Prologue
Sorted by alphabetical order of the name of the packages
FUSE
df: ‘/home/shendi_zl/iso/mnt’: Transport endpoint is not connected
Incorrect operation will cause some problems to the mount point mounted by FUSE, and something like Transport endpoint is not connected will occur.
Solution
No need for root privilege.
fusermount -uz mount_point
Reference
Updated at 12 Apr, 2022
Nautilus
Nautilus is slow when opening directories
In Ubuntu, too many Template files can cause nautilus to slow down. Keep files in the ~/Templates directory only if necessary.
Reference
Update at 7 Oct, 2022
NFS
nfs: server mu01 not responding, still trying
When part of the file system is mounted as NFS, if the ssh login and auto-completion are slow and dmesg shows nfs: server mu01 not responding, still trying, it is possible that the user’s IO is too frequent and heavy, which makes the NFS host unable to process it in a timely manner. And we can figure out the user by package capture by using tcpdump: applying:
tcpdump -i eth0 -s 0 -w /tmp/tcpdump.pcap host server.example.com
Where eth0 is the network interface that used to communicate between NFS client and host, /tmp/tcpdump.pcap is the location you want to store the captured package, server.example.com is the hostname of NFS host.
Wait for a while, the program can be terminated by press ^C, and the tcpdump.pcap file could be open by Wireshark. Applying the filter shown in the red circle, you may notice a UID appearing frequently. This UID may be the one who causes problems, try to determine its username from /etc/passwd and fix it.
Reference
Update at 22 Jan, 2024
SSH and SSHD
Users cannot login Linux host with pubkeys via ssh but root user can do so
When login a Linux host via ssh, some hosts requests your password even if the public key is added in ~/.ssh/authoirzed_keys correctly, and the permission of the corresponding directory and files are set properly.
By checking the /var/log/{secure,audit/audit.log}, we found out that SELinux denied the key. And our normal hosts disabled the SELinux, so we decided to disable the SELinux by:
setenforce 0
To make the setting permanent, we edited the /etc/selinux/config as following:
# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
# enforcing - SELinux security policy is enforced.
# permissive - SELinux prints warnings instead of enforcing.
# disabled - No SELinux policy is loaded.
SELINUX=disabled
# SELINUXTYPE= can take one of three values:
# targeted - Targeted processes are protected,
# minimum - Modification of targeted policy. Only selected processes are protected.
# mls - Multi Level Security protection.
SELINUXTYPE=targeted
The setting will be enforced after rebooting.
According to Wikipedia:
For example, SELinux requires a filesystem that supports “security labels”, and thus cannot provide access control for files mounted via NFS.
As SELinux provided a deny default (or whitelist) policy, when the access policy (or other policies) isn’t set, SELinux will deny the behavior by default.
Our /home is mounted via NFS (a disk from another machine). Maybe this is the reason that why root, whose ssh-related files are in /root, which is mounted directly,
/dev/mapper/centos-root on / type xfs (rw,relatime,seclabel,attr2,inode64,noquota)
can login via keys on a machine protected by SELinux, but other users, whose ssh-related files are in /home/username, which is mounted via NFS,
mu01:/home on /home type nfs (rw,relatime,vers=3,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=12.12.12.100,mountvers=3,mountport=20048,mountproto=udp,local_lock=none,addr=12.12.12.100)
cannot login via keys on the same machine.
Reference
public key authentication fails ONLY when sshd is daemon
Why am I still getting a password prompt with ssh with public key authentication?
How to Disable SELinux on CentOS 7
Update at 27 June, 2023
Users & Groups
Users/Groups exist (which can be switch in by su) but cannot be found in /etc/{passwd, shadow, group}
Try to figure out the content in /etc/nsswitch.conf.
For example, if the following contents are in nsswitch.conf:
passwd: files nis sss
shadow: files nis sss
group: files nis sss
It means that user and group information can be stored in three places: files (/etc/{passwd, shadow, group}), nis (Network Information Service) and sss (System Security Services). You can find exact which database the information in by using getent passwd -s {files, nis, sss}, respectively(The curly brackets “{}” means select one from the set in it).
Reference
Linux manuals.
Update at 15 May, 2023
