. I realize an existence proof makes us mathematically happy, but it's a little disingenuous to suggest file system experience on Linux and Windows is comparable merely because of the existence of some uncommon file system with similar capabilities. The reality is most Linux users are on ext4 rather than on btrfs or zfs, and most Windows users are on NTFS rather than ReFS or FAT32, so their experience with shrinking file systems is not going to be remotely comparable.
Well, the answer more like "it depends on what you want, exactly".
In the specific example of btrfs there is an extra layer of indirection just like there is with ZFS. Filesystems live inside pools of devices, and when one is shrunk that leaves room for another one to grow. You wouldn't want to resize the physical volume or partition unless the device is shared with other types of filesystems.
(This is why ZFS and btrfs sometimes are referred to as "layering violations". Other filesystems expect the logical volume manager to pool devices into logical block devices.)
So resizing an btrfs filesystem absolutely makes sense even in isolation.
What you describe is accurate for ZFS, but not for btrfs. Shrinking a btrfs filesystem with the resize command only makes sense if you are going to follow up by shrinking the partition or other underlying logical block device (eg lvm). btrfs does not have ZFS's concept of a device pool from which multiple filesystems can be allocated.
It's close enough. A completely valid use case for shrinking a btrfs file system is to remove one of the physical volumes from it, of which there can be several. They can also be split into subvolumes, which is the canonical use case for partitioning your block storage.
Neither of those use cases involves the `btrfs filesystem resize` command. Removing a physical device is accomplished with `btrfs device remove`, and subvolumes don't have a capacity unless you enable the optional quota features (and even then, quota groups use thin provisioning, so setting a lower quota limit doesn't free up any space for anything else).
You can also resize partitions online in Linux. The point of the article was how to migrate the running system into memory and then wipe and reinstall the system. Try doing that from Windows :)
He is not talking about the article but the stack overflow question and answer of parent; and the point of that is to resize the root partition without booting into another OS, not to wipe or migrate to memory (ergo the question being asked: "How to shrink root filesystem without booting a livecd").
You can do that just fine on Windows, hell you can even do it with a nice GUI using computer management.
It's far more generic but also practically useless for an end-user. Really, its only use seems to be for someone who is a remote sysadmin of some sort. You have to stop pretty much everything on the computer, and still go through a reboot. The only difference thing it buys you is being able to stay SSH'd at the cost of wasting so much more time and going through so much more risk and inconvenience. On Windows you'd just shrink and keep using the system as usual.
>It's far more generic but also practically useless for an end-user.
Do end-users really mess with partitioning usually (outside of formatting brand new disks I suppose)? I'm not asking rhetorically, I suppose there must be a use case if MS implemented this (tricky) feature but I can't really imagine any of my non-techies friends and relative decide to shrink a partition (actually most of them probably aren't aware of the concept of partition in the first place).
Replacing your hard drive by a larger one, duplicate partitions and then resize them is very common in the windows end user world, including with root partition (eg replace by a ssd, or a larger ssd). There are lots of paid tools to help do that, notably the duplicate part.
Now personnaly I find it weird, I would rather use the excuse to wipe and start clean if root, and for non root just making the partition you want and copy the content instead feels cleaner, but is it fairly common nonetheless.
They indeed don't know the concept of partitions, but they google "replace my hard drive by a larger one" and follow a guide usually (and such guide contains link to a specific duplicate took they can buy, of course).
"End-user" is not a synonym for "layman". Are you a developer? Do you work on your laptop? Great, you're an end-user.
More generally, I was trying to approximate "the set of users who aren't solely sysadmins of remote systems". Substitute for it whatever word you see fit.
I fully expect a developer to be able to follow the instructions given in the post then. It's not more complicated than your average framework or build system.
> I fully expect a developer to be able to follow the instructions given in the post then. It's not more complicated than your average framework or build system.
And I never suggested a developer would be incapable of following these. Seems like you got so sidetracked in arguing that you forgot what the discussion was actually about. See my original comment: https://news.ycombinator.com/item?id=19357672
I recently installed ubuntu and there was no warning that the previous (many years ago) functionality of a default swap sized large enough to allow for hibernation was no longer the case. I installed using defaults without much thought because of course why wouldn't hibernation be possible using the default. Now I want to resize my partitions.
I thought you'd still need to reboot on Windows? Last time I tried to do any changes to the system partition I had to reboot for it to take effect.
If this is still the case then it's not really a far comparison to Windows because you could then do the same thing from a boot media in Linux (ie boot into it, resize and you're done). In fact you probably could also do that via a GUI (maybe gparted?).
In any case I do agree that Linux does still leave a lot to be desired when it comes to making some of the more advanced file system operations far more complicated for end users than they need to be.
