Clean Up Ebooks Catalog
Plans change, companies shift focus, and people move on. At some point, every admin has had to clean up shell access after someone has left the company, happily or otherwise. When you do have to lock old accounts up, it's best to proceed strategically. Don't assume that just because you ran a passwd -I that the user in question can't regain access to your machine. Let's assume that we're locking up after an account called luser. Here are some obvious (and some not so obvious) things to check on in the course of cleaning up
After your initial installation of an Ubuntu release, Ubuntu keeps downloaded packages cached in var cache apt to speed up downloading if you ever need them again. This can eventually use up a lot of disk space. You can remove this package cache, but you will need to download a removed package again at a later date if it is needed for dependencies. Clean up the cache by giving apt-get the clean option. We show how this works by first running the Linux find command on the var cache apt directory to show the packages currently cached Now clean up all the packages cached in the APT cache directory, and then verify that they are removed by running the find command again
If you're using a child process simply to exec another program, it's fine to call wait immediately in the parent process, which will block until the child process completes. But often, you'll want the parent process to continue running, as one or more children execute synchronously. How can you be sure that you clean up child processes that have completed so that you don't leave zombie processes, which consume system resources, lying around One approach would be for the parent process to call wait3 or wait4 periodically, to clean up zombie children. Calling wait for this purpose doesn't work well because, if no children have terminated, the call will block until one does. However, wait3 and wait4 take an additional flag parameter, to which you can pass the flag value WNOHANG. With this flag, the function runs in nonblocking mode it will clean up a terminated child process if there is one, or simply return if there isn't.The return value of the call is the process ID of the terminated...
If you do not have sufficient free space to install SUSE Linux and YaST cannot automatically resize your existing operating system partitions, your only alternative (besides adding another disk to your system) is to abort the SUSE install process, remove the installation media, and reboot into your other operating system. You must then free up sufficient disk space and clean up the organization of your operating system's partition(s) using a utility such as Windows' Disk Defragmenter. If there is sufficient unused space on your Windows partition, you should be able to restart the SUSE installation process and let YaST select appropriate partitioning and resizing values for you.
It is always a good idea to run apt get clean when inside the chroot and before exiting to clean up space in the var cache apt archives directory. Indeed the preceding script does this. This is because space is at a premium. Another idea is also to install deborphan and or gtkorphan in order to remove unused programs and libraries that are taking up space (apt-get install deborphan).
A task that needs to be performed on a regular basis is cleaning up the file system. For this purpose, you can use the rm command. For example, use rm tmp somefile to remove somefile from the tmp directory. If you are root and have all the proper permissions on the file, you will succeed without any problems. (See Chapter 6 for more about permissions.) Since removing files can be delicate (imagine removing the wrong files), it may be necessary to push the rm command a little. You can do this by using the -f (force) switch. For example, use rm -f somefile if the command complains that somefile cannot be removed.
We've never encountered a case where we te- -a didn't want to re-create folders. If you don't select the Re-create Folders check box, all the subdirectories and their contents end up in your current directory. Cleaning up the unpacked pile of structureless files wastes time.
If the Message from banner appears on your screen and obscures something you are working on, press CONTROL-L or CONTROL-R to refresh the screen and remove the banner. Then you can clean up, exit from your work, and respond to the person who is writing to you. You have to remember who is writing to you, however, because the banner will no longer appear on the screen.
The tmpwatch utility recursively searches through specified directories and removes files which have not been accessed in a specified period of time. Tmpwatch is normally used to clean up directories which are used for temporarily holding files (for example, tmp). Tmpwatch ignores symlinks, won't switch filesystems and only removes empty directories and regular files.
We use this function just like the previous example using the dots function in Listing 4.2. We start the function in the background, save the PID of the background function using the operator, start our time-consuming task, and kill the background rotate function when the task is complete. We could also just put the while loop in the background without using a function. In either case, when the rotating line is killed, we need to clean up the last characters on the screen. To do the cleanup we just back up the cursor and overwrite the last character with a blank space. (See Listing 4.4.)
Working with soft and hard limits is confusing at first but has some advantages. If a user has more data than the soft limit allows, the user still can create new files and isn't stopped from working immediately. The user will, however, get a warning about needing to clean up files, because when the hard limit is reached, no more new files can be created whatsoever.
