While using df

df -h is the command to display available disk free space in bytes


e.g.,

$df -h

Filesystem size used avail capacity Mounted on

/dev/md/dsk/d84 3.9G 136M 3.8G 4% /var

swap 6.6G 992K 6.6G 1% /tmp

/dev/md/dsk/d101 20G 7.8G 12G 41% /software

Equivalent df in AIX

df -g

Truss
truss is a command to trace system calls and signals


SYNOPSIS

truss [-fcaeildDE] [- [tTvx] [!] syscall ,...]

[- [sS] [!] signal ,...] [- [mM] [!] fault ,...]

[- [rw] [!] fd ,...]

[- [uU] [!] lib ,... : [:] [!] func ,...]

[-o outfile] command
-p pid[/lwps]...

DESCRIPTION

The truss utility executes the specified command and produces a trace ofthe system calls it performs, the signals it receives, and the machine faults it incurs. Each line of the trace output reports either the fault or signal name or the system call name with its arguments and return value(s).

System call arguments are displayed symbolically when possible using defines from relevant system headers. For any path name pointer argument, the pointed-to string is displayed.

Error returns are reported using the error code names described in intro(3). If, in the case of an error, the kernel reports a missing privilege, a privilege name as described in privileges(5) is reported in square brackets ([

]) after the error code name.

Optionally (see the -u option), truss also produce an entry/exit trace of user-level function calls executed by the traced process, indented to indicate nesting.

Why to know about truss?

In the day today admin job, you may want to see what a process is doing? or you may want to check an installation process. Or ur installation process is failing, you want check whats going on. You use truss in such conditions.

Some examples:

truss -p pid

gives you that specific pids systemcalls

$ truss -p 883

/14: lwp_cond_wait(0x0193BFF8, 0x0193BFE0, 0xD287F710, 0) Err#62 ETIME

/14: lwp_cond_broadcast(0x016BA688) = 0

/14: lwp_cond_broadcast(0x01299A98) = 0

/205: lwp_cond_wait(0x016BA688, 0x016BA670, 0xD187F748, 0) = 0

/205: lwp_cond_broadcast(0x0193BFF8) = 0

/14: lwp_cond_wait(0x0193BFF8, 0x0193BFE0, 0x00000000, 0) = 0

/205: lwp_mutex_wakeup(0x0193BFE0) = 0

/14: lwp_mutex_timedlock(0x0193BFE0, 0x00000000) = 0

/205: lwp_mutex_wakeup(0x000F8AD8) = 0

/14: lwp_mutex_timedlock(0x000F8AD8, 0x00000000) = 0

/14: lwp_cond_broadcast(0x000D2E80) = 0

/205: stat64("/software/IBM/WebSphere/AppServer/profiles/AppSrv01/installedApps/hornblowerNode01Cell/FRPApp.ear/FRPApp-WebModule.war/WEB-INF/classes/us/ny/state/oag/model/OrganizationDetail.class", 0xD187F628) = 0


883 is a WebSphere pid.


$ truss -o example.out -p 883

truss traces pid 883 and outputs to example.out

$truss -o example.out install.sh

install.sh is an installer of a software. truss traces the installation process's system calls and outputs to example.out

Umask
umask stands for user file creation mode mask.


777 stands for rwxrwxrwx. first set of rwx is for user, second set of rwx for group and last set is for others. to know what umask u have, at the prompt type umask, which will return a value, say 022.

What does that mean o22?

Its simple.

777-022=755.

umask 022 = rwxr-xr-x, meaning, user has all permissions, group has read and execute, others have read and execute.

To understand umask in permissions mode try this command, umask -S

for example

$ umask

022

$ umask -S

u=rwx,g=rx,o=rx