linux-disaster-recovery

name	linux-disaster-recovery
description	Use when recovering MySQL data, application files, configuration, boot state, or filesystems from a verified backup after loss or corruption; use linux-troubleshooting first when the fault may be recoverable without restore.
license	MIT
metadata	{"portable":true,"compatible_with":["claude-code","codex"],"author":"Peter Bamuhigire","author_url":"techguypeter.com","author_contact":"[phone]"}

Disaster Recovery

Distro support

Two-family skill. Backup/restore strategy and systemd rescue/emergency targets are identical; recovery-time tooling differs at a few critical points — get these wrong and a box won't boot. Body uses Debian/Ubuntu; substitute per this matrix.

Recovery concept	Debian/Ubuntu	RHEL family
Reinstall packages	apt install --reinstall	dnf reinstall
Regenerate GRUB	update-grub	grub2-mkconfig -o /boot/grub2/grub.cfg
GRUB config path	/boot/grub/grub.cfg	/boot/grub2/grub.cfg (UEFI: /boot/efi/EFI/<distro>/)
Rebuild initramfs	update-initramfs -u	dracut -f
Default root FS / repair	ext4 → e2fsck	xfs → xfs_repair (xfs can't shrink)
Restore networking	Netplan	NetworkManager/nmcli
Restore firewall	ufw	firewalld
Rescue target	systemctl rescue	identical

RHEL-family note: the two recovery actions that most often differ are GRUB regeneration (grub2-mkconfig, not update-grub) and initramfs rebuild (dracut -f, not update-initramfs). Root is usually XFS — use xfs_repair, and remember XFS cannot be shrunk. See docs/multi-distro/plan.md. In sk-* scripts use the common.sh package primitives.

Use when

• Data has been lost, corrupted, or overwritten and a restore may be required.
• You need to recover databases, application files, or config snapshots from backups.
• You need an emergency recovery checklist during a production incident.

Do not use when

• The problem is only a service outage or bad config that can be fixed in place; use linux-service-management or linux-troubleshooting.
• The task is a routine backup review rather than an actual restore path.
• The task is creating backups — building rsync/tar archives, incremental snapshots, or filesystem (LVM/ZFS/Btrfs) snapshots. That now lives in the 13-backup-and-archiving category: linux-rsync-sync (offsite/incremental rsync), linux-archive-integrity (tar create + verify), and linux-filesystem-snapshots (LVM/ZFS/Btrfs). This skill stays focused on restore and emergency recovery.

Required Inputs

Artefact	Source	Required?	If absent
Incident timeline, affected scope, and recovery objective	Incident commander/data owner	yes	Stop; do not choose a restore point
Backup catalogue, timestamp, checksum, and encryption access	Backup system/secret provider	yes	Do not restore or claim recoverability
Restore authority, target, and outage window	Change/data owner	yes for mutation	Produce a recovery plan only
Validation queries/files and rollback path	Application owner	yes	Stop before overwriting live state

Capability Contract

Read/search access may assess backups and recovery options. Decryption, filesystem repair, database replacement, bootloader/initramfs work, service stops, and destructive restores require explicit authority, protected credentials, and a recovery target. Never overwrite the sole surviving copy.

Degraded Mode

Fallback when restore verification is unavailable: report the narrowest recoverable scope and blocking gap. Missing checksums, keys, isolated space, capacity, or application validation mean the recovery point has not passed.

Decision Rules

Condition	Action	Failure avoided
Fault may be configuration/service-only	Troubleshoot before restore	Unnecessary data rollback
Latest backup may contain corruption	Select last verified pre-incident point	Restoring bad state
Partial restore satisfies objective	Restore smallest isolated scope first	Excessive data loss/downtime
Source and target filesystem differ	Use family/filesystem-specific recovery path	Unbootable or damaged host

Workflow

Before selecting a restore point, use the two-family validation and recovery reference. Qualify the backup and target filesystem, test the smallest isolated restore, preserve the current target, and record application-level validation. If a recovery check is unavailable, report the narrowest recoverable scope and keep the action open; do not treat a successful file extraction as proof that the service or data is recovered.

