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Full Discussion: virtual memory
Top Forums UNIX for Dummies Questions & Answers virtual memory Post 85608 by RTM on Thursday 6th of October 2005 09:36:02 AM
Old 10-06-2005
Virtual memory: The use of a disk partition or a file on disk to provide the same facilities usually provided by RAM. A way of using disk storage space to make the computer work as if it had more memory. When a file or program is too big for the computer to work with in its memory, part of the data is stored on disk. This virtual storage is divided into segments called pages; each page is correlated with a location in physical memory, or RAM. When an address is referenced, the page is swapped into memory; it is sent back to disk when other pages must be called. The program runs as if all the data is in memory.

RAM: Random Access Memory. The working memory of the computer. RAM is the memory used for storing data temporarily while working on it, running application programs, etc. "Random access" refers to the fact that any area of RAM can be accessed directly and immediately, in contrast to other media such as a magnetic tape where the tape must be wound to the point where the data is. RAM is called volatile memory; information in RAM will disappear if the power is switched off before it is saved to disk.
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SYSTEMD-CRYPTSETUP-GENERATOR(8)                            systemd-cryptsetup-generator                            SYSTEMD-CRYPTSETUP-GENERATOR(8)

NAME
systemd-cryptsetup-generator - Unit generator for /etc/crypttab SYNOPSIS
/lib/systemd/system-generators/systemd-cryptsetup-generator DESCRIPTION
systemd-cryptsetup-generator is a generator that translates /etc/crypttab into native systemd units early at boot and when configuration of the system manager is reloaded. This will create systemd-cryptsetup@.service(8) units as necessary. systemd-cryptsetup-generator implements systemd.generator(7). KERNEL COMMAND LINE
systemd-cryptsetup-generator understands the following kernel command line parameters: luks=, rd.luks= Takes a boolean argument. Defaults to "yes". If "no", disables the generator entirely. rd.luks= is honored only by initial RAM disk (initrd) while luks= is honored by both the main system and the initrd. luks.crypttab=, rd.luks.crypttab= Takes a boolean argument. Defaults to "yes". If "no", causes the generator to ignore any devices configured in /etc/crypttab (luks.uuid= will still work however). rd.luks.crypttab= is honored only by initial RAM disk (initrd) while luks.crypttab= is honored by both the main system and the initrd. luks.uuid=, rd.luks.uuid= Takes a LUKS superblock UUID as argument. This will activate the specified device as part of the boot process as if it was listed in /etc/crypttab. This option may be specified more than once in order to set up multiple devices. rd.luks.uuid= is honored only by initial RAM disk (initrd) while luks.uuid= is honored by both the main system and the initrd. If /etc/crypttab contains entries with the same UUID, then the name, keyfile and options specified there will be used. Otherwise, the device will have the name "luks-UUID". If /etc/crypttab exists, only those UUIDs specified on the kernel command line will be activated in the initrd or the real root. luks.name=, rd.luks.name= Takes a LUKS super block UUID followed by an "=" and a name. This implies rd.luks.uuid= or luks.uuid= and will additionally make the LUKS device given by the UUID appear under the provided name. rd.luks.name= is honored only by initial RAM disk (initrd) while luks.name= is honored by both the main system and the initrd. luks.options=, rd.luks.options= Takes a LUKS super block UUID followed by an "=" and a string of options separated by commas as argument. This will override the options for the given UUID. If only a list of options, without an UUID, is specified, they apply to any UUIDs not specified elsewhere, and without an entry in /etc/crypttab. rd.luks.options= is honored only by initial RAM disk (initrd) while luks.options= is honored by both the main system and the initrd. luks.key=, rd.luks.key= Takes a password file name as argument or a LUKS super block UUID followed by a "=" and a password file name. For those entries specified with rd.luks.uuid= or luks.uuid=, the password file will be set to the one specified by rd.luks.key= or luks.key= of the corresponding UUID, or the password file that was specified without a UUID. rd.luks.key= is honored only by initial RAM disk (initrd) while luks.key= is honored by both the main system and the initrd. SEE ALSO
systemd(1), crypttab(5), systemd-cryptsetup@.service(8), cryptsetup(8), systemd-fstab-generator(8) systemd 237 SYSTEMD-CRYPTSETUP-GENERATOR(8)
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