Issue Signatures couldn't be verified because the public key is not available

[cartapps]

Server operating system version

Ubuntu 26.04.1 LTS

Plesk version and microupdate number

Plesk Obsidian v18.0.82_build1800261023.10 os_Ubuntu 26.04

There are multiple warnings while updating ubuntu and plesk. can u check into this?

Error: Unable to get packages list: 2026-10-27 21:49:40 INFO: pum is called with arguments: ['--list', '--repo-info', '--json'] /usr/lib/python3/dist-packages/apt/cache.py:565: Warning: W:An error occurred during the signature verification. The repository is not updated and the previous index files will be used. OpenPGP signature verification failed: http://autoinstall.plesk.com/WATCHDOG_3.1.0 resolute InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY E9299045CE550E57, W:Target Packages (all/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list.d/plesk.list:3 and /etc/apt/sources.list.d/plesk.sources:2, W:Target Packages (all/binary-all/Packages) is configured multiple times in /etc/apt/sources.list.d/plesk.list:3 and /etc/apt/sources.list.d/plesk.sources:2, W:Target Translations (all/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list.d/plesk.list:3 and /etc/apt/sources.list.d/plesk.sources:2, W:Target DEP-11 (all/dep11/Components-amd64.yml) is configured multiple times in /etc/apt/sources.list.d/plesk.list:3 and /etc/apt/sources.list.d/plesk.sources:2, W:Target DEP-11 (all/dep11/Components-all.yml) is configured multiple times in /etc/apt/sources.list.d/plesk.list:3 and /etc/apt/sources.list.d/plesk.sources:2, W:Target Packages (all/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list.d/plesk.list:4 and /etc/apt/sources.list.d/plesk.sources:3, W:Target Packages (all/binary-all/Packages) is configured multiple times in /etc/apt/sources.list.d/plesk.list:4 and /etc/apt/sources.list.d/plesk.sources:3, W:Target Translations (all/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list.d/plesk.list:4 and /etc/apt/sources.list.d/plesk.sources:3, W:Target DEP-11 (all/dep11/Components-amd64.yml) is configured multiple times in /etc/apt/sources.list.d/plesk.list:4 and /etc/apt/sources.list.d/plesk.sources:3, W:Target DEP-11 (all/dep11/Components-all.yml) is configured multiple times in /etc/apt/sources.list.d/plesk.list:4 and /etc/apt/sources.list.d/plesk.sources:3, W:Target Packages (all/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list.d/plesk.list:5 and /etc/apt/sources.list.d/plesk.sources:4, W:Target Packages (all/binary-all/Packages) is configured multiple times in /etc/apt/sources.list.d/plesk.list:5 and /etc/apt/sources.list.d/plesk.sources:4, W:Target Translations (all/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list.d/plesk.list:5 and /etc/apt/sources.list.d/plesk.sources:4, W:Target DEP-11 (all/dep11/Components-amd64.yml) is configured multiple times in /etc/apt/sources.list.d/plesk.list:5 and /etc/apt/sources.list.d/plesk.sources:4, W:Target DEP-11 (all/dep11/Components-all.yml) is configured multiple times in /etc/apt/sources.list.d/plesk.list:5 and /etc/apt/sources.list.d/plesk.sources:4, W:An error occurred during the signature verification. The repository is not updated and the previous index files will be used. OpenPGP signature verification failed: http://autoinstall.plesk.com/pool/PSA_18.0.81_19954 resolute InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY E9299045CE550E57, W:Failed to fetch http://autoinstall.plesk.com/WATCHDOG_3.1.0/dists/resolute/InRelease The following signatures couldn't be verified because the public key is not available: NO_PUBKEY E9299045CE550E57, W:Failed to fetch http://autoinstall.plesk.com/pool/PSA_18.0.81_19954/dists/resolute/InRelease The following signatures couldn't be verified because the public key is not available: NO_PUBKEY E9299045CE550E57, W:Some index files failed to download. They have been ignored, or old ones used instead. res = self._cache.update(fetch_progress, slist, pulse_interval) 2026-10-27 21:49:42 ERROR: Apt cache fetch failed. Try to run the `apt-get update` command. 2026-10-27 21:49:42 ERROR: 2026-10-27 21:49:42 ERROR: Exited with returncode 1.

