Add LVM volume-grow guide; publish iPhone Mirroring + Claude Code login fixes

01-linux/index.md

@@ -23,6 +23,12 @@ A collection of guides covering Linux administration, shell scripting, networkin
 - [Ansible Getting Started](shell-scripting/ansible-getting-started.md)
 - [Bash Scripting Patterns](shell-scripting/bash-scripting-patterns.md)
 
+## Storage
+
+- [SnapRAID & MergerFS Storage Setup](storage/snapraid-mergerfs-setup.md)
+- [mdadm — Rebuilding a RAID Array After Reinstall](storage/mdadm-raid-rebuild.md)
+- [Growing an LVM Volume by Absorbing Another Disk](storage/lvm-grow-volume-absorb-disk.md)
+
 ## Distro-Specific
 
 - [Linux Distro Guide for Beginners](distro-specific/linux-distro-guide-beginners.md)

01-linux/storage/lvm-grow-volume-absorb-disk.md

@@ -0,0 +1,159 @@
+---
+title: "Growing an LVM Volume by Absorbing Another Disk"
+domain: linux
+category: storage
+tags: [lvm, lvextend, vgextend, pvcreate, resize2fs, ext4, storage, disk, homelab]
+status: published
+created: 2026-06-17
+updated: 2026-06-17
+---
+
+# Growing an LVM Volume by Absorbing Another Disk
+
+When an LVM-backed filesystem fills up and its volume group (VG) has no free
+extents, you can grow it by adding a second physical disk as a new physical
+volume (PV), extending the VG onto it, then extending the logical volume (LV)
+and its filesystem. With ext4 this can be done **online** — no unmount, no
+downtime for the volume being grown.
+
+This guide covers the common case where the disk you want to absorb is currently
+in use by its own LVM volume (you must evacuate and tear that down first), and
+the precautions that keep it safe.
+
+> [!warning] This enlarges your failure domain
+> A single LV spanning two disks linearly (the default — no RAID/mirror) means
+> **losing either disk loses the entire volume.** ext4 has no parity. Only do
+> this for data you can rebuild, or layer redundancy (mdadm/LVM RAID) underneath.
+> Back up anything irreplaceable first.
+
+## The Short Answer
+
+If the target disk (`/dev/sdX`) is already empty and unused:
+
+```bash
+sudo pvcreate /dev/sdX
+sudo vgextend myvg /dev/sdX
+sudo lvextend -l +100%FREE /dev/myvg/mylv
+sudo resize2fs /dev/mapper/myvg-mylv      # ext4, online; use xfs_growfs for XFS
+```
+
+The rest of this article handles the harder case: the target disk is currently
+holding its own LVM volume with data on it.
+
+## Step-by-Step
+
+### 1. Survey the current layout
+
+```bash
+sudo pvs                       # physical volumes → which VG each belongs to
+sudo vgs                       # volume groups, free extents (VFree)
+sudo lvs                       # logical volumes and sizes
+lsblk -o NAME,SIZE,TYPE,MOUNTPOINT
+df -h
+```
+
+Confirm:
+
+- The VG you want to grow (`myvg`) has `0` `VFree` (that's why you're here).
+- The disk you want to absorb (`/dev/sdX`) is a **standalone** PV — not a member
+  of an mdadm array, a mergerfs branch, or a SnapRAID parity disk. Repurposing a
+  disk that something else depends on will break that thing silently.
+
+### 2. Evacuate the disk you're about to absorb
+
+Anything on the target disk will be **destroyed**. Move it somewhere with room to
+spare, then prove the copy is intact before you trust it.
+
+```bash
+# Copy preserving permissions/timestamps
+sudo rsync -a /mnt/olddisk/important /destination/with/space/
+
+# Verify byte-for-byte — empty output + exit code 0 means identical
+sudo diff -rq /mnt/olddisk/important /destination/with/space/important && echo OK
+```
+
+For large trees the `diff -rq` (full byte comparison) is slow but is the
+authoritative check — don't skip it before the destructive phase. If an
+application tracks files by path (databases, media servers), update its path
+references to the new location *now*, while the old copy still exists as a
