glusterfs with localhost ( nodes on different servers – glusterfs volume with 3 replicas

Binding the GlusterFS nodes on a physical interface may lead to local availability problems even for replication nodes. Bringing down the physical interface will bring down the nodes, even the local replica for the local mounts and applications.

  • 100% local uptime. The local replica will be 100% available. The loopback interface is always in the upstate! Network interfaces are not 100% upstate, because of network reload or cable unplug. Cable unplug (or port down for a switch configuration reload) could lead to a short time unavailable of the local node even for the local system!
  • node resolve rely on /etc/hosts records, not network and remote DNS system.
  • No speed limit. The read from the local system through the loopback interface could easily increase above 1G or even 10G. Probably, building nodes with replicas over a 1G network is much more affected than a network with 10G connectivity. Reading from a node relying on a loopback interface could pass 10G, even though the server is connected to a 1G network!

An addition note – another kind of the proposed solution here is to use a virtual interface to bind the IP of the GlusterFS brick. The most common type of virtual interface is using a bridge interface for the IP.

The example here is to bring a GlusterFS volume in replication mode with 3 servers, i.e. 3 replicas. Each server may mount locally the GlusterFS volume with name VOL1 and it would not get unavailable if the main interface

  • server’s hostname: node1, hostname for the replica brick glnode1. IP:, but the node1 locally is resolved as through /etc/hosts.
  • server’s hostname: node2, hostname for the replica brick glnode2. IP:, but the node1 locally is resolved as through /etc/hosts.
  • server’s hostname: node3, hostname for the replica brick glnode3 IP:, but the node3 locally is resolved as through /etc/hosts.

Of course, the server’s hostname could be used, but it better to have a separate domain for the GlusterFS bricks. Sometimes server hostnames should be a real IP or some software may rely on it, too.

And here are all the commands to bring up the GlusterFS volume on 3 servers:

STEP 1) Install GlusterFS software and initial configuration.

There are GlisterFS packages in the official CentOS 8, but a newer version is supported in the Storage SIG. The GlusterFS version installed in this article is 8.4. Install the software under node1, node2, and node3.

yum install -y centos-release-gluster
yum install -y glusterfs-server

Add the following lines at the end of node1:/etc/hosts file. glnode1 glnode2 glnode3

Add the following lines at the end of node2:/etc/hosts file. glnode1 glnode2 glnode3

Add the following lines at the end of node3:/etc/hosts file. glnode1 glnode2 glnode3

Start the GlusterFS service on the three nodes

systemctl start glusterd

Mount the storage device if any and make the directory where the GlusterFS brick will reside:

mount /mnt/storage/
mkdir -p /mnt/storage/gluster/brick

STEP 2) Configure the firewall.

CentOS 8 uses firewalld and here a new zone for the GlusterFS is created and the GlusterFS service is added in the whitelist of the new zone. The three IPs of the nodes are also added in the new zone:

firewall-cmd --permanent --new-zone=glusternodes
firewall-cmd --permanent --zone=glusternodes --add-source=
firewall-cmd --permanent --zone=glusternodes --add-source=
firewall-cmd --permanent --zone=glusternodes --add-source=
firewall-cmd --permanent --zone=glusternodes --add-service=glusterfs
firewall-cmd --reload

STEP 3) Add peers to the GlusterFS cluster and create a 3 node replica volume.

gluster peer probe glnode2
gluster peer probe glnode3
gluster volume create VOL1 replica 3 transport tcp glnode1:/mnt/storage/gluster/brick glnode2:/mnt/storage/gluster/brick glnode3:/mnt/storage/gluster/brick
gluster volume start VOL1

The GlusterFS volume can be mounted with:

mount -t glusterfs glnode1:/VOL1 /mnt/VOL1/

And /etc/fstab sample line:

glnode1:/VOL1 /mnt/VOL1 glusterfs defaults,noatime,direct-io-mode=disable 0 0

Always use the local hostname for the current node server. If you would like to mount the volume VOL1 on node1, use glnode1:/VOL1 and so on.
Bringing down the physical interface of the server, which is connected to the Internet (aka the network interface with the real IP) would not make the GlusterFS brick unavailable for the local mounts and applications.