 

[cartapps]

SSH Warnings in the attachments --

 

[Sebahat.hadzhi]

Hi, @cartapps . Please run the following command with the root user to attempt to restore the GPG Key:

curl -sS http://autoinstall.plesk.com/plesk.gpg | gpg --dearmor >> /etc/apt/keyrings/plesk.gpg

Thanks in advance. Let us know if the issue still continues afterward.

 

[cartapps]

Hi, @cartapps . Please run the following command with the root user to attempt to restore the GPG Key:

curl -sS http://autoinstall.plesk.com/plesk.gpg | gpg --dearmor >> /etc/apt/keyrings/plesk.gpg

Thanks in advance. Let us know if the issue still continues afterward.

I tried that already and its not working, also there are other warnings too.

 

[learning_curve]

@cartapps

Server operating system version: Ubuntu 26.04.1 LTS                                                                                                           
Plesk version and microupdate number: Plesk Obsidian v18.0.82_build1800261023.10 os_Ubuntu 26.04

"There are multiple warnings while updating ubuntu and plesk. can u check into this?"

We have the same server OS and same Plesk release, but with zero issues.
There's a very clear "clue" in your PDF that your own data within /etc/apt/sources.list.d/ is misconfigured for many packages.
That's not a Plesk error, it's your own config e.g. "...is configured multiple times in /etc/apt/sources.list.d/plesk.list:3 and /etc/apt/sources.list.d/plesk.sources..."

FWIW: "...Ubuntu 26.04 LTS uses deb822  .sources  files for APT repository configuration instead of the older one-line  .list  format. This changes how repositories are described, not how packages are installed. The default switch began with Ubuntu 24.04 LTS but Ubuntu 26.04 continues it..."

 

[swemp]

