CMCDragonkai's questions

I have a situation where I need to create 100s of thousands of 0 byte lock files for concurrency control.

I've tested creating them by using:

for i in `seq 1 50000`; do touch "/run/lock/${i}.lock"; done

Since the files are 0 bytes, they don't up any space in the partition. Looking at df -h:

Filesystem      Size  Used Avail Use% Mounted on
tmpfs            50M  344K   49M   1% /run
none            5.0M     0  5.0M   0% /run/lock
none            246M     0  246M   0% /run/shm
none            100M     0  100M   0% /run/user

The 0% figure doesn't change at all in the /run/lock row.

However the memory size does increase at an average of approximately 1KB per lock file. I discovered this by comparing free -h before and after creating 70,000 lockfiles inside /run/lock. This memory increase was reflected in real memory usage (virtual memory minus the buffers/cache).

Later I discovered that this 1KB increase is most likely due to the inodes. So I checked inode usage using df -i:

Filesystem      Inodes  IUsed   IFree IUse% Mounted on
tmpfs            62729    322   62407    1% /run
none             62729  50001   12728   80% /run/lock
none             62729      1   62728    1% /run/shm
none             62729      2   62727    1% /run/user

As you can see, the lockfiles increase inodes inside the /run/lock partition.

I'm currently on Ubuntu and the /run mounts are not reflected inside /etc/fstab. Running mount gives me:

tmpfs on /run type tmpfs (rw,noexec,nosuid,size=10%,mode=0755)
none on /run/lock type tmpfs (rw,noexec,nosuid,nodev,size=5242880)
none on /run/shm type tmpfs (rw,nosuid,nodev)
none on /run/user type tmpfs (rw,noexec,nosuid,nodev,size=104857600,mode=0755)

I have a couple questions regarding this (but the first one is the most important):

1. How do I increase the inode limit permanently for /run/lock? So that this limit survives restarts?
2. Would it be better off for me to create my own directory and mount tmpfs on it to use for this instead of using /run/lock?
3. Is each partition's size limit completely independent from each other? That is storing files in /run doesn't seem to affect /run/lock and vice versa.
4. Is the 1KB derived from the inode? I noticed that when creating non-empty files, the basic block is 4KB for each file.
5. Why is /run given the filesystem type of tmpfs but /run/lock, /run/shm, /run/user give filesystem type of "none", especially since all of them are backed by TMPFS? Why aren't they all read as tmpfs in the Filesystem column?
6. If all of the directories are independently constrained, how does the OOM killer handle in a situation where there are multiple full TMPFS partitions, each of them sized to 50% of the RAM, and where there are also processes contending for RAM as well. Obviously one cannot use over 100% of RAM. According to the https://www.kernel.org/doc/Documentation/filesystems/tmpfs.txt it mentions the system will deadlock. How does that work?

I'm using the /etc/cron.d/ folder to store my cron tasks. These tasks are symlinks to my actual file which is kept under VCS. These files are owner by a user named "www-data". I've read that Cron will not run tasks that are under a different owner. (http://klenwell.com/press/2010/11/cron-d/) So how can I make Cron run the cron tabs under a different owner from root? I don't want to change the owner to root, as all these files in this folder is owner by "www-data".

I'm confused by this ini list in the PHP Manual: http://www.php.net/manual/en/ini.list.php

I want to set some custom php.ini values through htaccess, but which one of these commands is not going to work?

php_value upload_max_filesize 1M

php_value max_execution_time 3

php_value max_input_time 3

php_value memory_limit 2M

php_value post_max_size 1M

php_value open_basedir "/scripts"

php_flag allow_url_fopen 0

php_flag allow_url_include 0

php_flag file_uploads 0

php_value disable_functions 'apache_child_terminate, apache_setenv, define_syslog_variables, escapeshellarg, escapeshellcmd, exec, fp, fput, ftp_connect, ftp_exec, ftp_get, ftp_login, ftp_nb_fput, ftp_put, ftp_raw, ftp_rawlist, highlight_file, ini_set, phpinfo, ini_alter, ini_get_all, ini_restore, inject_code, mysql_pconnect, openlog, passthru, php_uname, phpAds_remoteInfo, phpAds_XmlRpc, phpAds_xmlrpcDecode, phpAds_xmlrpcEncode, popen, posix_getpwuid, posix_kill, posix_mkfifo, posix_setpgid, posix_setsid, posix_setuid, posix_setuid, posix_uname, proc_close, proc_get_status, proc_nice, proc_open, proc_terminate, shell_exec, syslog, system, xmlrpc_entity_decode, curl_exec, curl_multi_exec, parse_ini_file, show_source, pcntl_fork, pcntl_exec, session_start, getmyuid, getmypid, leak, listen, diskfreespace, tmpfile, link, fopen, unlink, mkdir, file_get_contents, file, fread, rmdir, readfile, file_put_contents, fwrite, delete, fscanf, ignore_user_abort, dl'