1. Stabilise the incident, preserve current state, and confirm restore is necessary.
2. Define RPO/RTO, exact scope, target, authority, and rollback; stop if any required decision is absent.
3. Inventory candidate backups and verify timestamp, checksum, decryptability, and pre-incident status.
4. Test the smallest suitable restore in isolation and run application validation.
5. Confirm destructive impact, back up current target, execute the authorised restore, and record commands.
6. Validate data/service/access; on failure recover the pre-restore target and keep the incident open.

Evidence Produced

Artefact	Acceptance
Backup qualification	Shows source, timestamp, checksum, decrypt test, and incident relation
Restore execution record	Includes approval, target backup, commands, before-state backup, and timestamps
Recovery validation	Proves application queries/files, service health, access, and residual data gap

Quality standards

• Restore the smallest correct scope first when possible.
• Use timestamps and incident facts to choose the backup, not guesswork.
• Verification after restore is mandatory.

Anti-patterns

• Restoring over live data without confirmation. Fix: record authority, target, impact, and before-state backup.
• Choosing the latest backup blindly. Fix: select a verified point before the incident/corruption.
• Ending after the restore command. Fix: run application, integrity, service, and access checks.
• Testing decryption for the first time during production restore. Fix: qualify the backup in isolation first.
• Repairing the wrong filesystem with family assumptions. Fix: detect filesystem and use its supported tooling.
• Overwriting the only surviving copy. Fix: restore into isolated space or clone current state first.

Outputs

Artefact	Consumer	Acceptance condition
Recovery plan	Incident commander	Names RPO/RTO, restore point, scope, authority, validation, and rollback
Restored service/data	Application owner	Meets defined validation without destroying the source backup
Residual-loss statement	Data/risk owner	Quantifies time/data gap and unresolved controls

Worked Example

A table was corrupted at 10:20 EAT. Verify and decrypt the 10:00 database backup into an isolated database, validate row counts and application queries, then restore only the affected database after approval. Keep a dump of the damaged live database for rollback and investigation.

Book-derived additions

For a mission-aware NGO recovery plan, load ../../07-security-and-hardening/linux-ngo-cyber-resilience/SKILL.md and retain evidence preservation, staged restoration, integrity checks, and credential rotation.

References

• references/backup-strategy.md
• references/restore-procedures.md
• ../../docs/continuous-improvement/two-family-validation-and-recovery.md
• ../../docs/continuous-improvement/incident-learning-standard.md

This skill is self-contained. Every command below works on a stock Debian/Ubuntu or RHEL-family server (substitute per the Distro support matrix above). The sk-* scripts in the Optional fast path section at the bottom are convenience wrappers — never required.

Always confirm before restoring. A restore overwrites existing data. Never start a restore without typing the full word yes at the prompt, even in non-interactive mode.

---

Step 1: Assess First

# Is this a service crash (restart only) or actual data loss?
sudo systemctl status nginx mysql postgresql php8.3-fpm

# When did it happen?
sudo journalctl --since "2 hours ago" | grep -iE "error|fail|crash" | head -20

Service crash → restart it (linux-service-management), no restore needed. Data loss/corruption → proceed below.

Step 2: Find The Right Backup

# Local backups (7-day retention)
ls -lth ~/backups/mysql/*.gpg 2>/dev/null | head -10

# Google Drive (3-day retention for MySQL)
rclone ls gdrive:<backup-folder> 2>/dev/null | sort | tail -10

# If rclone token expired:
rclone config reconnect gdrive:

Choose the backup closest to before the incident.

Step 3: Restore

Full restore procedure (decrypt → extract → import): See references/restore-procedures.md.