Hello there!
I have the same problems here.
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. OpenPGP signature verification failed: Index of /WATCHDOG_3.1.0 resolute InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY E9299045CE550E57
W: Target Packages (all/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list.d/plesk.list:3 and /etc/apt/sources.list.d/plesk.sources:4
W: Target Packages (all/binary-all/Packages) is configured multiple times in /etc/apt/sources.list.d/plesk.list:3 and /etc/apt/sources.list.d/plesk.sources:4
W: Target Translations (all/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list.d/plesk.list:3 and /etc/apt/sources.list.d/plesk.sources:4
W: Target DEP-11 (all/dep11/Components-amd64.yml) is configured multiple times in /etc/apt/sources.list.d/plesk.list:3 and /etc/apt/sources.list.d/plesk.sources:4
W: Target DEP-11 (all/dep11/Components-all.yml) is configured multiple times in /etc/apt/sources.list.d/plesk.list:3 and /etc/apt/sources.list.d/plesk.sources:4
W: Target CNF (all/cnf/Commands-amd64) is configured multiple times in /etc/apt/sources.list.d/plesk.list:3 and /etc/apt/sources.list.d/plesk.sources:4
W: Target CNF (all/cnf/Commands-all) is configured multiple times in /etc/apt/sources.list.d/plesk.list:3 and /etc/apt/sources.list.d/plesk.sources:4
W: Target Packages (all/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list.d/plesk.list:4 and /etc/apt/sources.list.d/plesk.sources:5
W: Target Packages (all/binary-all/Packages) is configured multiple times in /etc/apt/sources.list.d/plesk.list:4 and /etc/apt/sources.list.d/plesk.sources:5
W: Target Translations (all/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list.d/plesk.list:4 and /etc/apt/sources.list.d/plesk.sources:5
W: Target DEP-11 (all/dep11/Components-amd64.yml) is configured multiple times in /etc/apt/sources.list.d/plesk.list:4 and /etc/apt/sources.list.d/plesk.sources:5
W: Target DEP-11 (all/dep11/Components-all.yml) is configured multiple times in /etc/apt/sources.list.d/plesk.list:4 and /etc/apt/sources.list.d/plesk.sources:5
W: Target CNF (all/cnf/Commands-amd64) is configured multiple times in /etc/apt/sources.list.d/plesk.list:4 and /etc/apt/sources.list.d/plesk.sources:5
W: Target CNF (all/cnf/Commands-all) is configured multiple times in /etc/apt/sources.list.d/plesk.list:4 and /etc/apt/sources.list.d/plesk.sources:5
W: Target Packages (all/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list.d/plesk.list:5 and /etc/apt/sources.list.d/plesk.sources:6
W: Target Packages (all/binary-all/Packages) is configured multiple times in /etc/apt/sources.list.d/plesk.list:5 and /etc/apt/sources.list.d/plesk.sources:6
W: Target Translations (all/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list.d/plesk.list:5 and /etc/apt/sources.list.d/plesk.sources:6
W: Target DEP-11 (all/dep11/Components-amd64.yml) is configured multiple times in /etc/apt/sources.list.d/plesk.list:5 and /etc/apt/sources.list.d/plesk.sources:6
W: Target DEP-11 (all/dep11/Components-all.yml) is configured multiple times in /etc/apt/sources.list.d/plesk.list:5 and /etc/apt/sources.list.d/plesk.sources:6
W: Target CNF (all/cnf/Commands-amd64) is configured multiple times in /etc/apt/sources.list.d/plesk.list:5 and /etc/apt/sources.list.d/plesk.sources:6
W: Target CNF (all/cnf/Commands-all) is configured multiple times in /etc/apt/sources.list.d/plesk.list:5 and /etc/apt/sources.list.d/plesk.sources:6
W: Failed to fetch http://autoinstall.plesk.com/WATCHDOG_3.1.0/dists/resolute/InRelease The following signatures couldn't be verified because the public key is not available: NO_PUBKEY E9299045CE550E57
W: Some index files failed to download. They have been ignored, or old ones used instead.
W: Target Packages (all/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list.d/plesk.list:3 and /etc/apt/sources.list.d/plesk.sources:4
W: Target Packages (all/binary-all/Packages) is configured multiple times in /etc/apt/sources.list.d/plesk.list:3 and /etc/apt/sources.list.d/plesk.sources:4
W: Target Translations (all/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list.d/plesk.list:3 and /etc/apt/sources.list.d/plesk.sources:4
W: Target DEP-11 (all/dep11/Components-amd64.yml) is configured multiple times in /etc/apt/sources.list.d/plesk.list:3 and /etc/apt/sources.list.d/plesk.sources:4
W: Target DEP-11 (all/dep11/Components-all.yml) is configured multiple times in /etc/apt/sources.list.d/plesk.list:3 and /etc/apt/sources.list.d/plesk.sources:4
W: Target CNF (all/cnf/Commands-amd64) is configured multiple times in /etc/apt/sources.list.d/plesk.list:3 and /etc/apt/sources.list.d/plesk.sources:4
W: Target CNF (all/cnf/Commands-all) is configured multiple times in /etc/apt/sources.list.d/plesk.list:3 and /etc/apt/sources.list.d/plesk.sources:4
W: Target Packages (all/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list.d/plesk.list:4 and /etc/apt/sources.list.d/plesk.sources:5
W: Target Packages (all/binary-all/Packages) is configured multiple times in /etc/apt/sources.list.d/plesk.list:4 and /etc/apt/sources.list.d/plesk.sources:5
W: Target Translations (all/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list.d/plesk.list:4 and /etc/apt/sources.list.d/plesk.sources:5
W: Target DEP-11 (all/dep11/Components-amd64.yml) is configured multiple times in /etc/apt/sources.list.d/plesk.list:4 and /etc/apt/sources.list.d/plesk.sources:5
W: Target DEP-11 (all/dep11/Components-all.yml) is configured multiple times in /etc/apt/sources.list.d/plesk.list:4 and /etc/apt/sources.list.d/plesk.sources:5
W: Target CNF (all/cnf/Commands-amd64) is configured multiple times in /etc/apt/sources.list.d/plesk.list:4 and /etc/apt/sources.list.d/plesk.sources:5
W: Target CNF (all/cnf/Commands-all) is configured multiple times in /etc/apt/sources.list.d/plesk.list:4 and /etc/apt/sources.list.d/plesk.sources:5
W: Target Packages (all/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list.d/plesk.list:5 and /etc/apt/sources.list.d/plesk.sources:6
W: Target Packages (all/binary-all/Packages) is configured multiple times in /etc/apt/sources.list.d/plesk.list:5 and /etc/apt/sources.list.d/plesk.sources:6
W: Target Translations (all/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list.d/plesk.list:5 and /etc/apt/sources.list.d/plesk.sources:6
W: Target DEP-11 (all/dep11/Components-amd64.yml) is configured multiple times in /etc/apt/sources.list.d/plesk.list:5 and /etc/apt/sources.list.d/plesk.sources:6
W: Target DEP-11 (all/dep11/Components-all.yml) is configured multiple times in /etc/apt/sources.list.d/plesk.list:5 and /etc/apt/sources.list.d/plesk.sources:6
W: Target CNF (all/cnf/Commands-amd64) is configured multiple times in /etc/apt/sources.list.d/plesk.list:5 and /etc/apt/sources.list.d/plesk.sources:6
W: Target CNF (all/cnf/Commands-all) is configured multiple times in /etc/apt/sources.list.d/plesk.list:5 and /etc/apt/sources.list.d/plesk.sources:6
N: Missing Signed-By in the sources.list(5) entry for 'Index of /alt-common/deb/ubuntu/26.04/stable/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-1/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-2/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-3/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-4/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-5/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-6/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-7/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-8/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-9/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-10/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-11/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-12/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /imunify360/ubuntu/26.04/'