Another good practice is to scan user areas for users with large disk usage. Tell those users to clean up their areas by deleting or archiving material they don't want or need. In many cases, users keep multiple copies of files around, just in case. Remove the old ones Get rid of automatic backup files, and clean out large log files. Just cleaning out the system logs can free up 30M on some systems. The primary log files you should look at are the following Next, get in the habit of routinely backing up material you don't need except as archive material. Use floppy disks, a tape drive, or other archive material and stick the data on the shelf instead of on your hard drive. You'll save lots of room by regularly going through your system and cleaning up files. If you really need to keep them on your hard disk, use compress or gzip to shrink the file size noticeably. To find all files that haven't been accessed (read or write) in a certain number of days, use the find command. This...
Cleaning up is an essential part of running a secure and efficient system. You can use resources most efficiently if your system doesn't have an abundance of unused services hanging around in the background, tying up CPU time. Unnecessary services are also an invitation to hackers. Can hackers exploit an open port you've forgotten about In this technique, we explain the best ways to avoid these pitfalls by t Getting rid of old users' stuff Old files are another waste of resources why take up good disk space for outdated data When users move on and you clean up, be sure to remove all their old files otherwise, you're just wasting space by storing data that's unlikely to be used again. i Cleaning up after ex-users
The option to deinstall a package with broken control scripts does not really exist when a package's removal scripts are the ones causing problems. Even though you could force the removal by causing the offending control script to exit cleanly, this would prevent dpkg from cleaning up your system properly, potentially leaving orphaned files behind. Short of fixing the problem (and submitting a patch to the bug tracking system), it is probably best to report the problem (see chapter 10.6) and wait for an updated, fixed version to percolate into the archive. Then, the package may be removed as it should. This only holds for the postrm script, however. If the prerm script is broken, you will have to simulate its successful completion to make the upgrade to the next package version work.
The SIGTERM signal can be handled by processes in that it allows processes to clean up before exiting for example, the process may want to close the files it has opened before exiting. If the safer option of SIGTERM does not work, then we may resort to SIGKILL. The SIGKILL signal forces a process to terminate immediately - it does not allow it to exit gracefully. The man 7 signal command lists and describes the complete set of signals.
When called, it causes abnormal program termination, so the usual clean-up tasks, such as closing files, and any functions registered with atexit() do not exit() is abort() 's civilized cousin. Like abort(), it terminates a program and returns a value to the OS, but, unlike abort(), it does so only after doing any clean up and, if you have additional clean up performed by functions registered with atexit(), it calls them as well. status returns the exit value to the operating system. Any integer value is legal, but only EXIT_SUCCESS and EXIT_FAILURE, defined in , and 0 are portable return values. Many, if not most, of the programs you have already seen in this book use it. See line 8 of Listing 13.5, for example.
When you download a file using Firefox, the download is managed by the Download Manager. You can download several files at once. Progress can be displayed in the Download Manager window, accessible from the Tools menu. You can cancel a download at any time, or just pause a download, resuming it later. Right-clicking a download entry will display the site it was downloaded from, as well as the directory you saved it in. To remove an entry, click Remove. To clear out the entire list, click Clean Up.
X startup scripts may include calls to other programs beyond window managers or desktop environments. For instance, if you want to launch an xterm when you log in, you would include a line that calls this program prior to the window manager call. Such calls typically end in ampersands (&) to launch the program in the background otherwise, the script will stop executing until the program terminates. The call to the window manager, by contrast, lacks this feature this way, the script doesn't continue executing until you exit from the window manager. After that point, X shuts down or your XDMCP server's login window reappears. On occasion, an X login script includes a few lines after the window manager call. These lines may clean up temporary files, play a logout sound, or what have you. Listing 9.2 shows a typical X login file. This file launches an xterm and plays a login sound before launching the IceWM window manager. (IceWM manages the xterm, even though the xterm was launched...
The next line in the inittab file instructs init to execute the etc rc.d rc.sysinit script before entering the default run level. This script performs many initialization routines such as choosing a keymap file, checking and mounting root and proc file systems, setting the clock and hostname, configuring swap space, cleaning up temp files, and loading modules.
