Article ID: 120121, created on Feb 14, 2014, last review on Feb 15, 2016

  • Applies to:
  • Virtuozzo
  • Virtuozzo containers for Linux
  • Virtuozzo hypervisor

Symptoms

A container migration attempt fails with the following errors:

vztar : /bin/vztar: -: Cannot write: Connection reset by peer
vztar : /bin/vztar: Error is not recoverable: exiting now
/bin/vztar exited with code 2

or

1391783367: Copy private area '/vz/private/1017' 
1391783367: write() : Broken pipe 
1391783367: vzsock_send() return 5 
1391783367: Can't move/copy CT#101 -> CT#101, [], [] : vzsock_send() return 5

The container has a large amount of inodes inside.

Cause

The allowed SSH or TCP inactivity period is insufficient and doesn't allow the migration to complete.

Resolution

Enable SSH client keep-alive probes on the source server:

# grep Alive /etc/ssh/ssh_config
    ServerAliveInterval 100
    ServerAliveCountMax 100

Sometimes TCP keep-alive settings should be adjusted on both source and destination nodes too.

tcp_keep-alive_time should be the same on both nodes, and it should be less than TCP timeout configured on the Hardware Firewall. This will instruct the nodes to start keep-alive communication before Hardware Firewall timeout.

For example, if the Hardware Firewall is configured with 10 minutes TCP timeout, send the keep-alive probes every 9 minutes:

[root@vz ~]# echo 540 > /proc/sys/net/ipv4/tcp_keepalive_time

To increase the keep-alive duration:

[root@vz ~]# echo 100 > /proc/sys/net/ipv4/tcp_keepalive_probes
[root@vz ~]# echo 100 > /proc/sys/net/ipv4/tcp_keepalive_intvl

The value of tcp_keepalive_probes should be chosen depending on the application needs. 100 keep-alive packets with 100 seconds interval will result in more than two and a half hours of a live connection, which should be sufficient for most cases.

Note: correct /etc/sysctl.conf to make these changes permanent.

net.ipv4.tcp_keepalive_time = 540
net.ipv4.tcp_keepalive_probes = 100
net.ipv4.tcp_keepalive_intvl = 100

Note: the default keep-alive values are:

# cat /proc/sys/net/ipv4/tcp_keepalive_time
7200
# cat /proc/sys/net/ipv4/tcp_keepalive_intvl
75
# cat /proc/sys/net/ipv4/tcp_keepalive_probes
9

Search Words

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