Regards,

Martin

 

[tessa67]

Hi @cartapps,

Looks like two separate things are happening here:

1. Duplicate repo entries (the wall of “configured multiple times” warnings)
The same Plesk repos are defined twice: once in the old one-line plesk.list (lines 3-5) and once in the newer deb822 plesk.sources (lines 2-4). Ubuntu 26.04 uses the .sources format, so one of those files is a leftover. That’s just noise, not a real error.

2. The actual error (NO_PUBKEY E9299045CE550E57)
In your apt update output, only two repos fail: WATCHDOG_3.1.0 and pool/PSA_18.0.81_19954. The current ones (WATCHDOG_3.3.0, PSA_18.0.82_20288, PHP, Grafana) are fine. So these look like old entries from a previous Plesk version that are still in your config and can’t be verified with the key you have. That would also explain why re-importing the GPG key didn’t help: the old entries probably reference a different keyring or no key at all. That last part is a guess though, the logs don’t show it.

The “Missing Signed-By” notices for Imunify360/TuxCare are just notices, you can ignore them.
Please post the output of these so we can see which file the two old entries live in:

ls -l /etc/apt/sources.list.d/
cat /etc/apt/sources.list.d/plesk.list
cat /etc/apt/sources.list.d/plesk.sources
ls -l /etc/apt/keyrings/

Then it should be a quick fix, most likely removing the stale entries / the duplicate plesk.list. Don’t delete anything yet though, let’s look at the files first. Also worth noting: your original >> command appends to the keyring file, so if you ran it several times, it’s best not to repeat it.