In a cluster with only replicas, the local application will just continue using the mounted GlusterFS volume (or native GlusterFS clients) relying only on the local Gluster brick till the main Internet connection comes back.

Create 3 node replica volume – the whole output

[root@node1 ~]# yum install -y centos-release-gluster
CentOS Stream 8 - AppStream                                                                                 5.8 MB/s | 6.7 MB     00:01    
CentOS Stream 8 - BaseOS                                                                                    2.0 MB/s | 2.3 MB     00:01    
CentOS Stream 8 - Extras                                                                                     22 kB/s | 9.1 kB     00:00    
Dependencies resolved.
 Package                                          Architecture              Version                         Repository                 Size
 centos-release-gluster8                          noarch                    1.0-1.el8                       extras                    9.3 k
Installing dependencies:
 centos-release-storage-common                    noarch                    2-2.el8                         extras                    9.4 k

Transaction Summary
Install  2 Packages

Total download size: 19 k
Installed size: 2.4 k
Downloading Packages:
(1/2): centos-release-gluster8-1.0-1.el8.noarch.rpm                                                         136 kB/s | 9.3 kB     00:00    
(2/2): centos-release-storage-common-2-2.el8.noarch.rpm                                                     145 kB/s | 9.4 kB     00:00    
Total                                                                                                        27 kB/s |  19 kB     00:00     
warning: /var/cache/dnf/extras-9705a089504ff150/packages/centos-release-gluster8-1.0-1.el8.noarch.rpm: Header V3 RSA/SHA256 Signature, key ID 8483c65d: NOKEY
CentOS Stream 8 - Extras                                                                                    725 kB/s | 1.6 kB     00:00    
Importing GPG key 0x8483C65D:
 Userid     : "CentOS (CentOS Official Signing Key) <>"
 Fingerprint: 99DB 70FA E1D7 CE22 7FB6 4882 05B5 55B3 8483 C65D
 From       : /etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial
Key imported successfully
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
  Preparing        :                                                                                                                    1/1 
  Installing       : centos-release-storage-common-2-2.el8.noarch                                                                       1/2 
  Installing       : centos-release-gluster8-1.0-1.el8.noarch                                                                           2/2 
  Running scriptlet: centos-release-gluster8-1.0-1.el8.noarch                                                                           2/2 
  Verifying        : centos-release-gluster8-1.0-1.el8.noarch                                                                           1/2 
  Verifying        : centos-release-storage-common-2-2.el8.noarch                                                                       2/2 

  centos-release-gluster8-1.0-1.el8.noarch                           centos-release-storage-common-2-2.el8.noarch                          

