check the root filesystem is actually using the whole drive
New first section, before anything else that changes the machine, because the
swapfile and the ballast both size themselves from free disk.
Ubuntu Server's installer on its defaults gives the root logical volume a fixed
size and leaves the rest of the drive as unallocated extents in the volume group.
On a 2TB disk that is a ~100G root with nothing to indicate a problem: lsblk
shows the whole drive, df shows 100G, and the two are never seen side by side
until the day it fills. Growing a virtual disk at a provider leaves the same
shape one layer down, and so does resizing a partition without telling the
filesystem inside it.
Three layers, any of which can be the short one, so all three are measured and
printed together:
drive: 76.3GB /dev/sda
volume: 76.1GB /dev/sda1
filesystem: 76.1GB ext4, mounted at /
Seeing them in one place is most of the value. The fix is then whichever layer is
short: lvextend for free extents, growpart for a partition that stops early
(followed by pvresize and lvextend when LVM is in the way), or resize2fs alone
when only the filesystem is behind.
Only ever grows. Nothing here shrinks, creates or deletes a partition, and ext4,
xfs and btrfs all grow while mounted — so no unmount, no reboot, and a failure
part-way leaves a smaller filesystem on a larger container, which is the state it
started in.
growpart is the authority on whether a partition can move — it exits 1 with
NOCHANGE when the partition already reaches the end — but it comes from
cloud-guest-utils, which is not on every image. Installing a package purely to
ask a question is too eager, so plain arithmetic on the device sizes decides
whether it is even worth looking, and only then is growpart fetched.
A gigabyte of slack before anything is reported: a filesystem is always slightly
smaller than its container, and reporting journal and reserved-block overhead as
reclaimable space would make this section cry wolf on every machine.
Verified on this host: plain ext4 partition filling its disk, correctly reports
nothing to reclaim, and every helper returns the right device and size.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
This commit is contained in:
Claude Opus 5
@@ -24,6 +24,8 @@ source "$SCRIPT_DIR/lib/packages.sh"
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source "$SCRIPT_DIR/lib/tools.sh"
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# shellcheck source=lib/system.sh
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source "$SCRIPT_DIR/lib/system.sh"
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# shellcheck source=lib/disk.sh
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source "$SCRIPT_DIR/lib/disk.sh"
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# Trap errors with context. Installed here rather than in lib/base.sh, because
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# that file is definitions only and a trap is a side effect on whoever sources it.
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@@ -85,7 +87,102 @@ info "Refreshing the package index..."
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pkg_refresh >/dev/null
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# =============================================================================
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# 2. System update
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# 2. Disk space
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# =============================================================================
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#
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# First of the sections that change anything, because everything after it sizes
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# itself from free disk — the swapfile and the ballast both.
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step "Disk space"
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if ! skip; then
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ROOT_DEV="$(root_device)"
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ROOT_DISK="$(parent_disk "$ROOT_DEV")"
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ROOT_PART="$(backing_partition "$ROOT_DEV" || true)"
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DISK_B="$(dev_bytes "$ROOT_DISK")"
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CONT_B="$(dev_bytes "$ROOT_DEV")"
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FS_B="$(fs_bytes "$ROOT_DEV")"
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VG_FREE_B="$(vg_free_bytes)"
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# A filesystem is always a little smaller than the thing holding it —
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# metadata, journal, reserved blocks. Only a real gap is worth reporting.
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SLACK=$((1024 * 1024 * 1024))
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echo ""
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info "Disk space — whether the root filesystem is actually using the whole drive"
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echo " Ubuntu's installer, left on its defaults, gives the root volume a"
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echo " fixed size and leaves the rest of the drive unallocated. On a 2TB"
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echo " disk that is a 100G root and no sign anything is wrong: lsblk shows"
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echo " the whole drive, df shows 100G, and the two are never seen together"
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echo " until the day it fills up. Growing a virtual disk at the provider"
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echo " leaves the same shape."
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echo ""
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echo " drive: $(human_bytes "$DISK_B") ${ROOT_DISK}"
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echo " volume: $(human_bytes "$CONT_B") ${ROOT_DEV}"
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echo " filesystem: $(human_bytes "$FS_B") $(root_fstype), mounted at /"
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((VG_FREE_B > SLACK)) && echo " unused in LVM: $(human_bytes "$VG_FREE_B")"
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# growpart is the authority on whether a partition can move, but installing a
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# package just to ask is too eager — the arithmetic decides whether it is even
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# worth looking.