Regards
Tessa

 

[swemp]

Here are the outputs:
# ls -l /etc/apt/sources.list.d/
total 64
-rw-r--r-- 1 root root 191 Oct 8 16:11 50sw_autoinstaller.list.bak
-rw-r--r-- 1 root root 142 Oct 8 16:14 50sw_autoinstaller.sources
-rw-r--r-- 1 root root 216 Oct 8 04:54 alt-common-els.list.bak
-rw-r--r-- 1 root root 128 Oct 8 16:14 alt-common-els.sources
-rw-r--r-- 1 root root 1083 May 20 18:35 imunify-rollout-bypass.list.disabled
-rw-r--r-- 1 root root 999 May 20 18:35 imunify-rollout.list.bak
-rw-r--r-- 1 root root 1394 Oct 8 16:14 imunify-rollout.sources
-rw-r--r-- 1 root root 95 May 20 18:35 imunify360.list.bak
-rw-r--r-- 1 root root 127 Oct 8 16:14 imunify360.sources
-rw-r--r-- 1 root root 125 Oct 26 18:36 plesk-ext-watchdog.list
-rw-r--r-- 1 root root 125 Oct 8 05:02 plesk-ext-watchdog.list.bak
-rw-r--r-- 1 root root 147 Oct 8 16:14 plesk-ext-watchdog.sources
-rw-r--r-- 1 root root 451 Oct 28 06:26 plesk.list
-rw-r--r-- 1 root root 748 Oct 8 16:11 plesk.list.bak
-rw-r--r-- 1 root root 925 Oct 13 10:55 plesk.sources
-rw-r--r-- 1 root root 3018 Oct 8 04:44 ubuntu.sources
root@friendly-gauss:/home/administrator# cat /etc/apt/sources.list.d/plesk.list
## Persistent repositories for Plesk Products.
deb [signed-by=/etc/apt/keyrings/plesk.gpg] http://autoinstall.plesk.com/pool/PS A_18.0.81_20292/ resolute extras
deb [signed-by=/etc/apt/keyrings/plesk.gpg] http://autoinstall.plesk.com/PHP83_1 7/ resolute all
deb [signed-by=/etc/apt/keyrings/plesk.gpg] http://autoinstall.plesk.com/PHP84_1 7/ resolute all
deb [signed-by=/etc/apt/keyrings/plesk.gpg] http://autoinstall.plesk.com/PHP85_1 root@friendly-gauss:/home/administrator# cat /etc/apt/sources.list.d/plesk.sourc es.d/plesk.sources
Types: deb
URIs: Index of /pool/PSA_18.0.81_20048
Suites: resolute
Components: extras
Signed-By: /etc/apt/keyrings/plesk.gpg

Types: deb
URIs: Index of /PHP81_17
Suites: resolute
Components: all
Signed-By: /etc/apt/keyrings/plesk.gpg

Types: deb
URIs: Index of /PHP82_17
Suites: resolute
Components: all
Signed-By: /etc/apt/keyrings/plesk.gpg

Types: deb
URIs: Index of /PHP83_17
Suites: resolute
Components: all
Signed-By: /etc/apt/keyrings/plesk.gpg

Types: deb
URIs: Index of /PHP84_17
Suites: resolute
Components: all
Signed-By: /etc/apt/keyrings/plesk.gpg

Types: deb
URIs: Index of /PHP85_17
Suites: resolute
Components: all
Signed-By: /etc/apt/keyrings/plesk.gpg

Types: deb
URIs: Index of /pool/WPB_18.0.69_88
Suites: all
Components: all
Signed-By: /etc/apt/keyrings/plesk.gpg
root@friendly-gauss:/home/administrator# ls -l /etc/apt/keyrings/
total 12
-rw-r--r-- 1 root root 1735 Oct 26 18:36 plesk-ext-watchdog.gpg
-rw-r--r-- 1 root root 8089 Oct 28 16:05 plesk.gpg

Thanks for your help and support!

Martin

 

[tessa67]

Hi @swemp,

Same root cause as in cartapps’ thread, so a quick summary:

1. Duplicate repo entries (the long list of “configured multiple times” warnings)
Your Plesk repos are defined twice: once in the old one-line plesk.list (lines 3-5) and once in the newer deb822 plesk.sources (lines 4-6). Ubuntu 26.04 uses the .sources format, so one of the two is a leftover. That’s just noise, not a real error.