[root@node1 ~]# yum install -y glusterfs-server
Last metadata expiration check: 0:00:14 ago on Wed Apr 14 13:01:50 2021.
Dependencies resolved.
 Package                                      Architecture          Version                            Repository                      Size
 glusterfs-server                             x86_64                8.4-1.el8                          centos-gluster8                1.4 M
Installing dependencies:
 attr                                         x86_64                2.4.48-3.el8                       baseos                          68 k
 device-mapper-event                          x86_64                8:1.02.175-5.el8                   baseos                         269 k
 device-mapper-event-libs                     x86_64                8:1.02.175-5.el8                   baseos                         269 k
 device-mapper-persistent-data                x86_64                0.8.5-4.el8                        baseos                         468 k
 glusterfs                                    x86_64                8.4-1.el8                          centos-gluster8                689 k
 glusterfs-cli                                x86_64                8.4-1.el8                          centos-gluster8                214 k
 glusterfs-client-xlators                     x86_64                8.4-1.el8                          centos-gluster8                899 k
 glusterfs-fuse                               x86_64                8.4-1.el8                          centos-gluster8                171 k
 libaio                                       x86_64                0.3.112-1.el8                      baseos                          33 k
 libgfapi0                                    x86_64                8.4-1.el8                          centos-gluster8                125 k
 libgfchangelog0                              x86_64                8.4-1.el8                          centos-gluster8                 67 k
 libgfrpc0                                    x86_64                8.4-1.el8                          centos-gluster8                 89 k
 libgfxdr0                                    x86_64                8.4-1.el8                          centos-gluster8                 61 k
 libglusterd0                                 x86_64                8.4-1.el8                          centos-gluster8                 45 k
 libglusterfs0                                x86_64                8.4-1.el8                          centos-gluster8                350 k
 lvm2                                         x86_64                8:2.03.11-5.el8                    baseos                         1.6 M
 lvm2-libs                                    x86_64                8:2.03.11-5.el8                    baseos                         1.1 M
 psmisc                                       x86_64                23.1-5.el8                         baseos                         151 k
 python3-pyxattr                              x86_64                0.5.3-18.el8                       centos-gluster8                 35 k
 rpcbind                                      x86_64                1.2.5-8.el8                        baseos                          70 k
 userspace-rcu                                x86_64                0.10.1-4.el8                       baseos                         101 k

