lvm: created guide to root lv shrinking

wiki/linux/arch-linux/arch-linux.md

@@ -0,0 +1,18 @@
+# Arch Linux
+
+[Arch Linux](https://archlinux.org/) is a rolling-release, general-purpose Linux
+distribution.
+Arch Linux uses the [pacman](./pacman_and_yay.md) package manager.
+The Arch User Repositories (AUR) features community-made packages that can be
+installed with different
+[package manager that inlcude access to the AUR](/wiki/linux/arch-linux/pacman_and_yay.md).
+
+## Installation Medium
+
+For the installation usage of a simple USB key is advised.
+This has to be flashed with the Arch ISO.
+The ISO file can be found on the
+[official website](https://www.archlinux.org/download/).
+The iso can be written on an USB-stick using the command
+`dd bs=4M if=<path to ISO> of=/dev/sdx conv=fsync oflag=direct status=progress`.
+`<path to ISO>` points the command to the location of the ISO file

wiki/linux/arch-linux/installation.md

@@ -2,14 +2,17 @@
 
 This guide is based upon a
 [german arch wiki article](https://wiki.archlinux.de/title/Moderne_Installation_mit_UEFI_und_Verschlüsselung).
+For encryption [dm-crypt](../dm-crypt.md) is used.
+Inside the encrypted partition a logical volume will be created with
+[LVM](../lvm.md).
 
 At the end of this guide a fully functional Arch Linux will be installed.
 
 ## 1. Preparation
 
-Ahead of the installation an Arch boot-stick has to be created. The iso-file can
+Ahead of the installation an Arch boot-stick has to be created as described in
-be found on the [official website](https://www.archlinux.org/download/).
+[the Arch Linux entry](/wiki/linux/arch-linux/arch-linux.md#installation-medium).
-The iso can be written on an USB-stick using `dd`.
+
 After that the USB can be plugged in the system on which Arch should be installed.
 Boot the target system and select `Boot Arch Linux (x86_64)`.
 

wiki/linux/disk-management.md

@@ -1,9 +1,47 @@
 # Disk Management
 
 This article focusses on non-LVM and non-MDADM storage.
-For [LVM](lvm.md), [MDADM](./mdadm.md) and [LUKS volumes](./dm-crypt.md) there
+For [LVM](lvm.md), [NTFS](./ntfs.md), [Samba](./samba.md), [MDADM](./mdadm.md) and [LUKS volumes](./dm-crypt.md) there
 are separate entries.
 
+## Universally Unique identifier
+
+Universally Unique identifier (UUID) are identifiers for informations on
+computer systems.
+Most notably they are used to identify file systems.
+This way the UUID of a file system can be used to identify and
+[mount it](#mounting) persistently and correctly.
+
+By listing the directory `/dev/disk/by-partuuid` all mappings of devices to a
+UUID are displayed.
+
+## Mounting
+
+Mounting a file system makes the files of it accessible to the user.
+The command `mount` is used to manually and temporarily mount file systems.
+Automatic mounting is done by changing the file `/etc/fstab`.
+
+The exact guide on how to mount specific file systems can be found in their
+respecitive wiki entries.
+The following describes the general basics of mounting temporarily and
+persistently.
+
+The basic mount command for temporarily accessing a file system is the
+following:
+`mount <path to partition> <path to mount point>`
+All partitions can be found at `/dev` and the standard mount point is `/mnt` and
+its subfolders.
+
+For automatic mounting the following line has to be adapted and added to the
+file `/etc/fstab`
+`<specified partition>	<path to mount point>   <file system> <additional options>  <dump flag> <fsck order>`
+The partition can be specified by [UUID](#universally-unique-identifier).
+The file system varies and a file system specific guide on how to mount them
+can be found in their respective entries.
+The dump flag signals if the file system should be dumped.
+The `fsck` order signals if a file system should be checked at boot.
+Boot partitions should be flagged with a `1` for this reason, otherwise `0`.
+
 ## Create Partition
 
 In the following it is assumed that the disk is `/dev/sda`
@@ -13,7 +51,10 @@ In the following it is assumed that the disk is `/dev/sda`
 - create a primary partition (ext4 format) with `mkpart primary 2048s 100%`
 - `quit` parted
 
-## Grow non-LVM ext4 partition
+`<path to partition>` points to the partition that will be enlarged (for
+example `/dev/sda2`).
+
+## Grow non-LVM partition
 
 ATTENTION: Please note that the partition to enlarge has to be the last one with
 the free space after it.
@@ -28,7 +69,33 @@ the last step (alternatively you can insert `100%` as end, if you want to add al
 the available free space to the partition)
 - `quit` parted
 
-Now you need to resize the filesystem with `resize2fs /dev/sda2`.
+Afterwards the file system need to be resized as described in a
+[later section](#growing-a-file-system).
+
+## Growing a File System
+
+A file system can easily be resized if free space is available on the partition
+it is stored in.
+The free space has to be placed behind the partition.
+This can be done by running the following command:
+
+```sh
+sudo resize2fs <path to partition>
+```
+
+## Shrinking a File System
+
+To shrink a file system the `resize2fs` command will be used aswell as `e2fsck`.
+First the file system needs to be checked for size aswell as data distribution.
+This can be done using the command `sudo e2fsck -f <path to partition>`.
+`<path to partition>` directs to the volume whose file system should be
+shrinked - for example `/dev/sda1`.
+It has to be the same for the next step aswell.
+Afterwards the file system can be shrinked with the command
+`sudo resize2fs <path to partition> <new size of the file system>`.
+`<new size of the file system>` is the size that the file system will be
+shrunken to in the usual notation (for example `12G`).
+Especially for large file systems this might take a while.
 
