Error message on user interface session_start(): open(/var/lib/php/sessions

[zabbix-tech]

Hello everyone,
After restarting the Zabbix server (unplanned). For several days I got an error message on the zabbix user interface. Do you have any idea how to solve this problem?
Please see screenshot !
Thank you !

This is the error message:

• session_start(): open(/var/lib/php/sessions/sess_oj700tkhgfdeoopvtbfki56h07, O_RDWR) failed: Read-only file system (30) [zabbix.php:21 → require_once() → ZBase->run() → ZBase->processRequest() → CControllerWidgetSystemView->__construct() → CController->__construct() → CSession::start() → session_start() in include/classes/core/CSession.php:49]
• session_write_close(): open(/var/lib/php/sessions/sess_oj700tkhgfdeoopvtbfki56h07, O_RDWR) failed: Read-only file system (30) [zabbix.php:21 → require_once() → ZBase->run() → ZBase->processRequest() → CControllerWidgetSystemView->__construct() → CController->__construct() → CSession::start() → session_write_close() in include/classes/core/CSession.php:53]
• session_write_close(): Failed to write session data (files). Please verify that the current setting of session.save_path is correct (/var/lib/php/sessions) [zabbix.php:21 → require_once() → ZBase->run() → ZBase->processRequest() → CControllerWidgetSystemView->__construct() → CController->__construct() → CSession::start() → session_write_close() in include/classes/core/CSession.php:53]
• session_start(): open(/var/lib/php/sessions/sess_oj700tkhgfdeoopvtbfki56h07, O_RDWR) failed: Read-only file system (30) [zabbix.php:21 → require_once() → ZBase->run() → ZBase->processRequest() → CController->run() → CControllerWidget->checkInput() → CController->validateInput() → CSession::keyExists() → CSession:pen() → session_start() in include/classes/core/CSession.php:138]
• session_write_close(): open(/var/lib/php/sessions/sess_oj700tkhgfdeoopvtbfki56h07, O_RDWR) failed: Read-only file system (30) [zabbix.php:21 → require_once() → ZBase->run() → ZBase->processRequest() → CController->run() → CControllerWidget->checkInput() → CController->validateInput() → CSession::keyExists() → CSession::close() → session_write_close() in include/classes/core/CSession.php:149]
• session_write_close(): Failed to write session data (files). Please verify that the current setting of session.save_path is correct (/var/lib/php/sessions) [zabbix.php:21 → require_once() → ZBase->run() → ZBase->processRequest() → CController->run() → CControllerWidget->checkInput() → CController->validateInput() → CSession::keyExists() → CSession::close() → session_write_close() in include/classes/core/CSession.php:149]

[dimir]

As already told here https://support.zabbix.com/browse/ZBX-16832, the error message clearly states that the file system the frontend is trying to write session file to is read-only. This can happen, e. g. in case of disk errors. Check syslog, fix the issue and re-mount the filesystem rw.
If you do not understand the issue I suggest turning to a system administrator that maintains the host the frontend is installed.

[zabbix-tech]

Here are the manipulations I did on the zabbix server:

- Check the partition files with the “mount” command, we saw this error:
/dev/mapper/INFRA–ZBX–001–vg-root on / type ext4 (rw,relatime,errors=remount-ro,data=ordered)
and
/dev/mapper/zbx_db on /var/lib/mysql type ext4 (rw,noexec,noatime,nodiratime,errors=remount-ro,data=ordered)

- Reboot the server in single mode and run the fsck command on the system
- We try also a FSCK in recovery mode with Debian.

The problem always there.

We try also a another tips:

• Stop zabbix service
• Stop apache2 service
• move the profile in another old folder /var/lib/php/sessions/sess_gdep7c5m45djkqrk0iadmjep64
• Start zabbix service
• Start apache2 service

The problem is not resolve…

[dimir]

How exactly do you check current mode for the filesystem? And are you checking it on the host your frontend is running on?
Once again, a command to check how the filesystem is mounted currently is:

grep " $(df -k --output=target /var/lib/php | sed 1d) " /proc/mounts

If you see something like

/dev/mapper/INFRA–ZBX–001–vg-root on / type ext4 (ro,relatime,errors=remount-ro,data=ordered)

(note, the first ro in the braces) your filesystem is re-mounted read-only, check syslog for errors.

[seanwasere]

I had the same error,
Zabbix Server 4.4.4, Centos7, Nginx

These 2 commands fixed it for me.

grep AVC /var/log/audit/audit.log* | audit2allow -M systemd-allow; semodule -i systemd-allow.pp

chown -R apache:apache /var/lib/php/

I thought maybe a yum update caused something to change, but I couldn't reproduce it on a different server with same specs. So ?

[dimir]

Yes, another option could be SELinux.

[g00fy]

To me this same error message happened on Zabbix 6.4.8 & PHP 8.2.
Within the global PHP configuration in /etc/php/8.2/apache2/conf.d/file.ini I had `session.auto_start = 1` set.

But then these warnings appeared in the logs:
```
PHP Warning: ini_set(): Session ini settings cannot be changed when a session is active in /usr/share/zabbix/include/classes/core/CCookieSession.php on line 37
PHP Warning: session_set_save_handler(): Session save handler cannot be changed when a session is active in /usr/share/zabbix/include/classes/core/CCookieSession.php on line 39
```

As well as the "Session initialization error" error on the php zabbix frontend that got me to this thread in the first place.

As I upgraded from php 7 -> 8, within my virtual host file of apache I had something like "ifmodule php7". So I removed the "ifmodule" tags and added "php_value session.auto_start 0".
apache2 restart & everything was fine once more.

HTH someone