Transaction Summary
Install  22 Packages

Total download size: 8.2 M
Installed size: 24 M
Downloading Packages:
(1/22): glusterfs-cli-8.4-1.el8.x86_64.rpm                                                                  1.1 MB/s | 214 kB     00:00    
(2/22): glusterfs-8.4-1.el8.x86_64.rpm                                                                      2.6 MB/s | 689 kB     00:00    
(3/22): glusterfs-fuse-8.4-1.el8.x86_64.rpm                                                                 1.1 MB/s | 171 kB     00:00    
(4/22): glusterfs-client-xlators-8.4-1.el8.x86_64.rpm                                                       2.3 MB/s | 899 kB     00:00    
(5/22): libgfapi0-8.4-1.el8.x86_64.rpm                                                                      1.8 MB/s | 125 kB     00:00    
(6/22): libgfchangelog0-8.4-1.el8.x86_64.rpm                                                                755 kB/s |  67 kB     00:00    
(7/22): libgfrpc0-8.4-1.el8.x86_64.rpm                                                                      756 kB/s |  89 kB     00:00    
(8/22): libgfxdr0-8.4-1.el8.x86_64.rpm                                                                      579 kB/s |  61 kB     00:00    
(9/22): libglusterd0-8.4-1.el8.x86_64.rpm                                                                   641 kB/s |  45 kB     00:00    
(10/22): glusterfs-server-8.4-1.el8.x86_64.rpm                                                              3.4 MB/s | 1.4 MB     00:00    
(11/22): libglusterfs0-8.4-1.el8.x86_64.rpm                                                                 1.0 MB/s | 350 kB     00:00    
(12/22): python3-pyxattr-0.5.3-18.el8.x86_64.rpm                                                             97 kB/s |  35 kB     00:00    
(13/22): attr-2.4.48-3.el8.x86_64.rpm                                                                        85 kB/s |  68 kB     00:00    
(14/22): device-mapper-event-1.02.175-5.el8.x86_64.rpm                                                      342 kB/s | 269 kB     00:00    
(15/22): device-mapper-event-libs-1.02.175-5.el8.x86_64.rpm                                                 338 kB/s | 269 kB     00:00    
(16/22): libaio-0.3.112-1.el8.x86_64.rpm                                                                    679 kB/s |  33 kB     00:00    
(17/22): device-mapper-persistent-data-0.8.5-4.el8.x86_64.rpm                                               1.5 MB/s | 468 kB     00:00    
(18/22): psmisc-23.1-5.el8.x86_64.rpm                                                                       1.5 MB/s | 151 kB     00:00    
(19/22): rpcbind-1.2.5-8.el8.x86_64.rpm                                                                     1.2 MB/s |  70 kB     00:00    
(20/22): lvm2-libs-2.03.11-5.el8.x86_64.rpm                                                                 3.1 MB/s | 1.1 MB     00:00    
(21/22): userspace-rcu-0.10.1-4.el8.x86_64.rpm                                                              474 kB/s | 101 kB     00:00    
(22/22): lvm2-2.03.11-5.el8.x86_64.rpm                                                                      3.3 MB/s | 1.6 MB     00:00    
Total                                                                                                       2.8 MB/s | 8.2 MB     00:02     
warning: /var/cache/dnf/centos-gluster8-ae72c2c38de8ee20/packages/glusterfs-8.4-1.el8.x86_64.rpm: Header V4 RSA/SHA1 Signature, key ID e451e5b5: NOKEY
CentOS-8 - Gluster 8                                                                                        1.0 MB/s | 1.0 kB     00:00    
Importing GPG key 0xE451E5B5:
 Userid     : "CentOS Storage SIG ( <>"
 Fingerprint: 7412 9C0B 173B 071A 3775 951A D4A2 E50B E451 E5B5
 From       : /etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-SIG-Storage
Key imported successfully
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
  Preparing        :                                                                                                                    1/1 
  Installing       : libgfxdr0-8.4-1.el8.x86_64                                                                                        1/22 
  Running scriptlet: libgfxdr0-8.4-1.el8.x86_64                                                                                        1/22 
  Installing       : libglusterfs0-8.4-1.el8.x86_64                                                                                    2/22 
  Running scriptlet: libglusterfs0-8.4-1.el8.x86_64                                                                                    2/22 
  Installing       : libgfrpc0-8.4-1.el8.x86_64                                                                                        3/22 
  Running scriptlet: libgfrpc0-8.4-1.el8.x86_64                                                                                        3/22 
  Installing       : libaio-0.3.112-1.el8.x86_64                                                                                       4/22 
  Installing       : glusterfs-client-xlators-8.4-1.el8.x86_64                                                                         5/22 
  Installing       : device-mapper-event-libs-8:1.02.175-5.el8.x86_64                                                                  6/22 
  Running scriptlet: glusterfs-8.4-1.el8.x86_64                                                                                        7/22 
  Installing       : glusterfs-8.4-1.el8.x86_64                                                                                        7/22 
  Running scriptlet: glusterfs-8.4-1.el8.x86_64                                                                                        7/22 
  Installing       : libglusterd0-8.4-1.el8.x86_64                                                                                     8/22 
  Running scriptlet: libglusterd0-8.4-1.el8.x86_64                                                                                     8/22 
  Installing       : glusterfs-cli-8.4-1.el8.x86_64                                                                                    9/22 
  Installing       : device-mapper-event-8:1.02.175-5.el8.x86_64                                                                      10/22 
  Running scriptlet: device-mapper-event-8:1.02.175-5.el8.x86_64                                                                      10/22 
  Installing       : lvm2-libs-8:2.03.11-5.el8.x86_64                                                                                 11/22 
  Installing       : libgfapi0-8.4-1.el8.x86_64                                                                                       12/22 
  Running scriptlet: libgfapi0-8.4-1.el8.x86_64                                                                                       12/22 
  Installing       : device-mapper-persistent-data-0.8.5-4.el8.x86_64                                                                 13/22 
  Installing       : lvm2-8:2.03.11-5.el8.x86_64                                                                                      14/22 
  Running scriptlet: lvm2-8:2.03.11-5.el8.x86_64                                                                                      14/22 
  Installing       : libgfchangelog0-8.4-1.el8.x86_64                                                                                 15/22 
  Running scriptlet: libgfchangelog0-8.4-1.el8.x86_64                                                                                 15/22 
  Installing       : userspace-rcu-0.10.1-4.el8.x86_64                                                                                16/22 
  Running scriptlet: userspace-rcu-0.10.1-4.el8.x86_64                                                                                16/22 
  Running scriptlet: rpcbind-1.2.5-8.el8.x86_64                                                                                       17/22 
  Installing       : rpcbind-1.2.5-8.el8.x86_64                                                                                       17/22 
  Running scriptlet: rpcbind-1.2.5-8.el8.x86_64                                                                                       17/22 
  Installing       : psmisc-23.1-5.el8.x86_64                                                                                         18/22 
  Installing       : attr-2.4.48-3.el8.x86_64                                                                                         19/22 
  Installing       : glusterfs-fuse-8.4-1.el8.x86_64                                                                                  20/22 
  Installing       : python3-pyxattr-0.5.3-18.el8.x86_64                                                                              21/22 
  Installing       : glusterfs-server-8.4-1.el8.x86_64                                                                                22/22 
  Running scriptlet: glusterfs-server-8.4-1.el8.x86_64                                                                                22/22 
  Verifying        : glusterfs-8.4-1.el8.x86_64                                                                                        1/22 
  Verifying        : glusterfs-cli-8.4-1.el8.x86_64                                                                                    2/22 
  Verifying        : glusterfs-client-xlators-8.4-1.el8.x86_64                                                                         3/22 
  Verifying        : glusterfs-fuse-8.4-1.el8.x86_64                                                                                   4/22 
  Verifying        : glusterfs-server-8.4-1.el8.x86_64                                                                                 5/22 
  Verifying        : libgfapi0-8.4-1.el8.x86_64                                                                                        6/22 
  Verifying        : libgfchangelog0-8.4-1.el8.x86_64                                                                                  7/22 
  Verifying        : libgfrpc0-8.4-1.el8.x86_64                                                                                        8/22 
  Verifying        : libgfxdr0-8.4-1.el8.x86_64                                                                                        9/22 
  Verifying        : libglusterd0-8.4-1.el8.x86_64                                                                                    10/22 
  Verifying        : libglusterfs0-8.4-1.el8.x86_64                                                                                   11/22 
  Verifying        : python3-pyxattr-0.5.3-18.el8.x86_64                                                                              12/22 
  Verifying        : attr-2.4.48-3.el8.x86_64                                                                                         13/22 
  Verifying        : device-mapper-event-8:1.02.175-5.el8.x86_64                                                                      14/22 
  Verifying        : device-mapper-event-libs-8:1.02.175-5.el8.x86_64                                                                 15/22 
  Verifying        : device-mapper-persistent-data-0.8.5-4.el8.x86_64                                                                 16/22 
  Verifying        : libaio-0.3.112-1.el8.x86_64                                                                                      17/22 
  Verifying        : lvm2-8:2.03.11-5.el8.x86_64                                                                                      18/22 
  Verifying        : lvm2-libs-8:2.03.11-5.el8.x86_64                                                                                 19/22 
  Verifying        : psmisc-23.1-5.el8.x86_64                                                                                         20/22 
  Verifying        : rpcbind-1.2.5-8.el8.x86_64                                                                                       21/22 
  Verifying        : userspace-rcu-0.10.1-4.el8.x86_64                                                                                22/22 

