37
votes
Accepted
What command can I use to clear the 'yum' cache, on Fedora 23 system?
According to the documentation for dnf clean:
Performs cleanup of temporary files kept for repositories. This includes any such data left behind from disabled or removed repositories as well as for ...
- 8,384
31
votes
How to cache or otherwise speed up `du` summaries?
Common usage of du can be immensely sped up by using ncdu.
ncdu - NCurses Disk Usage
performs the du, caches the results and shows them in a nice command line GUI, somewhat comparable to du -hc -d 1 | ...
- 411
31
votes
Accepted
Why does Chromium not cache DNS for more than a minute?
Chromium/Chrome does not cache DNS requests more than a minute indeed.
Interestingly enough, from bugs-chromium - Issue 164026 - DNS TTL not honored from Apr 21 2011
The only DNS cache in the system ...
- 56.8k
27
votes
Make Linux write to network filesystem concurrently with local disk reads
After some more investigation, it looks like this issue is less kernel related and more about how rsync and CIFS interact.
As far as I can make out, what is happening is that when rsync closes the ...
- 6,903
24
votes
Accepted
30% of RAM is "buffers". What is it?
What is the difference between "buffers" and the other type of cache?
Why is this distinction so prominent? Why do some people say "buffer cache" when they talk about cached file ...
- 50.3k
23
votes
How to cache or otherwise speed up `du` summaries?
duc
(see https://duc.zevv.nl) might be what you're looking for.
Duc stores the disk usage in a optimized database, resulting in a fast user interface. No wait times once the index is complete.
...
- 231
19
votes
How to flush the DNS cache in Debian?
If using systemd-resolved as your DNS resolver (i.e. the hosts line of your /etc/nsswitch.conf file includes the word resolve and/or /etc/resolv.conf contains the line nameserver 127.0.0.53), then ...
- 209
17
votes
Accepted
How to clean yum cache for untracked repositories?
The yum clean all command actually suggests that you run rm -rf /var/cache/yum:
» yum clean all
Cleaning repos: amzn2-core amzn2extra-docker amzn2extra-epel copr:copr.fedorainfracloud.org:jdoss:...
- 2,519
15
votes
Accepted
Make debian "apt" (new apt-get / aptitude frontend) cache .deb files in '/var/cache/apt/archives/'
Create a /etc/apt/apt.conf.d/01keep-debs file with the following content:
Binary::apt::APT::Keep-Downloaded-Packages "true";
Your *.deb should be kept in /var/cache/apt/archives/* directory.
Or ...
- 66.8k
15
votes
Accepted
Why were "USB-stick stall" problems reported in 2013? Why wasn't this problem solved by the existing "No-I/O dirty throttling" code?
The 2013 article is wrong
A mistake in LWN? Are you sure?
Long queues in I/O devices, created by "background" writeback
Limitations of "no-I/O dirty throttling"?
Genuine reports of ...
- 50.3k
13
votes
Accepted
What happens when a file that is 100% paged in to the page cache gets modified by another process
Continuous release then replaces /apps/EXE with a brand new executable.
This is the important part.
The way a new file is released is by creating a new file (e.g. /apps/EXE.tmp.20190907080000), ...
- 21.8k
12
votes
Accepted
Is "Cached" memory de-facto free?
That view can be very misleading in a number of real-world cases.
The kernel now provides an estimate for available memory, in the MemAvailable field. This value is significantly different from ...
- 50.3k
11
votes
Can I safely remove /var/cache?
Found this post interesting in that I was looking to delete from /var/cache on Ubuntu 15.10 for disk space improvement, this is what I have found:
/var/cache/apt cache files are removed after 'sudo ...
- 111
11
votes
Defer *all* disk writes, keep them in memory
If you want to prevent disk writes as much as possible, you can do this with Laptop Mode. One of the features of laptop mode is to allow a disk to spin down and to prevent the kernel from writing to ...
11
votes
Accepted
What is an alternative for zcache?
Indeed zcache appears to have been discontinued, as it was removed from kernel 3.11 for being effectively obsolete. The commit message of zcache removal reads
staging: zcache: delete it
zcache ...
- 1,112
11
votes
Accepted
Does a tmpfs (/dev/shm) use Linux Page Cache? If it does, then how?
Does a tmpfs use Linux Page Cache?
tmpfs and the page cache are two sides of the same coin.
As described in https://www.kernel.org/doc/Documentation/filesystems/tmpfs.txt (emphasis mine)
tmpfs ...
- 49.2k
11
votes
How to clean yum cache for untracked repositories?
There is another option available:
# yum --enablerepo='*' --verbose clean all
Here it's explained:
# man yum
...
CLEAN OPTIONS
The following are the ways which you can invoke yum in clean mode.
...
- 590
10
votes
How to check when yum metadata will expire?
yum repolist enabled -v contains this information (the metadata_expire configured and the last metadata update time) and pretty output.
[root@localhost ~]# yum repolist enabled -v | grep 'Repo-name\|...
- 111
9
votes
How can I transparently cache any directory or mounted file system for reads and write back?
Try using catfs, a generic fuse caching filesystem I'm currently working on.
- 211
9
votes
Accepted
Can I easily make a host "mirror" that caches downloaded Debian packages?
For having a local deb cache to server my Debian server farm, I actually prefer to use apt-cacher-ng (caching proxy server for software repositories)
It is a proxy specially APT/deb aware, quite ...
- 56.8k
9
votes
Accepted
Why does closing a file wait for sync when overwriting a file, but not when creating?
That sounds like a reminder of the O_PONIES fiasco, which just recently had its 11th birthday.
Before ext4 came, ext3 had acquired a sort of a reputation for being stable in the face of power losses. ...
- 139k
8
votes
Accepted
Checking a URL redirection from terminal
curl has the -L option
-L, --location
(HTTP) If the server reports that the requested page has moved to a different location (indicated with a Location: header and a 3XX response ...
- 1,703
8
votes
Accepted
kernel: FS-Cache: Duplicate cookie detected - what is this?
This appears to be working as intended. The Duplicate cookie detected errors are not indicative of a situation that requires action by the sysadmin.
As has been pointed out on the upstream bug ...
- 18k
8
votes
Accepted
What is good block size for file cache on Linux?
The device block size is the block size with what the system is talking with the HDD controllers. If you want to read/write the HDD, it happens so:
Read:
CPU -> HDD controller: "Please send me the ...
- 9,731
7
votes
How to read the local DNS cache contents?
If you are using nscd, you can view the contents (and possibly some other garbage), by showing the ASCII strings from the binary cache file. In Debian/Ubuntu, that file is /var/cache/nscd/hosts for ...
- 171
7
votes
Accepted
dirty_ratio per device
dirty_ratio per device
Q: Are there any ways to "whitelist" the fast devices to have more write cache? Or to have the slow devices (or remote "devices" like //cifs/paths) use less write cache?
...
- 50.3k
7
votes
Why is my system using swap when RAM fills up with cache?
You can set the swappiness to 0.The Linux documentation says:
"This control is used to define how aggressive (sic) the kernel will swap memory pages. Higher values will increase aggressiveness, ...
- 4,688
6
votes
how to check default cache mode for disk in kvm
Here is a way to check some default cache mode. Although it's also kind of documentation, it's "online" and you get the default cache mode of your current QEMU version. As @dokotr5000 said, it depends ...
- 171
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