My server don't save the session

[OsaMasw]

Hey there guys, I have a strange problem, I have many linux servers (ubuntu) I have a script installed on them
all servers works fine but one server dont keep login information, everytime I logged in its says hello to server then back to previous page wothout logging in, I've checked many artcles n internet about sessions save path and it was /tmp like ohter servers
I've checked the permession for folder /var/lib/php5 and its writeable
what can I do to solve this problem, no one on this server can login.

[OsaMasw]

I found my Space is nearly full is that affect ? and how to reduce it ?

[OsaMasw]

I found a file in /var/log/upstart called mysql.log.1 with size 40GB is it safe to delete it ?

[pritaeas]

See what it contains. If it's the (slow) query log, and you have a backup, it will be safe to delete.

[cereal]

Also mysql.log.1 is not the current log file, it's an old copy, so it can be moved to another location for further analysis or deleted, the main in use is mysql.log. Since it's a general log you can stop it, by commenting the line related to the general_log_file.
Just enable: error.log, mysql-slow.log and expires_logs_days, so you can limit the amount of data. To edit these options run:

sudo editor_of_choice /etc/mysql/my.cnf

Example settings:

#general_log_file        = /var/log/mysql/mysql.log
#general_log             = 1
log_error = /var/log/mysql/error.log
log_slow_queries = /var/log/mysql/mysql-slow.log
long_query_time = 2
log-queries-not-using-indexes
expire_logs_days = 10

Reload mysql after you've done.

[OsaMasw]

every thing solved by deleting this file, and thanks for the tips about expire_logs_days