To control remote terminals not using XDMCP, xdm searches the window hierarchy on the display and uses the protocol request KillClient in an attempt to clean up the terminal for the next session. This may not actually kill all of the clients, as only those which have created windows will be noticed. XDMCP provides a more sure mechanism when xdm closes its initial connection, the session is over and the terminal is required to close all other connections.
Security problems aren't restricted to servers. Non-server programs are also often flawed. If your system has multiple users, these bugs can be exploited to gain root access. The fact that the compromise is local in origin doesn't simplify your task you must clean up the problem, most likely
In Chapter 4, we introduced the Synaptic Package Manager when we learned how to clean up residual config packages and orphaned packages. This same tool can be used to install software much as you did with the Add Remove tool. By navigating to System Administration Synaptic Package Manager, you can launch another graphical user interface that allows you to install and uninstall software applications. Like the Add Remove tool, Synaptic will ask you for your password and then open into a window as seen in Figure 6-3.
You can change the prompt in your current terminal (using the example elite function above) by typing source elite followed by elite (assuming that the elite function file is the working directory). This is somewhat cumbersome, and leaves you with an extra function (elite) in your environment space - if you want to clean up the environment, you would have to type unset elite as well. This would seem like an ideal candidate for a small shell script, but a script doesn't work here because the script cannot change the environment of your current shell it can only change the environment of the subshell it runs in. As soon as the script stops, the subshell goes away, and the changes the script made to the environment are gone. What can change environment variables of your current shell are environment functions. The bashprompt package puts a function called callbashprompt into your environment, and, while they don't document it, it can be called to load any bashprompt theme on the fly. It...
We've mentioned already that the protection offered by Linux when working as a normal user is a definite advantage. Certainly, working as root all the time is one of the worst habits that a novice Linux user can develop. For example, suppose you're working as the root user, and you're cleaning up some unwanted files in your home directory, so you want to execute the following command
Beyond the loop, there is just a bit of cleaning up to do. The current state is set to TASK_RUNNING to reflect the fact that we are no longer asleep this is necessary because if we exited the loop without ever sleeping, we may still be in TASK_INTERRUPTIBLE. Then remove_wait_queue is used to take the process off the wait queue.
The fourth area, resource management, is essentially responsible for the starting, stopping, and cleaning up after jobs that are run on cluster nodes. In a batch system resource management involves running a job for a user, under the identity of the user, on the resources the user was allocated in such a way that the user need not be present at that time.
We are adding something new to this example program a quit button. We could simply call exit, but it is better to clean up any references to shared X resources by first calling XtDestroyApplicationContext. In this example, we declare the application context as a global variable so that the do_quit Callback function has access to application context
The purpose of make is to bring a software project up to date. At every step of a project, make identifies and executes the actions required to bring a project to a known state which sources to recompile for an up-to-date executable, which executables to rebuild for an up-to-date project, which files to remove to clean up your project area, and so on.
You can check out ongoing development of the RPM from the RPM project site (http rpm.org). Fedora 10 includes a major upgrade to RPM 4.6. Improvements in RPM 4.6 include features to provide support for larger files, better compression, improved architecture dependency, and better clean-up of stale lock files. For end users, these improvements should result in better reliability, security and performance.
All Condor jobs have two methods for preemption graceful and quick. Standard Universe jobs are given a chance to produce a checkpoint with graceful preemption. For the other universes, graceful implies that the program is told to get off the system, but it is given time to clean up after itself. On all flavors of Unix, a SIGTERM is sent during graceful shutdown by default, although users can override this default when they submit their job. A quick shutdown involves rapidly killing all processes associated with a job, without giving them any time to execute their own cleanup procedures. The Condor system performs checks to ensure that processes are not left behind once a job is evicted from a given node.
* Perform the transfer and clean up. * status spull_transfer(device, CURRENT) spin_unlock_irqrestore(&device- lock, flags) The interrupt handler has a couple of tasks to perform. First, of course, it must check the status of the outstanding transfer and clean up the request. Then, if there are further requests to be processed, the interrupt handler is responsible for getting the next one started. To avoid code duplication, the handler usually just calls the request function to start the next transfer. Remember that the request function expects the caller to hold the io_request_lock, so the interrupt handler will have to obtain it. The end_request function also requires this lock, of course.