  attr-2.4.48-3.el8.x86_64                                             device-mapper-event-8:1.02.175-5.el8.x86_64                         
  device-mapper-event-libs-8:1.02.175-5.el8.x86_64                     device-mapper-persistent-data-0.8.5-4.el8.x86_64                    
  glusterfs-8.4-1.el8.x86_64                                           glusterfs-cli-8.4-1.el8.x86_64                                      
  glusterfs-client-xlators-8.4-1.el8.x86_64                            glusterfs-fuse-8.4-1.el8.x86_64                                     
  glusterfs-server-8.4-1.el8.x86_64                                    libaio-0.3.112-1.el8.x86_64                                         
  libgfapi0-8.4-1.el8.x86_64                                           libgfchangelog0-8.4-1.el8.x86_64                                    
  libgfrpc0-8.4-1.el8.x86_64                                           libgfxdr0-8.4-1.el8.x86_64                                          
  libglusterd0-8.4-1.el8.x86_64                                        libglusterfs0-8.4-1.el8.x86_64                                      
  lvm2-8:2.03.11-5.el8.x86_64                                          lvm2-libs-8:2.03.11-5.el8.x86_64                                    
  psmisc-23.1-5.el8.x86_64                                             python3-pyxattr-0.5.3-18.el8.x86_64                                 
  rpcbind-1.2.5-8.el8.x86_64                                           userspace-rcu-0.10.1-4.el8.x86_64                                   