2. The actual error (NO_PUBKEY E9299045CE550E57)
Only one repo fails in your output: WATCHDOG_3.1.0. That’s an older Watchdog repo that apt can’t verify with the keys it has. Your log doesn’t show which file that entry lives in or which key it points to, so I can’t say yet whether it’s a stale entry or just a missing signed-by. Please don’t delete anything yet.
The “Missing Signed-By” notices for Imunify360/TuxCare are only notices, you can ignore them.
Could you post the output of these?

ls -l /etc/apt/sources.list.d/
cat /etc/apt/sources.list.d/plesk.list
cat /etc/apt/sources.list.d/plesk.sources
ls -l /etc/apt/keyrings/

Also, does apt update show a second failing Plesk repo besides WATCHDOG_3.1.0 (e.g. an older pool/PSA_... entry)? Your pasted log doesn’t show one, but it may just be cut off. With the file contents we can tell you exactly which lines to remove.

 

[tessa67]

Hi @swemp,

Thanks, that helps a lot. Two things so far:

1. The duplicates
plesk.list and plesk.sources both contain PHP83, PHP84 and PHP85. Note that for .sources files apt reports stanza numbers, not line numbers, which is why you saw “plesk.sources:4, :5, :6”. The timestamps (all your .list.bak and .sources files from Oct 8) look like the system was converted with apt modernize-sources. Plesk then wrote fresh .list files again on Oct 26 and today. That’s my guess from the dates, not proven.

2. The WATCHDOG_3.1.0 error
The most suspicious part is plesk-ext-watchdog: you have a .list (Oct 26), a .sources (Oct 8) and a separate plesk-ext-watchdog.gpg key (Oct 26). My guess is the old .sources still points to 3.1.0 with a different key, but I can’t confirm that without seeing the files.

Could you post these (please in a code block, your plesk.list output got cut off)?

cat /etc/apt/sources.list.d/plesk-ext-watchdog.list
cat /etc/apt/sources.list.d/plesk-ext-watchdog.sources
cat /etc/apt/sources.list.d/plesk.list
gpg --show-keys /etc/apt/keyrings/plesk-ext-watchdog.gpg
gpg --show-keys /etc/apt/keyrings/plesk.gpg

Also, did you run the >> GPG command from above today? plesk.gpg was modified at 16:05 and it’s fairly big, so please don’t run it again. Don’t delete anything yet, once we see those files the fix should be a one-liner.

Regards
Tessa

 

[swemp]

cat /etc/apt/sources.list.d/plesk-ext-w atchdog.list
deb [arch=amd64 signed-by=/etc/apt/keyrings/plesk-ext-watchdog.gpg] http://autoi nstall.plesk.com/WATCHDOG_3.3.0 resolute all
cat /etc/apt/sources.list.d/plesk-ext-watchdog.sources
Types: deb
URIs: Index of /WATCHDOG_3.1.0
Suites: resolute
Components: all
Signed-By: /etc/apt/keyrings/plesk-ext-watchdog.gpg
cat /etc/apt/sources.list.d/plesk.list
## Persistent repositories for Plesk Products.
deb [signed-by=/etc/apt/keyrings/plesk.gpg] Index of /pool/PSA_18.0.81_20292 resolute extras
deb [signed-by=/etc/apt/keyrings/plesk.gpg] Index of /PHP83_17 resolute all
deb [signed-by=/etc/apt/keyrings/plesk.gpg] Index of /PHP84_17 resolute all
deb [signed-by=/etc/apt/keyrings/plesk.gpg] Index of /PHP85_17 resolute all
gpg --show-keys /etc/apt/keyrings/plesk-ext-watchdog.gpg
gpg: directory '/root/.gnupg' created
gpg: keybox '/root/.gnupg/pubring.kbx' created
gpg: /root/.gnupg/trustdb.gpg: trustdb created
pub rsa3072 2026-08-18 [SC]
43C5DA0DBF8B7DE1457C94285B6AB2160B50DB96
uid Plesk Team <[email protected]>
sub rsa3072 2026-08-18 [E]
gpg --show-keys /etc/apt/keyrings/plesk-ext-watchdog.gpg
gpg: directory '/root/.gnupg' created
gpg: keybox '/root/.gnupg/pubring.kbx' created
gpg: /root/.gnupg/trustdb.gpg: trustdb created
pub rsa3072 2026-08-18 [SC]
43C5DA0DBF8B7DE1457C94285B6AB2160B50DB96
uid Plesk Team <[email protected]>
sub rsa3072 2026-08-18 [E]