If the message type is not one of these two, we clean up the memory allocated and return an error indicating we don't know how to handle whatever PAM has given us with PAM_CONV_ERR. Note that the result of our actions is stored in the response array we allocated previously, ordered identically to that of the requests.
SWT breaks some of the Java contract. For example, you cannot rely on garbage collectionto clean up SWT objects. Any SWT object you create with new must be explicitly destroyed with a call to thedispose() method. Why Since SWT is implemented with native methods, the low-level implementation allocates native OS data structures and objects that must be explicitly freed. Since the Java garbage collector cannot be relied upon to collect objects at a certain time (or ever, for that matter), these allocations can result in memory leaks and address space conflicts. As we shall see, however, SWT is well designed to minimize the amount of this that you need to worry about.
You can find out what processes are holding a file system open using the fuser command (for example, fuser -v home). If you can't close those processes gracefully (which is preferred), you can kill them all immediately using the -k option (for example, fuser -k home). If an NFS file system still won't unmount, you can force unmount it (umount -f mnt maple) or unmount and clean up later (umount -l mnt maple). The -l option is usually the better choice because a forced unmount can disrupt a file modification that is in progress.
Many cache files, you can use these tags to start cleaning up files automatically. For this process, you use a least recently used algorithm if an item is sitting in cache and hasn't been used for a long time, it will be removed first. The cache_swap_low tag, which is set to 90 percent by default, defines when the file cleanup should start, and the cache_swap_high tag defines when file cleanup should start to happen more aggressively.
The ADD instruction at the end of the sequence represents what you'll hear described as ''cleaning up the stack.'' Each time we push something onto the stack with a push instruction, the stack pointer ESP moves toward low memory Not well If you forget to clean up the stack, or if you clean it up by the wrong number of bytes, your program will almost certainly throw a segmentation fault. Details dare I call it neatness count
Of these commands, the first two just clean up the current configuration and pass to your current environment the variables you've set in etc openvpn easy-rsa vars. The latter command generates the CA for you. Listing 12-2 gives an example of the output of these commands.
Let's start at the Beginning of Main in Listing 20.9. The very first thing that we do is set a trap. This trap is set for exit codes 1, 2, 3, 5, and 15. On any of these captured signals the cleanup function is executed, and then the shell script exits with a return code of 1. It is nice to be able to clean up before the shell script just exits.
Once you've seeded the generator, getting numbers in the pseudorandom sequence is easy You pull the next number in the sequence with each call to rand(). The rand() function is as easy to use as anything in the C library it takes no parameters (so you don't need to push anything onto the stack or clean up the stack afterward) and the pseudorandom number is returned in EAX.
Deleting subscribers from a configuration manager is only necessary as a way to clean up in certain unusual situations. For example, you may need to delete subscribers if a managed server goes away completely or deletes its last subscription without being able to notify the configuration manager. You then use the DELETE SUBSCRIBER command to delete all subscriptions for that subscriber (the managed server) from the configuration manager's database.
Description The MAPS Relay Spam Stopper (RSS) lists sites that are known to be open relays that have been used at least once by spammers. Open relays that have not been used by spammers are not on the RSS list. Unfortunately, a large number of legitimate sites are poorly configured, and some of these find themselves on the RSS. Fortunately, most such sites quickly clean up their servers and are removed from the RSS. The RSS therefore produces occasional false alarms.
An easy way to regain disk space is to empty the tmp folder. Like its counterpart in the Windows operating system, this is the folder in which temporary data is stored. Some applications clean up after themselves, but others don't, leaving behind many megabytes of detritus.
Because you've already downloaded the patch in a previous step, now it's time to patch the kernel source. The problem is that you have an already-compiled version of the kernel in usr src linux. That version has a known-good configuration file, but there are other files that will interfere with the patching process. Therefore, you'll need to clean up that area before patching the kernel with Grsec. Now change directory into usr src linux and clean up the source tree
Using a security-enhanced kernel such as a kernel with SELinux or a GrSecurity kernel significantly decreases the risk posed by some of the more advanced exploit techniques available. As with other security options, GrSecurity provides only one facet of a host's security. Without things like chroot, and even simply keeping the server patched, Grsec won't be as helpful. However, for all the benefits that Grsec can provide, it should be used whenever possible. It's worth the time and effort and is certainly a much better option than cleaning up after an attack that could've been prevented.
