Under certain condition depending on the system configuration, NoMachine connections fail to start after some hours of normal activity. In similar cases a restart of nxserver helps, but the problem re-occurs later.

Users receive message  “The connection with the server was lost” and the nxserver.log file reports:

Error is: 24, 'Too many open files'

Message  "Too many open files" is generally not a NoMachine issue, but a topic of operating system configuration.

Both nxserver and nxnode have around 50 open files per session.

For one active session, lsof(8) tells:

# lsof | grep nxserver | wc -l
45
# lsof | grep nxnode | wc -l
49

The nx server runs under the UID of the nx user, nxnode runs under the UID of the user invoking the session.

For the nx user, the default limit of 1024 is surpassed with 23 sessions.

To increase the allowed number of open files, add the following lines to /etc/security/limits.conf:

nx               soft    nofile           65535
nx               hard    nofile           65535

Change 'nx' to '*' if you want to give the above limits to all users.

To view the number of overall open files on the system and their limits, use the following commands:

# lsof | wc -l
# cat /proc/sys/fs/file-max

To increase the system limits, run

# echo 16777216 > /proc/sys/fs/file-max

To make the changes permanent, edit /etc/sysctl.conf and add the line

fs.file-max = 16777216

To reload /etc/sysctl.conf, run the command

sysctl -p /etc/sysctl.conf