ubuntu – Why does systemd-resolve stop my java server?

I came across this problem where every few days one of my Java servers is dying. To find out why, I ran cat /var/log/syslog which produces:

Sep 21 06:36:24 ip-172-31-42-5 systemd-timesyncd(16235): Network configuration changed, trying to establish connection.
Sep 21 06:36:24 ip-172-31-42-5 systemd-timesyncd(16235): Synchronized to time server 91.189.91.157:123 (ntp.ubuntu.com).
Sep 21 06:46:45 ip-172-31-42-5 systemd(1): Starting Daily apt upgrade and clean activities...
Sep 21 06:47:35 ip-172-31-42-5 kernel: (5731409.370359) systemd-resolve invoked oom-killer: gfp_mask=0x14200ca(GFP_HIGHUSER_MOVABLE), nodemask=(null), order=0, oom_score_adj=0
...(skipping a bunch) ...
Sep 21 06:47:35 ip-172-31-42-5 kernel: (5731409.370580) Out of memory: Kill process 28251 (java) score 368 or sacrifice child
Sep 21 06:47:35 ip-172-31-42-5 kernel: (5731409.374244) Killed process 28251 (java) total-vm:2613628kB, anon-rss:178048kB, file-rss:0kB, shmem-rss:0kB
Sep 21 06:47:35 ip-172-31-42-5 kernel: (5731409.403233) oom_reaper: reaped process 28251 (java), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB

After reading this post, I learned that the oom_reaper stops the largest memory-intensive process when any process tries to allocate too much memory. Well, I suspect that systemd-resolve trying to request a ridiculous amount of memory, and then the reaper stops my bad java process.

I could handle that by putting it down vm.oom_kill_allocating_task As suggested in the link above, I'm trying to figure out why systemd-resolve is trying to request such an absurd amount of memory. Does anyone know what the basic problem is here?

Edit: When the Java server is running, memory usage is only 234M / 460M

SQL Server 2017 uses no free space

On one of our read servers (SQL Server 2017 CU2 – yes, outdated), page life has recently dropped from an average of 15,000 seconds to 250 seconds.

It is one of 2 Load Balanced Read servers and its twin has not experienced this decline.

I find it interesting to note that the Free Memory (KB) performance counter is 303,100,000, while its twin uses far more free memory: The performance indicator is 30,125,800 (an order of magnitude smaller).

Both servers have a target server storage of 409,000,000.

I'm assuming that the PLE crashed heavily because SQL Server does not take up the free space, so it's not cached as before. How do I find out what's going on?

ssh – remote access to the server

I'm new to the network environment and I'm trying to sign in to a Linux system with an SSH client on a Mac, but I'm having problems. I found the terminal and clicked on it, and a Bash 80 by 24 window with the following content appears

Last login: Sat 21.09. 15:33:10 on xxxx
Aarons MacBook Air: ~ aaronxxxxx $

I use x to hide personal information. After playing around I found the new remote connection, but after this step I am super lost and would like to have a tutorial. I have the server name and my login and password, but I have entered all this and have no success. Any help will be super awesome.

Detect remote requests from the same user page view on the local server side

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ntpd – Setting up an NTP server from a LAN KoD package has inconsistent xmt / org / rec timestamps. To ignore

I set up an NTP server on my Ubuntu computer and want the Raspberry Pi computers and (possibly) Windows computers to be synced from this server. I thought things would be pretty simple, but on my one client computer I get an error:

ntpd(3662): receive: KoD packet from 192.168.0.199 has inconsistent xmt/org/rec timestamps.  Ignoring.

I could not find anything useful in this message and am looking for help here.

This is my ntp.conf on my server – it's pretty simple:

# /etc/ntp.conf, configuration for ntpd; see ntp.conf(5) for help

driftfile /var/lib/ntp/ntp.drift

# Leap seconds definition provided by tzdata
leapfile /usr/share/zoneinfo/leap-seconds.list

# Enable this if you want statistics to be logged.
statsdir /var/log/ntpstats/

statistics loopstats peerstats clockstats
filegen loopstats file loopstats type day enable
filegen peerstats file peerstats type day enable
filegen clockstats file clockstats type day enable

# Specify one or more NTP servers.
#server 192.168.0.199
server 0.ca.pool.ntp.org
server 1.ca.pool.ntp.org
server 2.ca.pool.ntp.org
server 3.ca.pool.ntp.org

# Use servers from the NTP Pool Project. Approved by Ubuntu Technical Board
# on 2011-02-08 (LP: #104525). See http://www.pool.ntp.org/join.html for
# more information.
pool 0.ca.pool.ntp.org iburst
pool 1.ca.pool.ntp.org iburst
pool 2.ca.pool.ntp.org iburst
pool 3.ca.pool.ntp.org iburst
pool 0.ubuntu.pool.ntp.org iburst
pool 1.ubuntu.pool.ntp.org iburst
pool 2.ubuntu.pool.ntp.org iburst
pool 3.ubuntu.pool.ntp.org iburst
# Use Ubuntu's ntp server as a fallback.
pool ntp.ubuntu.com

# Access control configuration; see /usr/share/doc/ntp-doc/html/accopt.html for
# details.  The web page 
# might also be helpful.
#
# Note that "restrict" applies to both servers and clients, so a configuration
# that might be intended to block requests from certain clients could also end
# up blocking replies from your own upstream servers.