Since this is an emergency that should never really happen, we are under more or less severe time pressure. We have to cut some corners, do only the most rudimentary intermediate checks and just plan for a lengthy clean-up period when we deal with the mistakes and omissions we made. Section 25.1 explains how to set up redundant network connectivity to make this most unfortunate situation as unlikely as possible.
If you plan to pursue any of the Red Hat certification programs, don't be surprised if after some theoretical training you are given a misconfigured computer and asked to fix it. Those who get Red Hat certifications are expected to be able to clean up and repair Linux systems in the real world.
The shutdown command brings down the system in a safe way. The shutdown command issues a warning to the users and to the currently running processes so that they can clean up before the system goes down. The shutdown command then sends a run level change request to the init process. If the shutdown is intended to halt the system (option -h), the requested run level is 0. If the system is to be rebooted (option -r), the run level is 6. If the shutdown is intended to put the machine in single-user mode (neither option -r nor -h), the run level is 1.
180 this function, described in Section 220.127.116.11, does some cleaning up of the task_struct of its parent. 18.104.22.168 Cleaning up after the parent first code executed by a process when it wakes up after a context switch. It does some cleaning up of the task_struct of the previous process, in this case of its parent. Figure 8.20 Cleaning up after the parent
As disks and other local storage media get larger and larger, the amount of data that people save and keep around for an extended period of time gets equally large. Although this anecdote will date me, the first hard drive that I ever bought was a whopping 30MB and I remember thinking That should last a lifetime How can I ever fill that up It actually didn't take very long to fill the drive, and I remember having to clean up after myself frequently, writing files that I didn't really need to backup media so that I could free up space on my hard drive. Nowadays, some of my data files are larger than that entire drive, and the fact that my desktop system has access to several terabytes of storage mean that I'm less likely to clean up after myself anytime soon. It's simply easier to keep everything online (with offsite backups of truly critical data, of course). This is convenient when I want to consult an article that I wrote a decade ago about a defunct Linux distribution, but is not...
As disks and other local storage media get larger and larger, the amount of data that people save and keep around for an extended period of time gets equally large. Although this anecdote will date me, the first hard drive that I ever bought was a whopping 30MB and I remember thinking That should last a lifetime How can I ever fill that up It actually didn't take very long to fill the drive, and I remember having to clean up after myself frequently, writing files that I didn't really need to backup media so that I could free up space on my hard drive. Nowadays, some of my data files are larger than that entire drive, and the fact that my desktop system has access to several terabytes of storage means that I'm less likely to clean up after myself anytime soon. It's simply easier to keep everything online (with offsite backups of truly critical data, of course). This is convenient when I want to consult an article about a defunct Linux distribution that I wrote a decade ago, but is not...
The module initialization and clean-up functions are stored in the module instance in the .gnu.linkonce.module section. The instance is located in the abovementioned autogenerated extra file for each module. It is defined as follows12 13The macros define init_module and exit_module functions that are created as aliases a GCC enhancement for the actual initialization and clean-up functions. This trick enables the kernel to always use the same names to refer to the functions however, programmers can choose whichever names they want.
By default, any exception that isn't caught is going to produce a fatal error and halt execution of your script. PHP5 gives you a chance to clean up any uncaught exceptions with the set_exception_ handler() function. The class name, error message, and a backtrace are passed to the set_exception_ handler function, but you can also access the built-in exception class information. The function is used as follows
It is under these circumstances that a system administrator finds their responsibilities lying somewhere between deity and janitor. Ultimately, the sysadmin's job is to provide access to system resources as quickly (and equitably) as possible. This job involves both the ability to design new systems (that may or may not be rooted in solutions that already exist) and the talent (and the stomach) for cleaning up after people who use that system without any concept of what resource management really means. 19. Cleaning up after ex-users Kernel Tuning
Sometimes users can be like children, and they require a strong parent to rein them in. For instance, some users insist that they keep every file they ever used, and as a result the system disks are filled to capacity. This can be unacceptable behavior if every user did this because of the amount of time and trouble caused by having to clean up after these users. Also, since the administrator knows the system, they might need to give advice to users about how best to solve or address some particular issue or problem. For instance, a user might need to obtain a large amount of data for a particular purpose and it must be transferred from one system to another. In this case, you might need to step in and provide assistance.
