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Apr
28
awarded  Popular Question
Apr
28
comment How filesystem atomically writes a block to disk?
What kind of atomicity guarantees are you interested in? Generally speaking, only sectors can be considered to be atomic in storage; a partially written sector will result in FEC failure when read back so you'll get an I/O error (if the write proceeded too far to recover the previously written data). If you want more than that, and this is unrelated to the issue of physical write alignment, you should be reading up on journaled file systems.
Apr
28
comment How filesystem atomically writes a block to disk?
That is not guaranteed when the size of data to be written does not equal the sector size. When the size of data to be written is identical to the sector size and the write is properly sector-aligned, you can generally trust that the write is fully atomic, but if it fails part-way through (for example due to an unfortunately timed power outage) the sector will later come back as unreadable, not as a mix of old and new data.
Apr
15
comment storing ssh remote executed command output to variable is blocking. connection not ending?
You may want to quote the $dir expansion, lest you might run into problems if $dir ever expands to a path that contains whitespace or shell metacharacters.
Apr
12
comment On Linux, when does “uptime” start counting from?
I'm pretty sure the time stamp you see at the top of the log from the boot is the time when the syslog daemon received the message to be logged. That's not the same thing as when the system was powered on, or even the same thing as when the kernel was initialized.
Apr
12
revised On Linux, when does “uptime” start counting from?
Incorporate from comments to answer
Mar
30
answered Is it possible to name a part of a command to reuse it in the same command later on?
Mar
29
comment How to allocate available HDD from /home to /root
Please be mindful of the difference between the file system root (/) and the directory /root (which is traditionally the home directory for the root user).
Mar
29
comment Can I run an application using a different libc version?
To summarize the accepted answer to the question linked to by skwllsp, looks like VMs is a much easier way to go.
Mar
26
accepted Make fetchmail leave mail on server for a specified period of time?
Mar
21
awarded  Popular Question
Mar
10
comment bit rot detection and correction with mdadm
@caveman A birthday attack against SHA-256 would have a probability of 2^-128 (on the order of 10^-38) of succeeding. For a non-intelligent adversary, that's likely your worst case scenario. And that's beyond the disk's ability to detect errors (which protect you against some but not all failure scenarios). I'll take those odds. If you want to discuss this further, please post a new question about it on an appropriate site instead of continuing a conversation in comments to a largely unrelated answer.
Mar
10
comment bit rot detection and correction with mdadm
@caveman I don't know about you; I really like the fact that I don't have to constantly checksum files just to be certain that they haven't been corrupted. Sure, the huge majority of the time there is no corruption, in which case no harm's done (with ZFS, you get your pick of checksum algorithm among a handful, so you can pick your preferred point along the security/performance continuum), but automated file system level checksums guarantees that there is no uncorrected corruption because if there is, you will know about it, in ZFS' case by receiving an I/O error instead of corrupted data.
Mar
7
comment Why is the password I entered not visible?
Keyboards tend to make some amount of noise as they are used, which can be heard or recorded for later analysis to determine password length. Some keyboard models are quieter than others. Also, some keys tend to make relatively distinct noises (think space bar, Enter, etc.). In this context, also consider How critical is it to keep your password length secret? on Information Security.
Mar
7
comment Why is the password I entered not visible?
There are ways to execute a command without it being stored in the command history. See for example Execute command without keeping it in history.
Mar
1
comment Set vsftpd user to use specific folder only
What FTP server is this about?
Feb
28
comment On Unix systems, why do we have to explicitly `open()` and `close()` files to be able to `read()` or `write()` them?
@jamesqf Well, not exactly a few hundred feet above the surface, but something very similar actually did happen on Apollo 11. The Eagle LM guidance computer restarted multiple times during late descent in response to processor overload conditions.
Feb
26
revised On Unix systems, why do we have to explicitly `open()` and `close()` files to be able to `read()` or `write()` them?
Better title
Feb
26
comment On Unix systems, why do we have to explicitly `open()` and `close()` files to be able to `read()` or `write()` them?
@jamesqf We did send people to the Moon with fairly similarly spec'd hardware. Granted, the AGC wasn't the only computer used for the missions, let alone the entire Apollo program...
Feb
26
comment How do I list installed packages with source URI, distribution and section in Debian?
See also: List all software installed from particular component (non-free, contrib)