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With CPUs faster, memory larger disk caches can also be larger increasing number of read requests can come from cache thus, most disk accesses will be writes LFS Strategy structures entire disk as a log have all writes initially buffered in memory periodically write these to the end of the disk log when file opened, locate i-node, then fin...

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Telling the programs to use less energy may mean poorer user experience Examples change from color output to black and white speech recognition reduces vocabulary less resolution or detail in an image

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Virtual memory and I/O occasionally interact Proc issues call for read from device into buffer while waiting for I/O, another processes starts up has a page fault buffer for the first proc may be chosen to be paged out Need to specify some pages locked exempted from being target pages

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Algorithm to allocate a resource may be to give to shortest job first Works great for multiple short jobs in a system May cause long job to be postponed indefinitely even though not blocked Solution: First-come, first-serve policy

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Separate what is allowed to be done with how it is done a process knows which of its children threads are important and need priority Scheduling algorithm parameterized mechanism in the kernel Parameters filled in by user processes policy set by user process

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Mainframe operating systems Server operating systems Multiprocessor operating systems Personal computer operating systems Real-time operating systems Embedded operating systems Smart card operating systems

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While the log files found in /var/log may be extremely helpful for troubleshooting problems, they might become a problem themselves if they fill up the filesystem. Having services like mail and printing available may be useful, but if they cause your system to crash, then that can be a problem. Mounting /var on a separate partition is often done ...

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To display the current umask value, execute umask with no arguments. To set umask to a value of 027, type umask 027 The new umask value will only apply during a login session. When a new shell is started, your default umask will be in effect again. To set a new default umask, modify ~/.bashrc The umask value has no effect on existing files or ...

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Use the userdel command to delete a user account. By default, only the account is deleted, not any of the files owned by the user. By using the –r option, files in the user’s home directory and the user’s mail spool are deleted.

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Displays detailed user and system information: [sysadmin@localhost ~]$ w 10:44:03 up 50 min, 4 users, load average: 0.78, 0.44, 0.19 USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT root tty2 - 10:00 43:44 0.01s 0.01s -bash sysadmin tty1 :0 09:58 50:02 5.68s 0.16s id sysadmin pts/0 :0.0 09:59 0.00s 0.14s 0.13s who sysadmin pts/1 example.com 10:00...

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