If those two processes are playing nicely on your system, they'll comply with the SIGTERM signal and terminate when they're ready (after they clean up whatever they're doing). Not all processes will comply, however. A process may be hung in such a way that it cannot respond, or it may have signal handling code written to trap the signal you're trying to send. To force a process to die, use the strongest kill
Create Document Clean Up by Name Keep Aligned Paste You can place new icons anywhere on the desktop you choose. The Clean Up by Name feature reorganizes the desktop to place folder icons first, then arranges application launcher and document icons alphabetically by name. If the Keep Aligned option is selected, Ubuntu aligns any icons placed near other icons using the same spacing as when it cleans up the desktop.
Another way of forcing the umount command to do its work is to use the -f option. You can force an umount with umount -f somemount. This option is especially intended for use on an NFS or a Samba network mount that has become unreachable, and does not work on other file systems. So you will not have much success if you try it on a local file system. Another nice option, especially if you don't like to hurry, is the -l option, which performs a lazy umount by detaching the file system from the file system hierarchy and cleaning up all references to the file system as soon as it is no longer busy. Using this option lets you do an umount right away, even if the file system is busy. But it may take some time to complete.
The rcS file sets up some environmental variables, including the PATH variable. It then runs a special configuration shell script if the system is running for the first time after installation. The rcS script then runs other scripts, which do things like enable virtual memory, mount filesystems, clean up certain log directories, initialize Plug-and-Play devices, load kernel modules, configure PCMCIA devices, set up serial ports, and run System V init scripts. The rcS script will call certain scripts in etc rc.d before it relinquishes control. These include
If our server receives a termination signal from the operating system, the while loop terminates. Before exiting, we clean up our socket descriptor. As you can see, our UDP server is remarkably similar to our TCP server, except for a few major differences. First, the socket type is SOCK_DGRAM instead of SOCK_STREAM. Second, the server has to store information about the client locally to send a response, since a connection isn't maintained. Third, the server doesn't acknowledge receipt of the client's request unless we provide the code to do it.
Disk drives are very inexpensive now, so many system administrators prefer to battle the disk space problem by adding larger hard disks or extra disk drives. This option is certainly valid and prevents a lot of hassle cleaning up files, but you still should force some kind of disk space usage policy on yourself and other users to make sure disk space is not wasted. To create such a policy, you have to know how to determine disk space usage, manage disk space effectively, and clean up disks.
Each user is free to store data on the filesystem until reaching her soft limit. The soft limit implements a sort of warning zone, instructing the user to clean up while still allowing her to work. When the amount of data exceeds this limit but does not exceed the hard limit, a message is printed on the user's terminal, indicating that her quota has been exceeded however, the write operation will succeed.
Clean up the data by removing the suffixes PAGING_MB (echo TOTAL cut -d 'MB' -f1) PAGING_PC (echo PERCENT cut -d -f1) There is one part of our shell script in Listing 6.3 that we have not covered yet. At the top of the script where we define variables, I added the PC_LIMIT variable. I normally set this threshold to 65 percent so that I will know when I have exceeded a safe system paging space limit. When your system starts running at a high paging space level, you need to find the cause of this added activity. Sometimes developers do not write applications properly when it comes to deallocating memory. If a program runs for a long time and it is not written to clean up and release allocated memory, then the program is said to have a memory leak. The result of running this memory leak program for a long time without a system reboot is that your system will run out of memory. When your system runs out of memory, it starts paging in and out to disk, and then your paging space starts...
At this point, the quota tools have been installed, and the control files are in place (which we explain how to do in preceding sections). Now it's time to impose quotas. Here, we explain how to set quotas for a user name or group and how to set the grace period for users who have met their quotas and need to clean up their files.
Swap Directory Data that doesn't fit into the tile cache is stored on disk in a swap directory. The default value is .gimp-1.2, but you might want to change this to tmp or var tmp. Doing so will enable your distribution's automatic routines for cleaning up these temporary directories to remove any files that are left over in the event of a program crash. On the other hand, if space on the tmp or var tmp partition is limited, leaving the swap directory at its default may be wiser.