To be fair, it might have been. I'm not a heavy Windows user but the fact I can't recall the last time I resized the system volume probably says more about how long ago it was.
I'm glad you at least phrased it as a question rather than as an assertion then! There is little more infuriating than a *nix fan blasting Windows in 2019 based on their experience with it 15 years ago.
The "good" Linux answer would be to do the equivalent to your script on parted. I have no idea why an explanation of how to remotely install Linux on a machine while running Linux become the accepted answer.
But about Windows, last year I had to resize the partitions on my work desktop, there are enough restrictions around changing things on the disk that Windows is installed that it became a week long research task for our IT support people.
> But about Windows, last year I had to resize the partitions on my work desktop, there are enough restrictions around changing things on the disk that Windows is installed that it became a week long research task for our IT support people.
You're suggesting the research phase for partition management is somehow easier on Linux than on Windows?
> I have no idea why an explanation of how to remotely install Linux [mess with partitions] on a machine while running Linux
The question was explicitly about shrinking the root filesystem without booting a livecd or any other OS.
Gparted cannot do that directly because the root filesystem cannot be unmounted, and the appropriate answer for nearly everyone else (boot from a livecd and use gparted) doesn't apply because the question explicitly bars this option.
The SO answer creates a root environment and uses `pivot_root`, seems you could "just" duplicate the root filesystem, pivot to that full copy, then unmount the original root and do what you wanted with it?
You can remount the root filesystem elsewhere, but not unmount it while it is still the rootfs. Your suggestion would work but it involves restarting nearly everything and having another partition with enough space to copy everything into. It can be done but is pretty hard in general, so gparted just doesn't support it. If you really want/need to do it, you can do so. Otherwise just use a livecd and make your life easier :)
The question explicitly stated that booting another os wasn't an option, so you are right in this case.
However, you should avoid being in that situation entirely, which is nowadays very feasible: all modern servers include remote management facilities, and all sensible virtual server providers give you some way or another to boot from a network image (and get a console session through VNC).
If your provider doesn't give you these options you should definitely switch providers. Not having this option means that you are always one mistake away from total doom (server won't boot -> you will never ever be able to access it again).
Yeah, admittedly if you don't know what's going on there it might feel pretty convoluted and "wtf am I doing here". OTOH, on Linux you could do this since forever, it's not been that long ago that Windows finally shipped tools to do so. Now actually, Windows seems even more convenient since you can easily shrink a FS that is online. On Linux I'm not even sure that is possible; maybe with btrfs but I never really needed to do that, so I have no idea.
> it's not been that long ago that Windows finally shipped tools to do so
I beg to differ, Computer management > Disk management has allowed you to do that in a visual and safe way since at least windows seven in 2009. God knows since how long the underlying cli commands have been available.
While setting up a new laptop I tried to use it and I ended up having to force kill Disk Management after it was "shrinking" for a couple hours. I think the underlying command had succeeded but it just froze. I've never had that kind of experience with (G)Parted, and I think I still trust the Linux tools more...
This is mostly filesystem-dependent. If you have a LVM or ZFS volume for instance resizing is (usually) trivial. When you think about it resizing and in particular shrinking a filesystem is very much a non-trivial operation behind the curtains, it's not surprising that some filesystems don't support it out of the box especially since it's not a super common operation in the wild in my experience.
Thank you for making me double-check, you're right that ZFS can't shrink volumes but you can use resize2fs to shrink EXT2+ volumes offline relatively easily, see for instance https://blog.shadypixel.com/how-to-shrink-an-lvm-volume-safe... for a LVM + EXT example. What makes you say that it's poorly tested exactly?
Of course if you want to shrink the rootfs without rebooting you'll have to do it while mounted and I'm not sure if that's supported by any Linux FS out there (outside of NFS I suppose). That being said I think that's understandable, implementing resizing of a live FS seems very tricky to get right and not extremely useful IMO.
Can Windows really let you shrink NTFS while mounted? That's a pretty impressive feat if that's true, I wonder what motivated that.
> Can Windows really let you shrink NTFS while mounted?
Yes, I have done it, even on the running system partition, and no reboot required. Just right click the partition in Disk Management and select Shrink. It will calculate the smallest size the partition can shrink to, and you can use that or any larger size.
That will happen when there are unmovable files. There are a few tricks you can do to unlock some of these files, or you can use an external utility that you reboot into.
This article is from a vendor of such a utility, but it also describes how to unlock some of the unmovable files within Windows:
This is a tool that is part of most Linux installers and tested by huge numbers of people, and yet things still went wrong. Shrinking filesystems is hard, and this was offline. Shrinking filesystems online is much harder.
