How do I compress a folder while preserving file ownership
I have a docker server I want to backup. My deployment folder has very specific ownership and permissions to support my containers:
$ ls -lhaF /opt/docker
total 32K
drwxr-xr-x 7 devops devops 4.0K Aug 23 02:34 ./
drwxr-xr-x 6 root root 4.0K Aug 23 04:20 ../
drwxrwxr-x 2 devops devops 4.0K Aug 21 00:00 .certs/
drwxrwxr-x 2 devops devops 4.0K Aug 23 03:53 .scripts/
-rw-rw-r-- 1 devops devops 1.2K Aug 21 01:52 docker-compose.yml
drwxrwxr-x 4 1000 1000 4.0K Aug 21 02:05 minecraft/
drwxrwxr-x 4 devops devops 4.0K Aug 20 23:38 pihole/
drwx------ 19 70 70 4.0K Aug 19 01:31 postgres/
I then try to compress this folder using the following command. From what I've read preserving file permissions/ownership requires running tar as root/sudo:
$ sudo tar -czpf "/tmp/server-backup.tar.gz" --directory="/opt/docker" .
This command compresses the folder but inspecting the .tar.gz it shows that ownership of all folders are now root:
$ tar -tvf /tmp/server-backup.tar.gz
drwxr-xr-x root/root 0 2021-08-23 12:10 ./
drwxr-xr-x root/root 0 2021-08-23 12:10 ./minecraft/
-rw-r--r-- root/root 2 2021-08-23 12:10 ./minecraft/whitelist.json
-rw-r--r-- root/root 111 2021-08-23 12:10 ./minecraft/usercache.json
-rw-r--r-- root/root 1204 2021-08-23 12:10 ./minecraft/server.properties
-rw-r--r-- root/root 43626592 2021-08-23 12:10 ./minecraft/minecraft_server.1.17.1.jar
-rw-r--r-- root/root 68 2021-08-23 12:10 ./minecraft/eula.txt
-rw-r--r-- root/root 2 2021-08-23 12:10 ./minecraft/banned-players.json
-rw-r--r-- root/root 2 2021-08-23 12:10 ./minecraft/banned-ips.json
# -- Other minecraft files
drwxr-xr-x root/root 0 2021-08-23 12:10 ./.certs/
# -- Certs folder contents redacted
drwx------ root/root 0 2021-08-23 12:10 ./postgres/
drwx------ root/root 0 2021-08-23 12:10 ./postgres/pg_subtrans/
-rw------- root/root 8192 2021-08-23 12:10 ./postgres/pg_subtrans/0000
drwx------ root/root 0 2021-08-23 12:10 ./postgres/pg_multixact/
drwx------ root/root 0 2021-08-23 12:10 ./postgres/pg_multixact/offsets/
-rw------- root/root 8192 2021-08-23 12:10 ./postgres/pg_multixact/offsets/0000
drwx------ root/root 0 2021-08-23 12:10 ./postgres/pg_multixact/members/
-rw------- root/root 8192 2021-08-23 12:10 ./postgres/pg_multixact/members/0000
drwx------ root/root 0 2021-08-23 12:10 ./postgres/pg_xact/
-rw------- root/root 8192 2021-08-23 12:10 ./postgres/pg_xact/0000
# -- Other postgres files
drwxr-xr-x root/root 0 2021-08-23 12:10 ./pihole/
drwxr-xr-x root/root 0 2021-08-23 12:10 ./pihole/etc-pihole/
-rw-r--r-- root/root 0 2021-08-23 12:10 ./pihole/etc-pihole/custom.list
-rw-r--r-- root/root 5201920 2021-08-23 12:10 ./pihole/etc-pihole/gravity.db
-rw-r--r-- root/root 485 2021-08-23 12:10 ./pihole/etc-pihole/setupVars.conf
-rw-r--r-- root/root 0 2021-08-23 12:10 ./pihole/etc-pihole/setupVars.conf.update.bak
-rw-r--r-- root/root 1812161 2021-08-23 12:10 ./pihole/etc-pihole/list.1.raw.githubusercontent.com.domains
-rw-r--r-- root/root 73728 2021-08-23 12:10 ./pihole/etc-pihole/pihole-FTL.db
