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applications.md

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title: Linux Server Applications breadcrumbs:

  • title: Configuration
  • title: Linux Server --- {% include header.md %}

TODO Migrate the rest of the config notes from the old Google Doc.

Using

{:.no_toc}

  • Debian 10 Buster

Ceph

See Storage: Ceph.

Docker & Docker Compose

TODO

Setup

  1. Install Docker (Debian).
  2. Install Docker Compose.
  3. Install Docker Compose command completion.
  4. (Optional) Setup swap limit:
    • If docker info contains WARNING: No swap limit support, it's not working and should maybe be fixed.
    • It incurs a small performance degredation and is optional but recommended.
    • In /etc/default/grub, add cgroup_enable=memory swapaccount=1 to GRUB_CMDLINE_LINUX.
    • Run update-grub and reboot.

Docker Compose No-Exec Tmp-Dir Fix

Docker Compose will fail to work if /tmp has noexec.

  1. Move /usr/local/bin/docker-compose to /usr/local/bin/docker-compose-normal.
  2. Create /usr/local/bin/docker-compose with the contents below and make it executable.

  3. Create the new TMPDIR dir.

    #!/bin/bash
# Some dir without noexec
export TMPDIR=/var/lib/docker-compose-tmp
/usr/local/bin/docker-compose-normal "$@"

Fail2ban

Setup

  1. Install fail2ban.
  2. Fix the firewall first so it configures itself correctly wrt. firewall blocking.
  3. Check the status with fail2ban-client status [sshd].

Intel SSD Data Center Tool (isdct)

Setup

  1. Download the ZIP for Linux from Intel's site.
  2. Install the AMD64 deb package.

Usage

  • Command syntax: isdct <verb> [options] [targets] [properties]
    • Target may be either index (as seen in show) or serial number.
  • Show all SSDs: isdct show -intelssd
  • Show SSD properties: isdct show -all -intelssd [target]
  • Show health: isdct show -sensor
  • Upgrade firmware: isdct load -intelssd <target>
  • Set physical sector size: isdct set -intelssd <target> PhysicalSectorSize=<512|4096>
    • 4k is generally the most optimal choice.
  • Prepare a drive for removal by putting it in standby: isdct start -intelssd <target> -standby
  • Show speed: isdct show -a -intelssd [target] | grep -i speed
  • Fix SATA 3.0 speed: isdct set -intelssd <target> PhySpeed=6
    • Check before and after either with isdct or smartctl.

Change the Capacity

  1. Remove all partitions from the drive.
  2. Remove all data: isdct delete -intelssd <target>
  3. (Optional) Set the physical sector size: isdct set -intelssd <target> PhysicalSectorSize=<512|4096>
  4. Set the new size: isdct set -intelssd <target> MaximumLBA=<size>
    • If this fails, run isdct set -system EnableLSIAdapter=true. It will add another "version" of the SSDs, which you can try again with.
    • The size can be specified either as "native", the LBA count, percent (x%) or in gigabytes (xGB). Use "native" unless you have a reason not to.
  5. Prepare it for removal: isdct start -intelssd <target> -standby
  6. Reconnect the drives or restart the system.

ISC DHCP Server

Notes

  • DHCPv4 uses raw sockets, so it bypasses the firewall (i.e. no firewall rules are needed). DHCPv6, however, does not. This includes the respective clients as well.
  • The DHCPv6 server is typically used with radvd for router advertisements.

Setup

  1. Install and enable isc-dhcp-server.
  2. Setup config files:
    • DHCPv4: /etc/dhcp/dhcpd.conf
    • DHCPv6 (optional): /etc/dhcp/dhcpd6.conf
  3. If using systemd-networkd, fix wrong startup order:
    • TODO

Configuration

  • Always specify the authorative statement in subnet declarations so that the server will reply with DHCPNAK for misconfigured clients. This may significantly reduce reconfiguration delay when a client moves between subnets.
  • For range6, prefer using CIDR notation. If using range notation, try to align the start and end on a CIDR block to avoid excessive memory usage.
  • DHCPv6 uses lease pools of 9973 entries, so using range sizes below this number may be preferable as a very general reference. /116 gives 8191 addresses.

ntopng

Setup

  1. Install ntopng.
  2. Make sure service ntopng is enabled and running.
  3. Fix log dir owner: chown nobody:nogroup /var/log/ntopng
  4. Configure:
    1. Open /etc/ntopng.conf.
    2. Add -W=<new_port> to enable HTTPS.
    3. (Optional) Set -w=0 to disable HTTP.
  5. Restart it (takes a while).

ntpd

Setup

  1. Disable systemd-timesyncd NTP client by disabling and stopping systemd-timesyncd.
  2. Install ntp.
  3. In /etc/ntp.conf, replace existing servers/pools with ntp.justervesenet.no with the iburst option.
  4. Test with ntpq -pn (it may take a minute to synchronize).