The procedure, condensed:

# Decrypt (enter passphrase when prompted)
gpg --decrypt backup.sql.gz.gpg > backup.sql.gz

# Inspect size and sanity
gunzip -l backup.sql.gz
zcat backup.sql.gz | head -20

# Stop the service that writes to the DB
sudo systemctl stop nginx apache2 php8.3-fpm

# Restore (confirm first!)
zcat backup.sql.gz | mysql -u root -p <database>

# Restart
sudo systemctl start php8.3-fpm apache2 nginx

Emergency Checklist

# 1. Stop affected service to prevent further damage
sudo systemctl stop <service>

# 2. Find best backup (Step 2 above)

# 3. Decrypt → restore → verify (references/restore-procedures.md)

# 4. Restart all services
sudo systemctl start nginx mysql php8.3-fpm apache2

# 5. Re-run security audit
sudo bash ~/.claude/skills/scripts/server-audit.sh

# 6. Clean up
rm -rf ~/restore/

Demo/Dev Reset (Git-Tracked SQL Dump Pattern)

Some apps ship a git-tracked SQL dump as the demo DB source of truth. A reset script drops and recreates from that dump:

ls /usr/local/bin/reset-*           # find available reset scripts
sudo reset-<app>-from-git           # requires typing YES
ls /var/backups/<app>/              # safety backup always created first

---

Optional fast path (when sk-* scripts are installed)

Running sudo install-skills-bin linux-disaster-recovery installs wrappers for the above:

Task	Fast-path script
Verify last backup is usable	sudo sk-backup-verify
Guided restore (pick backup, preview, confirm)	sudo sk-restore-wizard
MySQL restore from a specific file	sudo sk-mysql-restore --file <path>
PostgreSQL restore	sudo sk-postgres-restore --file <path>
Site file restore	sudo sk-site-restore --backup <path> --target <dir>
Maintenance mode on/off	sudo sk-emergency-mode on|off

These are optional wrappers around the commands above.

Demo/Dev Reset (Git-Tracked SQL Dump Pattern)

Some apps ship a git-tracked SQL dump as the demo DB source of truth. A reset script drops and recreates from that dump:

ls /usr/local/bin/reset-*           # find available reset scripts
sudo reset-<app>-from-git           # requires typing YES
ls /var/backups/<app>/              # safety backup always created first

Scripts

This skill installs the following scripts to /usr/local/bin/. To install:

sudo install-skills-bin linux-disaster-recovery

Script	Source	Core?	Purpose
sk-backup-verify	scripts/sk-backup-verify.sh	yes	Verify last backup age, integrity (tar/gpg check), remote copy reachable via rclone.
sk-mysql-backup	scripts/sk-mysql-backup.sh	yes	Dump all databases with gzip + gpg + rclone upload; rotate local and remote. Refactored to source common.sh and honor standard flags.
sk-mysql-restore	scripts/sk-mysql-restore.sh	no	Guided restore: list backups, pick, download, decrypt, show sizes, confirm, restore.
sk-postgres-backup	scripts/sk-postgres-backup.sh	no	pg_dump + compression + gpg + rclone, per database or all, with rotation.
sk-postgres-restore	scripts/sk-postgres-restore.sh	no	Guided PostgreSQL restore from backup file or remote.
sk-site-backup	scripts/sk-site-backup.sh	no	Tar a full site directory, exclude cache/node_modules, gpg, upload via rclone.
sk-site-restore	scripts/sk-site-restore.sh	no	Restore a site backup to original path with permission repair.
sk-config-snapshot	scripts/sk-config-snapshot.sh	no	Snapshot /etc/ (and other declared dirs) to a git-tracked archive; diff against previous.
sk-restore-wizard	scripts/sk-restore-wizard.sh	no	Interactive guided restore: pick backup set, pick target, preview, confirm, execute.
sk-emergency-mode	scripts/sk-emergency-mode.sh	no	Toggle maintenance mode: drop Nginx to 503 page, stop non-essential services, show live status.