increase tmp Filesystem online with out reboot in Solaris

APPLIES TO : Solaris 10

ISSUE : The /tmp was configured to 512MB mount and it's exceeded and unfortunately that server cannot be rebooted or the /tmp cannot be umounted (bunch of files were opened and used). OR the mount_tmpfs doesn't support the "remount" option ("mount -F tmpfs -o remount /tmp")

GOAL :  Increase /tmp FS space online with out reboot the Solaris 10 server.

SOLUTION :  Increase the /tmp to 3GB

This example shows how I grew the 512MB mounted /tmp to 3GB on a Solaris 10 8/11 u10 SPARC system. 

Please, don't try this in your system. If you don't listen to me then keep in mind that the HEXA numbers might differ on your system.


EXAMPLE :  

1.      Get the relevant info of the /tmp
                JUDI-DEV-001 # df -h /tmp
                Filesystem             size   used  avail capacity  Mounted on
                swap                   512M   152K   512M     1%    /tmp
                JUDI-DEV-001 #


                JUDI-DEV-001 # echo "::fsinfo" | mdb -k | egrep "VFSP|/tmp"
                            VFSP FS              MOUNT
                0000060019aaea80 tmpfs           /tmp
                JUDI-DEV-001 #

2.      Get the address of the tm_anonmax to set its value.
                JUDI-DEV-001 # echo "0000060019aaea80::print vfs_t vfs_data | ::print -ta struct tmount tm_anonmax" | mdb -k
                600167d0810 ulong_t tm_anonmax = 0x10000
                JUDI-DEV-001 #
        // Address and the current value of the tm_anonmax

3.      Set the new value
                JUDI-DEV-001 # echo "600167d0810/Z 0x60000" | mdb -kw
                0x600167d0810:  0x10000                 =       0x60000
                JUDI-DEV-001 #
                NOTE: the 0x60000 is 384KB -> 384KB * 8KB = 3072MB = 3GB.



4.      Check if it's set.
                JUDI-DEV-001 # echo "600167d0810/J" | mdb -k
                0x600167d0810:  60000
                JUDI-DEV-001 #

        OR
                JUDI-DEV-001 # echo "60019aaea80::print vfs_t vfs_data | ::print struct tmount tm_anonmax" | mdb -k
                tm_anonmax = 0x60000
                JUDI-DEV-001 #



5.      Check if it's working or not.
                JUDI-DEV-001 # df -h /tmp
                Filesystem             size   used  avail capacity  Mounted on
                swap                   3.0G   152K   3.0G     1%    /tmp

                JUDI-DEV-001 #

This modification will not exists post reboot, After reboot of  server the default configured tmp size (512MB) will get mounted, Please make sure to change the /etc/vfstab entry. with a - instead of 512 for /tmp

CONCLUSION : 
The Live Example above shows a real example which was done by myself on a Sol10 system.
I think this solution above can be done on any Solaris version which has the feature of the tmpfs-ed /tmp Filesystem


Credits and More details :-
http://ilapstech.blogspot.com/2009/11/grow-tmp-filesystem-tmpfs-on-line-under.html




~Judi~