[root@node1 ~]# systemctl start glusterd
[root@node1 ~]# systemctl status glusterd
● glusterd.service - GlusterFS, a clustered file-system server
   Loaded: loaded (/usr/lib/systemd/system/glusterd.service; enabled; vendor preset: enabled)
   Active: active (running) since Wed 2021-04-14 13:06:39 UTC; 3s ago
     Docs: man:glusterd(8)
  Process: 10151 ExecStart=/usr/sbin/glusterd -p /var/run/ --log-level $LOG_LEVEL $GLUSTERD_OPTIONS (code=exited, status=0/SUCC>
 Main PID: 10152 (glusterd)
    Tasks: 9 (limit: 11409)
   Memory: 5.6M
   CGroup: /system.slice/glusterd.service
           └─10152 /usr/sbin/glusterd -p /var/run/ --log-level INFO

Apr 14 13:06:39 node1 systemd[1]: Starting GlusterFS, a clustered file-system server...
Apr 14 13:06:39 node1 systemd[1]: Started GlusterFS, a clustered file-system server.
[root@node1 ~]# tail -n 3 /etc/hosts glnode1 glnode2 glnode3
[root@node1 ~]# ping glnode1
PING glnode1 ( 56(84) bytes of data.
64 bytes from localhost ( icmp_seq=1 ttl=64 time=0.058 ms
64 bytes from localhost ( icmp_seq=2 ttl=64 time=0.050 ms
--- glnode1 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1016ms
rtt min/avg/max/mdev = 0.050/0.054/0.058/0.004 ms
[root@node1 ~]# mkdir -p /mnt/storage/gluster/brick
[root@node1 ~]# firewall-cmd --permanent --new-zone=glusternodes
[root@node1 ~]# firewall-cmd --permanent --zone=glusternodes --add-source=
[root@node1 ~]# firewall-cmd --permanent --zone=glusternodes --add-source=
[root@node1 ~]# firewall-cmd --permanent --zone=glusternodes --add-source=
[root@node1 ~]# firewall-cmd --permanent --zone=glusternodes --add-service=glusterfs
[root@node1 ~]# firewall-cmd --reload
[root@node1 ~]# firewall-cmd --zone=glusternodes --list-all
glusternodes (active)
  target: default
  icmp-block-inversion: no
  services: glusterfs
  forward: no
  masquerade: no
  rich rules:
[root@node1 ~]# gluster peer probe glnode2
peer probe: success
[root@node1 ~]# gluster peer probe glnode3
peer probe: success
[root@node1 ~]# gluster peer status
Number of Peers: 2

Hostname: glnode2
Uuid: ab63f0a0-0a72-4fcd-9f34-b88040d1a8e3
State: Peer in Cluster (Connected)