# By default, exchange time with everybody, but don't allow configuration.
restrict -4 default kod notrap nomodify nopeer noquery limited
#restrict -6 default kod notrap nomodify nopeer noquery limited

# Local users may interrogate the ntp server more closely.
restrict 127.0.0.1
#restrict ::1

# Needed for adding pool entries
#restrict source notrap nomodify noquery

# Clients from this (example!) subnet have unlimited access, but only if
# cryptographically authenticated.
#restrict 192.168.123.0 mask 255.255.255.0 notrust


# If you want to provide time to your local subnet, change the next line.
# (Again, the address is an example only.)
broadcast 192.168.111.255

# If you want to listen to time broadcasts on your local subnet, de-comment the
# next lines.  Please do this only if you trust everybody on the network!
#disable auth
#broadcastclient

#Changes recquired to use pps synchonisation as explained in documentation:
#http://www.ntp.org/ntpfaq/NTP-s-config-adv.htm#AEN3918

#server 127.127.8.1 mode 135 prefer    # Meinberg GPS167 with PPS
#fudge 127.127.8.1 time1 0.0042        # relative to PPS for my hardware

#server 127.127.22.1                   # ATOM(PPS)
#fudge 127.127.22.1 flag3 1            # enable PPS API

My ntp.conf on my client (Raspberry Pi) – again quite simple:

# /etc/ntp.conf, configuration for ntpd; see ntp.conf(5) for help

driftfile /var/lib/ntp/ntp.drift

# Enable this if you want statistics to be logged.
statsdir /var/log/ntpstats/

statistics loopstats peerstats clockstats
filegen loopstats file loopstats type day enable
filegen peerstats file peerstats type day enable
filegen clockstats file clockstats type day enable


# You do need to talk to an NTP server or two (or three).
server 192.168.0.199

# pool.ntp.org maps to about 1000 low-stratum NTP servers.  Your server will
# pick a different set every time it starts up.  Please consider joining the
# pool: 
#pool 0.debian.pool.ntp.org iburst
#pool 1.debian.pool.ntp.org iburst
#pool 2.debian.pool.ntp.org iburst
#pool 3.debian.pool.ntp.org iburst

# By default, exchange time with everybody, but don't allow configuration.
restrict -4 default kod notrap nomodify nopeer noquery limited
restrict -6 default kod notrap nomodify nopeer noquery limited

# Local users may interrogate the ntp server more closely.
restrict 127.0.0.1
restrict ::1

# Needed for adding pool entries
restrict source notrap nomodify noquery

Javascript – How do I use NetlifyCMS on a non-local server?

I use Netlify with GitHub to host a simple blog that's available here and perfectly hosted. The blog works fine here (it's not done yet, but it works). But if I enter / admin in the address bar and press to log in to Github, the following message will be displayed: (no logon screen will be displayed directly to this message)

No authentication provider found
Make sure that you have configured the Github credentials API in the Access pane of your Netlify site dashboard.

Permissions – blocked by the dedicated server due to chmod

So I accidentally ran chmod -x / instead of what I wanted, and that's why a lot of things got broken on my server. Because of this, I can not log in as usual and have to use other methods.

I tried to fix the permissions of the server for accidental chmod, but only got tons of permissions issues that look a bit like "Change the permission of & # 39; / proc / sys / net / etc …" and then it still does not work. I get that too for many other directories.

If you let me know how you can fix this or other information you need, that would be great.

python – Network Programming – asynchronous single-threaded chat server with nicknames only

I'm starting to learn network programming. I've implemented a very simple TCP-based chat server, where users just have to provide the username.
The assumption is that the server does not use additional threads and does not block the sockets. The code:


import sys
import time
import socket
import select


class User:
    def __init__(self, name, sock):
        self.name = name
        self.sock = sock


class Server:
    def __init__(self, host, port):
        self.users = ()

        self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.sock.bind((host, port))

    def accept_usr(self):
        usock, _ = self.sock.accept()
        usock.send(b"Please, choose your username: ")
        uname = usock.recv(1024)
        self.users.append(User(uname, usock))
        _, writes, _ = select.select((), self._usocks(), ())
        for w in writes:
            w.send(bytes(f"{uname} has joined us!", encoding="ascii"))

    def handlerr(self, errs):
        for s in errs:
            s.close()

    def update(self):
        reads, writes, errs = select.select((*self._usocks(), self.sock), self._usocks(), self._usocks())
        for r in reads:
            if r is self.sock:
                self.accept_usr()
            else:
                uname = (u for u in self.users if u.sock is u.sock)(0).name
                msg = r.recv(1024)
                for w in writes:
                    w.send(bytes(f"{uname}: {msg}", encoding="ascii"))
        self.handlerr(errs)

    def run(self):
        self.sock.listen(5)
        while 1:
            self.update()
            time.sleep(0.1)

    def _usocks(self):
        return (u.sock for u in self.users)

if __name__ == "__main__":
    s = Server("localhost", int(sys.argv(1)))
    s.run()

For hints and comments, I would be grateful.

TO EDIT:
One obvious improvement I can think of is storing the mapping of socket-> users in a dictation so that I can quickly determine the author of the sent message.

Nameserver – cPanel PTR with external DNS server

Can someone help me in the following situation:

For example, our VPS hosted in Linode with WHM / cPanel is "hostname" server.meinedomain.com,

Under WHM Home> Service Configuration> Nameserver Selection> I selected the DISABLED option because our DNS server in dnsmadeeasy.com uses it externally

In the Linode Control Panel, I set the reverse DNS to server.mydomain.com. Then I check it with the following tools: https://www.debouncer.com/reverse-dns-check

And the result is confirmed rDNS Forward.

Also use:

dig -x SERVER IP ADDRESS

and the result is so good:

;; ANSWER SECTION:
235.31.19.15.in-addr.arpa. 21599 IN     PTR     server.mydomain.com.

Now my question is:

How do I set the PTR for all domains in server.mydomain.com? Should I set them from dnsmadeeasy.com or what?

Any help appreciated :]