+fallback.
+
+### 3. Unmount and remove the old disk from fstab
+
+```bash
+sudo fuser -m /mnt/olddisk          # confirm nothing holds it open
+sudo umount /mnt/olddisk
+mountpoint -q /mnt/olddisk && echo "STILL MOUNTED" || echo "unmounted"
+
+sudo cp /etc/fstab /etc/fstab.bak-$(date +%Y%m%d)   # always back up fstab
+sudo sed -i '/olddisk/d' /etc/fstab                 # remove the stale entry
+grep olddisk /etc/fstab || echo "fstab line gone"
+```
+
+> [!tip] Verify your `sed` pattern only matches the line you mean
+> A too-broad pattern can delete the wrong fstab entry. Check the file before and
+> after, and keep the backup until you've confirmed the system still boots.
+
+### 4. Tear down the old disk's LVM
+
+```bash
+sudo lvremove -y /dev/oldvg/oldlv
+sudo vgremove -y oldvg
+sudo pvremove -y /dev/sdX        # wipes the LVM label off the disk
+```
+
+This is the point of no return for the old disk's data — which is why steps 2–3
+verified the copy first.
+
+### 5. Add the disk to the target VG and extend
+
+```bash
+sudo pvcreate -y /dev/sdX
+sudo vgextend myvg /dev/sdX
+sudo lvextend -l +100%FREE /dev/myvg/mylv
+```
+
+`lvs`/`vgs` should now show the LV grown to span both disks and `0` free extents.
+
+### 6. Grow the filesystem (online)
+
+```bash
+# ext4 — works while mounted
+sudo resize2fs /dev/mapper/myvg-mylv
+
+# XFS — grows online too, but takes the mountpoint, not the device
+sudo xfs_growfs /mountpoint
+```
+
+`resize2fs` is idempotent — if it gets interrupted, just run it again; it reports
+"Nothing to do!" once the filesystem already fills the LV.
+
+### 7. Verify
+
+```bash
+df -h /mountpoint     # should reflect the new larger size
+sudo pvs              # /dev/sdX now listed under myvg
+sudo vgs myvg         # two PVs, larger VSize
+```
+
+## Notes & Gotchas
+
+- **Online resize works for the volume being grown, not the one being removed.**
+  The disk you absorb must be unmounted and torn down; the destination LV stays
+  mounted throughout.
+- **`resize2fs` interruption is safe.** ext4 online resize is journaled; re-run it.
+- **macOS cruft on evacuated disks.** Trees touched by macOS often carry
+  `._*` AppleDouble files and `.DS_Store` — harmless to drop, but they inflate
+  file counts in `diff`/`rsync` output. Don't mistake them for real data.
+- **Check SMART on a disk you're promoting into a bigger role.** A disk with a
+  pending-sector history is riskier once it's in the critical path for a whole
+  multi-disk volume than it was holding a small isolated one.
+- **Mountpoint cleanup.** After the old disk is gone, its former mountpoint
+  directory may reappear (it was shadowed by the mount). `rmdir` it if empty.
+  Note `ls -A` exits `0` on an empty directory, so don't gate cleanup on its exit
+  status — test contents explicitly.
+
+## Related
+
+- [SnapRAID & MergerFS Storage Setup](snapraid-mergerfs-setup.md) — add redundancy/parity instead of a linear span
+- [mdadm — Rebuilding a RAID Array After Reinstall](mdadm-raid-rebuild.md)

SUMMARY.md

@@ -12,6 +12,7 @@ updated: 2026-06-19T10:05
     * [Bash Scripting Patterns](01-linux/shell-scripting/bash-scripting-patterns.md)
     * [SnapRAID & MergerFS Storage Setup](01-linux/storage/snapraid-mergerfs-setup.md)
     * [mdadm — Rebuilding a RAID Array After Reinstall](01-linux/storage/mdadm-raid-rebuild.md)
+    * [Growing an LVM Volume by Absorbing Another Disk](01-linux/storage/lvm-grow-volume-absorb-disk.md)
     * [Linux Distro Guide for Beginners](01-linux/distro-specific/linux-distro-guide-beginners.md)
     * [WSL2 Instance Migration to Fedora 43](01-linux/distro-specific/wsl2-instance-migration-fedora43.md)
     * [WSL2 Training Environment Rebuild](01-linux/distro-specific/wsl2-rebuild-fedora43-training-env.md)