 ## Error solving
 

wiki/linux/dislocker.md

@@ -12,7 +12,7 @@ package.
 
 ### Manual Mounting of Bitlocker Partition
 
-For the [mounting](/wiki/linux/filesystems.md#mounting) to work two directories
+For the [mounting](/wiki/linux/disk-management.md#mounting) to work two directories
 are required.
 One to mount the `dislocker-file` (`/mnt/bitlocker`) and one to mount the
 [windows volume](/wiki/linux/ntfs.md#manual-mounting) (`/mnt/windows`).
@@ -35,10 +35,10 @@ or another mount point as described in the
 
 ### Automatic Mounting at Boot
 
-Using [fstab](/wiki/linux/filesystems.md#mounting) the partition encrypted with
+Using [fstab](/wiki/linux/disk-management.md#mounting) the partition encrypted with
 Bitlocker can be automatically mounted.
 The following lines have to be adapted and written into
-[`/etc/fstab`](/wiki/linux/filesystems.md#mounting).
+[`/etc/fstab`](/wiki/linux/disk-management.md#mounting).
 In this case the intermediary dislocker file `dislocker-file` is mounted to
 `/mnt/bitlocker`.
 

wiki/linux/dm-crypt.md

@@ -171,7 +171,7 @@ Additionally the following lines has to be adapted and added to the file
 
 `<mapping location>` has to be the same as chosen in the step before.
 `<UUID of encrypted volume>` is the
-[universally unique identifier](/wiki/linux/filesystems.md#universally-unique-identifier)
+[universally unique identifier](/wiki/linux/disk-management.md#universally-unique-identifier)
 of the volume.
 `<location of key file>` describes the location where to find the key file
 created in the previous step.

wiki/linux/filesystems.md

@@ -1,50 +0,0 @@
-# File Systems
-
-File systems control how data on a drive is stored.
-
-- [NTFS](./ntfs.md) is a proprietary file system used by Windows which can
-  additionally be encrypted with [Bitlocker](./dislocker.md).
-- [Samba](./samba.md) is free windows interoperability software that is not a
-  classic file system can be mounted so it will be mentioned here
-- [DM-Crypt] is an encryption service. Volumes encrypted with it follow a
-  special decryption process.
-
-
-## Mounting
-
-Mounting a file system makes the files of it accessible to the user.
-The command `mount` is used to manually and temporarily mount file systems.
-Automatic mounting is done by changing the file `/etc/fstab`.
-
-The exact guide on how to mount specific file systems can be found in their
-respecitive wiki entries.
-The following describes the general basics of mounting temporarily and
-persistently.
-
-The basic mount command for temporarily accessing a file system is the
-following:
-`mount <path to partition> <path to mount point>`
-All partitions can be found at `/dev` and the standard mount point is `/mnt` and
-its subfolders.
-
-For automatic mounting the following line has to be adapted and added to the
-file `/etc/fstab`
-`<specified partition>	<path to mount point>   <file system> <additional options>  <dump flag> <fsck order>`
-The partition can be specified by [UUID](#universally-unique-identifier).
-The file system varies and a file system specific guide on how to mount them
-can be found in their respective entries.
-The dump flag signals if the file system should be dumped.
-The `fsck` order signals if a file system should be checked at boot.
-Boot partitions should be flagged with a `1` for this reason, otherwise `0`.
-
-## Universally Unique identifier
-
-Universally Unique identifier (UUID) are identifiers for informations on
-computer systems.
-Most notably they are used to identify file systems.
-This way the UUID of a file system can be used to identify and
-[mount it](#mounting) persistently and correctly.
-
-By listing the directory `/dev/disk/by-partuuid` all mappings of devices to a
-UUID are displayed.
-

wiki/linux/lvm.md

@@ -4,7 +4,7 @@
 
 ## Usage
 
-### Create VG for proxmox
+### Create Volume Group for Proxmox
 
 We will use `/dev/sdb` as our drive.
 Setup the disk for the physical volume with `sgdisk -N 1 /dev/sdb`.
@@ -15,7 +15,7 @@ This can be solved by removing the old partition table with `wipefs -a /dev/sdb`
 And finally create the volume group `vgcreate vmdata /dev/sdb`.
 Then follow the guide in proxmox on how to connect a `vg` to proxmox.
 