root@friendly-gauss:/home/administrator# gpg --show-keys /etc/apt/keyrings/plesk.gpg
pub rsa3072 2026-08-18 [SC]
43C5DA0DBF8B7DE1457C94285B6AB2160B50DB96
uid Plesk Team <[email protected]>
sub rsa3072 2026-08-18 [E]

pub rsa3072 2025-03-05 [SC]
6C191325088ED83A618EC0C2E9299045CE550E57
uid Plesk Team <[email protected]>
sub rsa3072 2025-03-05 [E]

pub dsa1024 2015-08-04 [SC]
8BADC1A02FC9C07FB8C20EC0BD11A6AA914BDF7E
uid Plesk Team <[email protected]>
sub elg2048 2015-08-04 [E]

pub rsa3072 2025-03-05 [SC]
6C191325088ED83A618EC0C2E9299045CE550E57
uid Plesk Team <[email protected]>
sub rsa3072 2025-03-05 [E]

pub rsa3072 2026-08-18 [SC]
43C5DA0DBF8B7DE1457C94285B6AB2160B50DB96
uid Plesk Team <[email protected]>
sub rsa3072 2026-08-18 [E]

 

[tessa67]

Hi @swemp,

Found it.

Your plesk-ext-watchdog.sources still points to the old WATCHDOG_3.1.0 repo, but its keyring plesk-ext-watchdog.gpg only contains the new 2026 key "...DB96" The missing key from the error "E9299045CE550E57" is the old 2025 Plesk key. It’s in plesk.gpg, but not in the watchdog keyring, so apt can’t verify 3.1.0. That’s also why re-importing into plesk.gpg changed nothing.

Your plesk-ext-watchdog.list already has the current WATCHDOG_3.3.0 repo and that one works fine, so the old .sources file is just a stale leftover (probably from the Oct 8 apt modernize-sources run). Move it out of the way instead of deleting it:

mv /etc/apt/sources.list.d/plesk-ext-watchdog.sources /root/plesk-ext-watchdog.sources.bak
apt update

The NO_PUBKEY error should be gone after that. The “configured multiple times” warnings for PHP83/84/85 are only cosmetic (same repos in plesk.list and plesk.sources). Since Plesk rewrote plesk.list today, they may come back after updates.

Regards
Tessa

 

[mizar]

Hello,

At this moment, Plesk don't use deb822 *.sources files, only old *.list files. It seems you are call `apt modernize` or similar. So just remove automatically converted `/etc/apt/plesk*.sources`, because it likely contains links to the old repos.

 

[learning_curve]

~~ At this moment, Plesk don't use deb822 *.sources files, only old *.list files ~~

Is there an ETA for when Plesk will?
As posted early, Ubuntu began to implement their change over two years ago now, with the release of 24.04 LTS.
On ours and other servers that are running 26.04 LTS, Plesk is the only remaining old *.list file that's still active & being used.

 

[cartapps]

Hi @swemp,

Found it.

Your plesk-ext-watchdog.sources still points to the old WATCHDOG_3.1.0 repo, but its keyring plesk-ext-watchdog.gpg only contains the new 2026 key "...DB96" The missing key from the error "E9299045CE550E57" is the old 2025 Plesk key. It’s in plesk.gpg, but not in the watchdog keyring, so apt can’t verify 3.1.0. That’s also why re-importing into plesk.gpg changed nothing.