Postfix

Satellite system

Notes

  • When using an SMTP relay, the original IP address will likely be found in the mail headers.
  • Make sure DNS is configured correctly (SPF, DKIM, DMARC).

Setup

  1. Install: postfix libsasl2-modules mailutils
    • If asked, choose to configure Postfix as a satellite system.
  2. Set the FQDN:
    1. Update it in /etc/postfix/main.cf.
    2. Link mailname to hostname (must be FQDN): ln -sf /etc/hostname /etc/mailname
  3. Update the root alias in /etc/aliases and run newaliases.
  4. Update the main.cf config (example not provided here).
    1. Only listen to localhost: Set “inet_interfaces = loopback-only”
    2. Disable relaying: Set “mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128”
    3. Anonymize banner: “smtpd_banner = $myhostname ESMTP”
  5. Relay guides:
    1. Mailgun:
      1. How To Start Sending Email (Mailgun)
      2. How to Set Up a Mail Relay with Postfix and Mailgun on Ubuntu 16.04 (DigitalOcean)
    2. SendGrid:
      1. Postfix (SendGrid)
      2. Use API-key with permission to send mail only.
      3. The API-key username is apikey.
  6. Setup address rewrite rules:
    • For fixing the To and From fields, which is typically from root to root.
    • Add the rewrite config (see example below).
    • Reference the config using smtp_header_checks in the main config.
    • Test: postmap -fq "From: root@<FQDN>" regexp:smtp_header_checks
  7. Setup relay credentials (SASL):
    1. Credentials file: /etc/postfix/sasl_passwd
    2. Add your credentials using format: [relay_domain]:port user@domain:password
    3. Run: postmap sasl_passwd
    4. Fix permissions: chmod 600 sasl_passwd*
  8. Restart postfix.
  9. Try sending an email: echo "Test from $(hostname) at time $(date)." | mail -s "Test" root

Examples

# File: smtp_header_checks

/^From:\s*.*\S+@node\.example\.bet.*.*$/ REPLACE From: "Node" <node@example.net>
/^To:\s*.*\S+@node\.example\.net.*$/ REPLACE To: "Someone" <someone@example.net>

Usage

  • Send a test mail: echo "Test from $HOSTNAME at time $(date)." | mail -s "Test" root
  • Test the config: postconf > /dev/null
  • Print the config: postconf -n
  • If mails are stuck in the mail queue (mailq) because of previous errors, run postqueue -f to flush them.

Pterodactyl

Setup

  • Note: The node must be publicly accessable.
  • Follow the official guide.

Game Servers

CSGO

  • It uses a ton of storage, between 20 and 30 GB last I checked. If you useless, the installer will fail with some useless error message.
  • Use app ID 730 in Steam Game Server Account Manager, regardless of which app ID the server was created with. If you use e.g. 740, the server will not be able to log into Steam.

Router Advertisement Daemon (radvd)

Setup

  1. Install and enable radvd.
  2. Setup config file: /etc/radvd.conf

TFTP-HPA

Setup

  1. Install tftpd-hpa.
  2. Update /etc/default/tftpd-hpa based on the config below.
  3. Create the folder /var/tftp with permissions 777 and user-group pair tftp:tftp.
  4. Restart it.
  5. If it shouldn't automatically start, disble it.

Files

# File: /etc/default/tftpd-hpa

TFTP_USERNAME="tftp"
TFTP_DIRECTORY="/var/tftp"
TFTP_ADDRESS=":69"
TFTP_OPTIONS="--create --secure"

Unbound

Setup

  1. Install: unbound dns-root-data
  2. Setup the config: /etc/unbound/unbound.conf
  3. Add hostname variants to /etc/hosts.
  4. Configure it in /etc/resolv.conf:
    1. nameserver 127.0.0.1
    2. search <domain>
    3. domain <domain>
  5. Configure it in /etc/systemd/resolved.conf:
    1. DNSStubListener=no
    2. DNS=127.0.0.1
    3. Restart systemd-resolved.
  6. Test DNSSEC:
    1. drill sigfail.verteiltesysteme.net should give an rcode of SERVFAIL.
    2. drill sigok.verteiltesysteme.net should give an rcode of NOERROR.
  7. Make sure dns-root-data is updating root hints in file /usr/share/dns/root.hints.

Troubleshooting

  • It sometimes stops resolving names and responds with "servfail".
    • I don't know why. Restarting it works.

Notes

  • Use DNS over HTTPS/TLS.
  • Setup private addresses for DNS rebinding prevention.

UniFi

Setup

Using the unofficial Docker image by jacobalberty.

  1. Add a system user named "unifi": useradd -r unifi
  2. Allow the ports through the firewall: See UniFi - Ports Used.
  3. Add a Docker Compose file. See docker-compose.yml.
    • Use host networking mode for L2 adoption to work (if you're not using L3 or SSH adoption).
  4. Start the container, open the webpage and follow the wizard.

ZFS

See Storage: ZFS.

{% include footer.md %}