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MIGHT_GROW=false
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((DISK_B - CONT_B > SLACK)) && MIGHT_GROW=true
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[[ -n "$ROOT_PART" ]] && $MIGHT_GROW && ensure_growpart
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if ((VG_FREE_B > SLACK)); then
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echo ""
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echo " $(human_bytes "$VG_FREE_B") is sitting unallocated in the volume group"
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echo " the fix is lvextend, then growing the filesystem into it — both online"
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if confirm "Use it?"; then
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grow_lv && grow_fs
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ok "root filesystem is now $(human_bytes "$(fs_bytes "$ROOT_DEV")")"
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SUMMARY+=("Disk: reclaimed $(human_bytes "$VG_FREE_B") from the volume group")
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else
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warn "skipped by request"
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SUMMARY+=("Disk: SKIPPED — $(human_bytes "$VG_FREE_B") left unallocated")
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fi
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elif [[ -n "$ROOT_PART" ]] && partition_can_grow "$ROOT_PART"; then
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echo ""
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echo " the partition stops short of the end of the drive"
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echo " this is the one step that edits the partition table — it only ever"
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echo " moves the end of ${ROOT_PART} outwards, and never touches another one"
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if confirm "Extend it?"; then
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grow_partition "$ROOT_PART"
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if root_is_lvm; then
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grow_pv "$ROOT_PART"
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grow_lv
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fi
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grow_fs
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ok "root filesystem is now $(human_bytes "$(fs_bytes "$ROOT_DEV")")"
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SUMMARY+=("Disk: partition extended, filesystem now $(human_bytes "$(fs_bytes "$ROOT_DEV")")")
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else
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warn "skipped by request"
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SUMMARY+=("Disk: SKIPPED — partition left short of the drive")
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fi
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elif ((FS_B > 0 && CONT_B - FS_B > SLACK)); then
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echo ""
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echo " the filesystem is smaller than the volume holding it"
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if confirm "Grow it?"; then
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grow_fs
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ok "root filesystem is now $(human_bytes "$(fs_bytes "$ROOT_DEV")")"
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SUMMARY+=("Disk: filesystem grown to $(human_bytes "$(fs_bytes "$ROOT_DEV")")")
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else
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warn "skipped by request"
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SUMMARY+=("Disk: SKIPPED — filesystem left short of its volume")
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fi
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else
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echo ""
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echo " the whole drive is in use, nothing to reclaim"
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SUMMARY+=("Disk: already using the whole drive")
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fi
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step_ok
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fi
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# =============================================================================
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# 3. System update
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# =============================================================================
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#
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# Its own section because it is the only thing in the script that moves versions
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@@ -125,7 +222,7 @@ if ! skip; then
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fi
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# =============================================================================
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# 3. Core utils
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# 4. Core utils
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# =============================================================================
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#
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# What the distribution provides: the six this script would break without, and
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@@ -140,7 +237,7 @@ if ! skip; then
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fi
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# =============================================================================
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# 4. Command-line tools
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# 5. Command-line tools
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# =============================================================================
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#
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# A different thing from core utils, and kept apart from them: upstream binaries
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@@ -158,7 +255,7 @@ fi
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# =============================================================================
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# 5. Locale
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# 6. Locale
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# =============================================================================
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#
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# LOCALE in the environment overrides the default.
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@@ -196,7 +293,7 @@ if ! skip; then
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fi
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# =============================================================================
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# 6. Timezone
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# 7. Timezone
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# =============================================================================
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#
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# TIMEZONE in the environment answers the prompt ahead of time.
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@@ -262,7 +359,7 @@ if ! skip; then
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fi
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# =============================================================================
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# 7. Swap
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# 8. Swap
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# =============================================================================
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#
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# Disk the kernel can park cold pages on when RAM fills, so a spike costs
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@@ -316,7 +413,7 @@ if ! skip; then
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fi
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# =============================================================================
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# 8. Emergency disk ballast
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# 9. Emergency disk ballast
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# =============================================================================
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#
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# Always offered, whatever the role — the role only decides which way the
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@@ -359,7 +456,7 @@ if ! skip; then
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fi
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# =============================================================================
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# 9. earlyoom
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# 10. earlyoom
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# =============================================================================
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step "earlyoom"
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@@ -394,7 +491,7 @@ if ! skip; then
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fi
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# =============================================================================
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# 10. inotify watch limit
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# 11. inotify watch limit
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# =============================================================================
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step "inotify watch limit"
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@@ -447,7 +544,7 @@ fi
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# =============================================================================
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# 23. Summary
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# 12. Summary
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# =============================================================================
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echo ""
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Reference in New Issue
Block a user