-rw-r--r-- root/root 0 2021-08-23 12:10 ./pihole/etc-pihole/pihole-FTL.conf
-rw-r--r-- root/root 37 2021-08-23 12:10 ./pihole/etc-pihole/local.list
-rw-r--r-- root/root 95 2021-08-23 12:10 ./pihole/etc-pihole/list.1.raw.githubusercontent.com.domains.sha1
-rw-r--r-- root/root 20 2021-08-23 12:10 ./pihole/etc-pihole/localbranches
drwxr-xr-x root/root 0 2021-08-23 12:10 ./pihole/etc-pihole/migration_backup/
-rw-r--r-- root/root 65 2021-08-23 12:10 ./pihole/etc-pihole/migration_backup/adlists.list
-rw-r--r-- root/root 618 2021-08-23 12:10 ./pihole/etc-pihole/dns-servers.conf
-rw-r--r-- root/root 20 2021-08-23 12:10 ./pihole/etc-pihole/GitHubVersions
-rw-r--r-- root/root 44 2021-08-23 12:10 ./pihole/etc-pihole/localversions
drwxr-xr-x root/root 0 2021-08-23 12:10 ./pihole/etc-dnsmasq.d/
-rw-r--r-- root/root 1475 2021-08-23 12:10 ./pihole/etc-dnsmasq.d/01-pihole.conf
drwxr-xr-x root/root 0 2021-08-23 12:10 ./.scripts/
-rwxr-xr-x root/root 1638 2021-08-23 12:10 ./.scripts/create-backup.sh
-rwxr-xr-x root/root 511 2021-08-23 12:10 ./.scripts/new-cert-pihole.sh
-rwxr-xr-x root/root 345 2021-08-23 12:10 ./.scripts/fix-permissions.sh
-rw-r--r-- root/root 1170 2021-08-23 12:10 ./docker-compose.yml
If I try to extract the .tar.gz file we can confirm that all ownership has been lost:
$ sudo mkdir /tmp/server-backup
$ sudo tar -xzpf /tmp/server-backup.tar.gz --directory=/tmp/server-backup
$ ls -lhaF /tmp/server-backup
total 32K
drwxr-xr-x 7 root root 4.0K Aug 23 12:10 ./
drwxrwxrwt 13 root root 4.0K Aug 23 12:16 ../
drwxr-xr-x 2 root root 4.0K Aug 23 12:10 .certs/
drwxr-xr-x 2 root root 4.0K Aug 23 12:10 .scripts/
-rw-r--r-- 1 root root 1.2K Aug 23 12:10 docker-compose.yml
drwxr-xr-x 4 root root 4.0K Aug 23 12:10 minecraft/
drwxr-xr-x 4 root root 4.0K Aug 23 12:10 pihole/
drwx------ 19 root root 4.0K Aug 23 12:10 postgres/
From what I've found, preserving ownership and permissions is supposed to be default behavior for tar. Is there something I'm missing here? I'd like to be able to backup the state of my server without messing up the delicate file ownership required by some of the docker containers I run.
System information:
$ lsb_release -d
Description: Ubuntu 20.04.3 LTS
$ uname -a
Linux rpi-1 5.4.0-1042-raspi #46-Ubuntu SMP PREEMPT Fri Jul 30 00:35:40 UTC 2021 aarch64 aarch64 aarch64 GNU/Linux
Apparently, tar isn't the culprit here. This was part of a larger script to backup my deployment folder. I was copying the folder before compressing to avoid read inconsistencies while the containers were still running. The script contained the following:
cp -R "/opt/docker" "/tmp/server-backup"
tar -czf "/tmp/server-backup.tar.gz" --directory="/tmp/server-backup" .
File ownership was being lost during the folder copy. The -p flag is required to preserve permissions/ownership on a folder copy. The correct command would have been this:
cp -Rp "/opt/docker" "/tmp/server-backup"
tar -czf "/tmp/server-backup.tar.gz" --directory="/tmp/server-backup" .