* Get the next available job. * struct job* next_job job_queue * Remove this job from the list. * job_queue job_queue- next * Carry out the work. * process_job (next_job) * Clean up. * free (next_job) * Carry out the work. * process_job (next_job) * Clean up. * free (next_job)
The constructor and destructor arguments to the function are optional functions (but there can be no destructor without a constructor) the former can be used to initialize newly allocated objects and the latter can be used to clean up objects prior to their memory being released back to the system as a whole.
Deborphan's ability to purge removed packages and clean up their configuration files is also helpful. Obviously, the configuration files persist for a reason, so you should be careful with this command. But if you find yourself grepping through dpkg-query output and piping to xargs too often, this one is for you
Most e-mail problems are the result of user or system administrator error. For example, the user may type an incorrect e-mail address. Misconfiguring an e-mail server causes e-mail problems. Make sure that mailboxes sit in the right directory for your distribution. If you add file system quotas to mailboxes, be aware that at some point, users may not be able to receive new messages until they (or you) clean up the mail files.
Fourth, Sun needs to clean up its marketing messages. It claims to have been founded as an open-source company . In reality, Sun was one of the companies that took UNIX into a binary distribution model. Although it is true that this model was somewhat forced by AT&T's arcane licensing strategies of the time, it was this movement of UNIX companies to restrict the source code distribution that helped motivate Richard Stallman to produce the GNU suite and the University of California Berkeley to complete the first freely distributable Berkeley Software Distribution.
This signal causes the server to close all existing connections, free all resources, and restore all defaults. It is sent by the display manager whenever the main user's main application (usually an xterm or window manager) exits to force the server to clean up and prepare for the next user. This signal causes the server to exit cleanly. This signal is used quite differently from either of the above. When the server starts, it checks to see if it has inherited SIGUSR1 as SIG_IGN instead of the usual SIG_DFL. In this case, the server sends a SIGUSR1 to its parent process after it has set up the various connection schemes. xdm uses this feature to recognize when connecting to the server is possible.
To delete the user manually, remove the user's entry from the etc passwd file. Then you can clean up the user's directories to clear disk space. You can completely delete all the user's files and his or her home directory with the command The process for manually deleting a user (or using an automated script that doesn't clean up directories and files) is as follows
No matter how big your hard drives are, at some point you're going to look at your storage and wonder where all the space went. Your home directory is probably a good example. If you are like me, you don't always clean up after yourself or organize immediately after you download a file. Sure, I have directories for organizing my ISOs, my documents and my videos, but more often than not, my home directory becomes the digital equivalent of a junk drawer with a few tarballs here, an old distribution ISO there and PDF specs for hardware I no longer own. Although some of these files don't really take up space on the disk it's more a matter of clutter when I'm running out of storage, I'd like to find the files that take up the most space and decide how to deal with them quickly. This
With both the kernel image and the kernel modules now built, we are ready to install them for our target. Before we do so, note that if you needed to clean up the kernel's sources and return them to their initial state prior to any configuration, dependency building, or compilation, you could use the following command
You may sometimes need to control elements of a module such as hardware interrupt assignments or Direct Memory Access (DMA) channel selections. Other situations may dictate special procedures to prepare for, or clean up after, a module insertion or removal. This type of special control of modules is implemented in the
Trojan Horse Programs Some programs claim to do one thing but in fact do another. For instance, a program might claim to be a tool to help you clean up unused files, but in fact e-mail your password or other sensitive data to the social engineer. An Internet-specific variant of this theme is a website that requires a password but that's run by a cracker. Because many users employ the same password on many websites, a social engineer can use the information gleaned from a fake website to
This operation is performed by end_request, a static function whose code resides in blk.h. end_request handles the management of the request queue and wakes up processes waiting on the I O operation. It also manages the CURRENT variable, ensuring that it points to the next unsatisfied request. The driver passes the function a single argument, which is 1 in case of success and 0 in case of failure. When end_request is called with an argument of 0, an ''I O error'' message is delivered to the system logs (via printk).