Your plesk-ext-watchdog.list already has the current WATCHDOG_3.3.0 repo and that one works fine, so the old .sources file is just a stale leftover (probably from the Oct 8 apt modernize-sources run). Move it out of the way instead of deleting it:

mv /etc/apt/sources.list.d/plesk-ext-watchdog.sources /root/plesk-ext-watchdog.sources.bak
apt update

The NO_PUBKEY error should be gone after that. The “configured multiple times” warnings for PHP83/84/85 are only cosmetic (same repos in plesk.list and plesk.sources). Since Plesk rewrote plesk.list today, they may come back after updates.

Regards
Tessa

Okay i have similar results as swemp.
i understood about WATCHDOG_3.1.0.
when i run a apt update command it only shows the WATCHDOG_3.1.0 Error.

But when i run plesk installer --select-release-latest --upgrade-installed-components to update plesk via ssh, it shows one more error.

Err:16 Index of /pool/PSA_18.0.81_19954 resolute InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY E9299045CE550E57

Everything else is just same in the attachment above. Ignored Missing Signed-By, configured multiple times warnings.

 

[tessa67]

Hi @cartapps,

Thanks, that narrows it down. The Watchdog error is the one from swemp’s thread (stale plesk-ext-watchdog.sources pointing to 3.1.0), so please do that fix first:

mv /etc/apt/sources.list.d/plesk-ext-watchdog.sources /root/plesk-ext-watchdog.sources.bak
apt update

The second error (PSA_18.0.81_19954) is a different entry, and your first post already had it. It’s odd that plain apt update doesn’t show it now, but the installer does. My guess is the installer uses its own temporary repo entry or a file that apt doesn’t read the same way, but I can’t confirm that from the logs. To find out where it lives, please post:

grep -rn “PSA_18.0.81_19954” /etc/apt/
ls -l /etc/apt/sources.list.d/ /etc/apt/keyrings/
gpg --show-keys /etc/apt/keyrings/plesk.gpg

The last command shows which keys plesk.gpg has. We’re looking for 6C19...0E57, the old 2025 key. If it’s missing there, that’s why the PSA entry fails. Please don’t delete anything yet, and then run the installer again after the Watchdog fix and tell us whether the PSA error is still there.

Regards
Tessa

 

[tessa67]

Hi @cartapps, @swemp,

Mizar’s tip fits what we’re seeing. The .sources files with the Oct 8 timestamps look like the result of an automatic apt modernize-sources run, and they still point to old repos (WATCHDOG_3.1.0, and most likely the old PSA_18.0.81_19954 as well). Plesk itself seems to only write .list files for now, so the .sources copies are leftovers. Small correction: the files live in /etc/apt/sources.list.d/.

So instead of the single watchdog file from before, you can move both Plesk-related ones out of the way (moving, not deleting, so you can always put them back):

mkdir -p /root/apt-sources-bak
mv /etc/apt/sources.list.d/plesk*.sources /root/apt-sources-bak/
apt update

One thing to watch: swemp’s plesk.sources contained a few repos that were missing in plesk.list (PHP81, PHP82, WPB). I don’t know whether Plesk re-adds those on its own. If you use PHP 8.1/8.2 from Plesk, check after the move that it still shows up and updates fine, and if not, move the file back.

Leave 50sw_autoinstaller.sources and the Imunify/TuxCare ones alone unless they throw actual errors. The “Missing Signed-By” notices are harmless.

Afterwards please run apt update and the Plesk installer once more and tell us if the NO_PUBKEY errors are gone. If cartapps still sees the PSA_18.0.81_19954 error, the grep output from my last post will show where it comes from.

Regards
Tessa

 

[tessa67]

Is there an ETA for when Plesk will?
As posted early, Ubuntu began to implement their change over two years ago now, with the release of 24.04 LTS.
On ours and other servers that are running 26.04 LTS, Plesk is the only remaining old *.list file that's still active & being used.

Hi @learning_curve, no ETA that I know of. Might be worth a vote/request on features.plesk.com, since it would avoid exactly this kind of .list vs .sources mix-up after apt modernize-sources.