Hostname: glnode3
Uuid: 439ccd19-a95e-427c-ab72-6b65effcbe06
State: Peer in Cluster (Connected)
[root@node1 ~]# gluster volume create VOL1 replica 3 transport tcp glnode1:/mnt/storage/gluster/brick glnode2:/mnt/storage/gluster/brick glnode3:/mnt/storage/gluster/brick
volume create: VOL1: success: please start the volume to access data
[root@node1 ~]# gluster volume start VOL1
volume start: VOL1: success
[root@node1 ~]# gluster volume info VOL1
Volume Name: VOL1
Type: Replicate
Volume ID: 7da7bb05-2c9b-464b-b3f9-8940eeb5b0bb
Status: Started
Snapshot Count: 0
Number of Bricks: 1 x 3 = 3
Transport-type: tcp
Brick1: glnode1:/mnt/storage/gluster/brick
Brick2: glnode2:/mnt/storage/gluster/brick
Brick3: glnode3:/mnt/storage/gluster/brick
Options Reconfigured:
storage.fips-mode-rchecksum: on
transport.address-family: inet
nfs.disable: on
performance.client-io-threads: off
[root@node1 storage]# mkdir -p /mnt/VOL1
[root@node1 storage]# tail -n 1 /etc/fstab 
glnode1:/VOL1 /mnt/VOL1 glusterfs defaults,noatime,direct-io-mode=disable 0 0
[root@node1 storage]# mount /mnt/VOL1/
[root@node1 storage]# df -h
Filesystem      Size  Used Avail Use% Mounted on
devtmpfs        892M     0  892M   0% /dev
tmpfs           909M     0  909M   0% /dev/shm
tmpfs           909M  8.5M  901M   1% /run
tmpfs           909M     0  909M   0% /sys/fs/cgroup
/dev/sda1        95G  1.5G   89G   2% /
/dev/sda3       976M  148M  762M  17% /boot
tmpfs           182M     0  182M   0% /run/user/0
glnode1:/VOL1    95G  2.4G   89G   3% /mnt/VOL1
[root@node1 storage]# ls -altr /mnt/VOL1/
total 8
drwxr-xr-x. 3 root root 4096 Apr 14 13:31 .
drwxr-xr-x. 4 root root 4096 Apr 14 13:34 ..

syslog – UDP local to rsyslog and send remote with TCP and compression

This article is to show how to log Nginx’s access logs locally using UDP to the local rsyslog daemon, which will send the logs to a remote rsyslog server using TCP and compression. In general, logs could generate a lot of traffic and using UDP over distant locations could result in packet loss respectively logs’ lines loss. The idea here is to log messages locally using UDP (non-blocking way) to a local Syslog server, which will send the stream to a remote central Syslog server using TCP connections to be sure no packets are lost. In addition, we are going to enable local caching (if the remote server is temporary unreachable) and compression between the two Syslog servers.
Our goal is to use

  • UDP for our client program (Nginx in the case) for non-blocking log writes.
  • TCP between our local machine and the remote syslog server – to be sure not to lose messages on bad connectivity.
  • local caching for our client machine – not to lose messages if the remote syslog is temporary unreachable.
  • compression between the local machine and the remote syslog server.

The configuration and the commands are tested on CentOS 7, CentOS 8 and Ubuntu 18 LTS. Check out UDP remote logging here – nginx remote logging to UDP rsyslog server (CentOS 7).

STEP 1) Configure client’s local rsyslog to accept UDP log messages only if the messages’ tags are “nginx”

Couple of things should be enabled in the local client-size rsyslog daemon:

  • rsyslog to accept UDP messages. Uncomment or add the following under section “Modules” (probably the first section in the file?) in /etc/rsyslog.conf
    $ModLoad imudp
    $UDPServerRun 514


    input(type="imudp" port="514")

    The first is the old syntax, which is still supported and the second is the new syntax. For simplicity, all of the following configuration will be using the new syntax, because the old one is depricated.