-### Add Drive to existing volume group
+### Add Physical Volume to Existing Volume Group
 
 First format the disk so that it has one partition (we will assume its called
 `/dev/sdc1`).
@@ -26,7 +26,24 @@ pvcreate /dev/sdc1
 vgextend <name of your volume group> /dev/sdc1
 ```
 
-### Resize a physical volume
+### Remove Physical Volume
+
+Before removing a physical volume it has to be confirmed that it is not part of
+any volume group.
+This can be done by running `sudo pvs` and confirm it is not listed for any
+logical volumes.
+If it is [a later section](#shrink-size-of-a-logical-volume) how the physical
+volume can be completely emptied and removed from the logical volume.
+A physical volume can be removed by running the following command:
+
+```sh
+sudo pvremove <path to physical volume>
+```
+
+`<path to physical volume>` is the physical volume that will get removed.
+
+
+### Resize a Physical Volume
 
 To increase the size of a physical volume you have to have free free space
 in the partition containing the physical volume.
@@ -38,7 +55,7 @@ encrypted with LUKS a guide is available in
 To resize the physical volume to the size of the containing volume run:
 `pvresize /dev/mapper/<name of physical volume>`
 
-### Increase size of a logical volume
+### Increase Size of a Logical Volume
 
 To increase the size of the logical volume you have to have free space in the
 according volume group. You can check that by running: `vgdisplay`.
@@ -61,3 +78,89 @@ Now you need to extend the filesystem with:
 ```sh
 resize2fs /dev/<volume group>/<logical volume>
 ```
+
+### Shrink Size of a Logical Volume
+
+When trying to shrink a logical volume caution is advised as data can easily be
+destroyed by mistyping commands of paths.
+This section is based on a guide given by
+[telcoM](https://unix.stackexchange.com/questions/591389/how-to-remove-a-disk-from-an-lvm-partition).
+First of all the volumes have to be unmounted and not used by any programs or
+services other than the following commands.
+
+If the volume to shrink is the root volume it has to be done offline.
+For that a simple installation stick is enough.
+[The Arch Linux entry](/wiki/linux/arch-linux/arch-linux.md#installation-medium)
+describes the creation of such a boot stick.
+Afterwards the operating system has to be booted from the just created stick or
+a comparable device.
+For non-root volumes this extra step can be skipped.
+
+The volume group needs to be activated by running the command
+`sudo vgchange -ay <volume group>`.
+`<volume group>` is the name of the volumegroup that features the logical volume
+to shrink.
+Then the file system needs to be resized.
+For safety reasons make the file system exactly as big or smaller than the
+future logical volume.
+The process of shrinking a filesystem is explained in the
+[file system entry](/wiki/linux/disk-management.md#shrinking-a-file-system).
+The partition to shrink in this case is the logical volume.
+This is the only step that needs to be done offline for root volumes.
+Rebooting to the root volume at this moment is advised.
+
+The next step will shrink the logical volume itself.
+This will be done by running the following command:
+
+```sh
+sudo lvreduce -L <new size of logical volume> /dev/mapper/<volume group>-<logical volume>
+```
+
+Again this statement has to be adapted accordingly.
+`new size of logical volume` describes the new size the logical volume will have
+after successful completion of the command.
+It is important for this to be exactly the same or larger than the size given
+into the resizing of the file system with `resize2fs`.
+
+### Remove Physical Volume from Volume Group
+
+This section describes the removal of a physical volume from a logical volume.
+First the command `vgs <volume group>` has to be run.
+`<volume group>` is the name of the volume group belonging to the logical volume
+a physical volume should be removed from.
+It has to be ensured, that enough free space (`VFree`) on all physical volumes
+(except the ones to remove) is available to remove a physical volume from the
+volume group.
+There has to be equal or more free space than the size (`VSize`) of the physical
+volume that will be removed.
+Otherwise an [earlier section](#shrink-size-of-a-logical-volume) explains how to
+shrink a logical volume.
+The logical volume has to be shrunk according to the described ration between
+`VFree` and `VSize`.
+
+The following command will distribute the contents of a physical volume onto
+other physical volumes available:
+
+```sh
+sudo pvmove <path to physical volume>
+```
+
+`<path to physical volume>` is the physical volume that will get emptied and
+later removed from the logical volume.
+Afterwards the physical volume is emptied and can be removed from the logical
+volume by running the following command:
+
+```sh
+sudo vgreduce <logical volume> <path to physical volume>
+```
+
+`<logical volume>` is the name of the logical volume.
+After this command the physical volume is no longer a part of it.
+
+If no longer used the empty physical volume can then be removed as described in
+the [according section](#remove-physical-volume).
+
+Afterwards the file system can be matched to the logical volume so it takes up
+the full new size.
+This is explained in
+

wiki/linux/ntfs.md

@@ -1,6 +1,6 @@
 # NTFS
 
-NTFS is the proprietary [file system](./filesystems.md) of Windows.
+NTFS is the proprietary [file system](./disk-management.md) of Windows.
 
 ## Setup
 
@@ -9,7 +9,7 @@ distributions - has to be installed.
 
 ## Usage
 
-When [mounting](/wiki/linux/filesystems.md#mounting) a
+When [mounting](/wiki/linux/disk-management.md#mounting) a
 [Bitlocker encrypted drive](./dislocker.md) there are additional steps that have
 to be taken to decrypt the device.