Compressed files are useful because they take less space on your hard disk. Another advantage is that it takes less bandwidth to send a compressed file over your network. A lot of files, such as the man pages, are stored in a compressed format on your system. Yet unpacking these to get a little bit of information and then having to compress them again is rather time-consuming. You don't want to unpack a man page, for instance, read about an option to a command and then compress the man page again. Most people will probably forget to clean up after they found the information they needed.
Employee turnover in many organizations runs high. So, unless you run a small shop with a stable user base, you need to learn how to clean up after an employee leaves. Too many so-called system administrators do not understand the stakes involved when they manage users. Disgruntled former employees can often cause significant trouble for a company by gaining access to the network.
Allow only SMTP connections that come from outside your firewall to go to those few central e-mail servers. This policy protects the other computers on your network. If your site gets spammed, you have to clean up the central e-mail servers, but the rest of your networked computers are okay.
Clean up mysql_close() The resume's header information, containing the individual's name and contact information, was handled separately from the remainder of the resume's data in order to keep the helper function pdflib_show()'s implementation as simple as possible. The body of the resume is generated by a while loop that tracks the current and previous categories, printing the category name when the value changes otherwise, it prints the description. All that remains is closing the document, returning it to the browser, and cleaning up.
Before we move on, we need to look a little more carefully at the file descriptors that are open. Up to this point you have allowed the reading process simply to read some data and then exit, assuming that Linux will clean up the files as part of the process termination.
You've done your best to clean up your code and reduce processing load in your PHP scripts, but you just can't seem to make your pages fast enough to keep your users happy. Time to throw in the towel Not quite there's more performance you can get out of your LAMP setup, and caching engines will help you do this.
If it is SIGCHLD, then it means that a child process of this one has exited. In order to clean up after it, we call sys_wait4() (see Section 9.3). The first parameter specifies synchronisation with any child process. The second parameter is a pointer to an int into which status information about the child will be written. In this case, the present process is interested only in getting rid of the zombie, so it just puts a NULL here. The third specifies not to wait for a child that has not exited. The fourth is a pointer to a struct rusage, not required in this case either. On success, this function returns the child pid, so, if there is a child process waiting, this will pick up its zombie and allow it to die in peace. The while loop caters for the possibility that more than one child may have exited it will clean up one each time around. When there is no (further) zombie, then sys_wait4( ) returns 0, and the loop terminates.
To complete our collection of memory management wrappers, we add two more functions. First, we add the function w_free_all(), which walks the list of allocated memory and deallocates the memory itself as well as the associated memory in the list. This provides us with a catchall function we can call to ensure that memory we may have neglected to free is returned to the heap. The next function, w_memory_init(), is to be called prior to using any of the other memory wrapper functions. This function initializes the global variables that the w_malloc() and w_free() functions use and registers the w_free_all() function to be called at program termination by using the atexit() system call. After a call to w_memory_init(), anytime our program exits normally, by either returning 0 or calling exit(EXIT_SUCCESS), the w_free_all() function is called to ensure we clean up all allocated memory.
In general, you want to react to attacks that you detect by preventing an attacker from gaining access to your system. If an attacker does get in, you want to get that attacker out of your system and clean up the damage as best you can. An excellent tool for detecting, logging, and denying access to your system by attackers is the PortSentry package discussed later in this chapter.
The best way initially to get involved in a project is to identify and fix bugs, clean up code, and so on. By reading all the information on the project's site and chatting with the other developers, you'll soon get an idea of where the project is headed and can nominate yourself for a specific task to help achieve that goal.
As before, if we run into any problems writing to the client, we close the socket and continue listening for other connections. Once our file has been sent, we'll clean up the file descriptor and close the second socket. Our server will loop back and check for more connections on socketl until it receives a termination signal from the operating system. Once the termination signal is received, we'll clean up by closing the original socket (socketl), and exiting.
Cron Three entries exist for cron (two daily and one hourly). The two daily entries, in etc cron.daily, clean up the news service (remove old entries) and check that the news service is working once a day. The one hourly cron entry checks that the news service is running and then sends news articles to other NNTP sites.
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Is your home bursting at the seams with stuff? Is every closet crammed so full that any one of them is a death trap waiting to be opened? Has it been years since the last time you parked the car in the garage? Never fear, help is on the way. You need to get rid of some of that stuff. Dont you dare call it junk. Remember, one man or womans trash is another ones treasure!