  • Add a rule to catch the tag containing “nginx” and execute action to forward the messages to the remote server
    if ($syslogtag == 'nginx:') then {
    action(type="omfwd" target="" port="10514" protocol="tcp" compression.Mode="single" ZipLevel="9"
    queue.filename="forwarding" queue.spoolDirectory="/var/log" queue.size="1000000" queue.type="LinkedList" queue.maxFileSize="1g" queue.SaveOnShutdown="on"
    & stop
  • The options are almost self-explanatory, the important ones are there is no retry limit count of reconnecting to the server, there is in-disk cache of maximum 1G if the remote server is unavailable and the compression per message is turned on. More on actions, the forward module and the queue

And restart the rsyslog:

systemctl restart rsyslog

Keep on reading!

simple squid proxy with http authorization

Squid (caching) proxy has been used on the Internet for ages. The first release of Squid was back in the mid-90s!
Here is how you may use Squid as a proxy HTTP server with user and password authorization (it is easy to enable the caching, but we do not include such configuration). Our system is CentOS 7, but the configuration part is platform-independent, so just install it in your Linux distribution and use our configuration lines.

STEP 1) Install Squid

The instalation under CentOS 7

yum install squid

STEP 2) Squid configuration to use it as web caching proxy.

The configuration file is located in “/etc/squid/squid.conf” and you should add at the begging the following lines:

visible_hostname srvname
auth_param basic program /usr/lib64/squid/basic_ncsa_auth /etc/squid/pass.squid
acl ncsa_users proxy_auth REQUIRED
http_access allow ncsa_users
auth_param basic program /usr/lib64/squid/basic_ncsa_auth /etc/squid/pass.squid

Keep on reading!

nginx remote logging to UDP rsyslog server (CentOS 7)

This article will present to you all the configuration needed to remotely save access logs of an Nginx web server. All the configuration from the client and server sides is included. The client and the server use CentOS 7 Linux distribution and the configuration could be used under different Linux distribution. Probably only Selinux rules are kind of specific to the CentOS 7 and the firewalld rules are specific for those who use it as a firewall replacing the iptables. Here is the summary of what to expect:

  • Client-side – nginx configuration
  • Server-side – rsyslog configuration to accept UDP connections
  • Server-side – selinux and firewall configuration

The JSON formatted logs may be sent to a Elasticsearch server, for example. Here is how to do it – send access logs in json to Elasticsearch using rsyslog

STEP 1) Client-side – the Nginx configuration.

Nginx configuration is pretty simple just a single line with the log template and the IP (and port if not default 514) of the rsyslog server. For the record, this is the official documentation In addition it worth mentioning there could be multiple access_log directives in a single section to log simultaneously on different targets (and the templates may be different or the same). So you can set the access log output of a section locally and remotely.
Nginx configuration (probably /etc/nginx/nginx.conf or whatever is the organization of your Nginx configuration files.)

server {
     access_log      /var/log/nginx/example.com_access.log main;
     access_log      syslog:server=,facility=local7,tag=nginx,severity=info main3;

The “main” and “main3” are just names of the logging templates defined earlier (you may check rsyslog remote logging – prevent local messages to appear to see an interesting Nginx logging template).
The error log also could be remotely logged:

error_log syslog:server= debug;

STEP 2) Server-side – rsyslog configuration to accept UDP connections.

Of course, if you have not installed the rsyslog it’s high time you installed it with (for CentOS 7):

yum install -y rsyslog

To enable rsyslog to listen for UDP connections your rsyslog configuration file (/etc/rsyslog.conf) must include the following:

$ModLoad imudp
$UDPServerRun 514

Most of the Linux distributions have these two lines commented so you just need to uncomment them by removing the “#” from the beginning of the lines. If the lines are missing just add them under section “MODULES” (it should be near the first lines of the rsyslog configuration file).
Change the 514 with the number you like for the UDP listening port.
Write the client’s incoming lines of information to a different location and prevent merging with the local log messages – rsyslog remote logging – prevent local messages to appear. Include as a first rule under the rules’ section starting with “RULES” of the rsyslog configuration file (/etc/rsyslog.conf):

# Remote logging
$template HostIPtemp,"/mnt/logging/%FROMHOST-IP%.log"
if ($fromhost-ip != "" ) then ?HostIPtemp
& stop

Logs only of remote hosts are going to be saved under /mnt/logging/.log.
Keep on reading!